Safety Biker : When To Replace A Helmet / Safety Tips 007

Summary:

• Did you crash it? Replace immediately. 
• Did you drop it hard enough to crack the foam? 
• Replace. Is it from the 1970's? Replace. Is the outside just foam or cloth instead of plastic? Replace.
• Does it lack a CPSC, ASTM or Snell sticker inside? Replace. 
• Can you not adjust it to fit correctly? Replace!!

Did you crash in it?
For starters, most people are aware that you must replace a helmet after any crash where your head hit. The foam part of a helmet is made for one-time use, and after crushing once it is no longer as protective as it was, even if it still looks intact. Bear in mind that if the helmet did its job most people would tell you that they did not even hit their head, or did not hit their head that hard. And the thin shells on most helmets now tend to hide any dents in the foam. But if you can see marks on the shell or measure any foam crush at all, replace the helmet. (Helmets made of EPP foam do recover, but there are few EPP helmets on the market. Yours is EPS or EPU unless otherwise labeled.)

You can also crack the helmet foam or damage it by dropping the helmet on a hard surface. The cracks may be small and hard to see, so you need to look carefully. Cracks in the foam always require replacement of the helmet.

You may be reluctant to replace a helmet that looks almost as good as new, but if you did hit, you don't want to take chances on where you will hit next time. If the foam is cracked under the thin shell, it will be more likely to fly apart in your next crash. Many manufacturers will replace crashed helmets for a nominal fee, and most will also inspect crashed helmets to see if they need replacement. Call them if you are in doubt. For contact info check our list of manufacturers. (You can also ask them if they think the advice on this page is valid!} Is it from the 70's?

If you still have a helmet from the 70's without a styrofoam liner, replace it immediately. That would include the Skidlid (with spongy foam), 1970's Pro-tec (spongy foam), Brancale (no foam) and all leather "hairnets." They just did not have the protection of helmets made after 1984 when the ANSI standard swept the junk off the market.

The better 1970's helmets were reasonably good ones, but were not quite up to current standards. It is probably time to replace that old Bell Biker, Bailen, MSR, Supergo or similar model from the 70's or early 80's. (We have a page up on replacing the Bell Biker.) The hard shells were great, but the foam liners were not thick enough to meet today's ASTM or Snell standard. The Bell V-1 Pro was designed to today's standards, but the foam is very stiff, and if you are over 65 you probably should replace that too. If you have one of the 1980's all-foam helmets with perhaps a cloth cover, we would recommend replacing that one. Lab tests showed some years ago that bare foam doesn't skid well on pavement, and could jerk your neck in a crash. The cloth doesn't help much. In addition, some of them had no internal reinforcing, and they tend to break up in a crash. That's not serious if you just fall, but if you are hit by a car the helmet can fly apart in the initial contact and leave you bare-headed for the crack on the pavement.

Is it newer? With what standards sticker inside?

Newer helmets from the late 1980's and the 90's may or may not need replacement. First look to see what standards sticker is inside. If it's ASTM or Snell, the helmet was designed to meet today's standards for impact protection, and you may even find that Consumer Reports tested it in one of their articles. Most manufacturers now recommend that helmets be replaced after five years, but some of that may be just marketing. (Bell now recommends every three years, which seems to us too short. They base it partially on updating your helmet technology, but they have not been improving their helmets that much over three year periods, and we consider some of their helmets since the late 1990's to be a step backwards, so we would take that with a grain of salt.) Deterioration depends on usage, care, and abuse. But if you ride thousands of miles every year, five years may be a realistic estimate of helmet life. And helmets have actually been improving enough over time to make it a reasonable bet that you can find a better one than you did five years ago. It may fit better, look better, and in some cases may even be more protective. For an alternate view that agrees with the manufacturers, check out the helmet FAQ of the Snell Foundation. Snell knows a lot about helmets and their views on this subject should not be dismissed lightly, even though we disagree with them.
Occasionally somebody spreads rumors that sweat and ultraviolet (UV) exposure will cause your helmet to degrade. Sweat will not do that. The standards do not permit manufacturers to make a helmet that degrades from sweat, and the EPS, EPP or EPU foam is remarkably unaffected by salt water. Your helmet will get a terminal case of grunge before it dies of sweat. Sunlight can affect the strength of the shell material, though. Since helmets spend a lot of time in the sun, manufacturers usually put UV inhibitors in the plastic for their shells that control UV degradation. If your helmet is fading or showing small cracks around the vents, the UV inhibitors may be failing, so you probably should replace it. Chances are it has seen an awful lot of sun to have that happen. Otherwise, try another brand next time and let us know what brand faded on you.
At least one shop told a customer that the EPS in his three year old helmet was now "dried out." Other sales people refer to "outgassing" and say that the foam loses gas and impact performance is affected. Still others claim that helmets lose a percentage of their effectiveness each year, with the percentage growing with age. All of that is nothing but marketing hype to sell a replacement helmet before you need it. There is some loss of aromatics in the first hours and days after molding, and helmet designers take account of that for standards testing. But after that the foam stabilizes and does not change for many years, unless the EPS is placed in an oven for some period of time and baked. The interior of your car, for example, will not do that, based on helmets we have seen and at least one lab crash test of a helmet always kept in a car in Virginia over many summers. Helmet shells can be affected by car heat, but not the foam. The Snell Memorial Foundation has tested motorcycle helmets held in storage for more than 20 years and found that they still meet the original standard. EPS is a long-lived material little affected by normal environmental factors. Unless you mistreat it we would not expect it to "dry out" enough to alter its performance for many years.

An honest manufacturer: MET

The Italian company MET says in their 2010 catalog: "We are often asked 'For how long is a helmet safe?', or 'how often should I replace my helmet?”' Until now it has been difficult to find any reliable figures to help answer these queries. MET have now developed a series of tests which are conducted on aged helmets to determine a 'best before' date (unless the helmet is involved in an accident. In that case it should be replaced immediately.). The results indicate that, if used properly accordingly to our owner manual, our helmets will still do their job up to eight years after they have been made. Not only is that good news for the customer, it’s great news for the environment!"

We applaud MET for undertaking an actual testing program on helmet life and for making that statement. We regard it as a triumph of integrity over marketing. MET's helmets are made with industry standard shells and liners, so there is no reason we can see that their recommendation should not be good for many other helmet brands as well. If another manufacturer comes up with a testing program that shows earlier deterioration in the protection from their products we will review this page.

In sum, we don't find the case for replacing a helmet that meets the ASTM or Snell standards that compelling if the helmet is still in good shape and fits you well. Are you using it for non-bicycle activities?

Since 2003 helmets have been available that are actually certified to skateboard or ski standards as well as the CPSC bicycle helmet standard. If you are using a bicycle helmet for skateboarding or any other sport where you crash regularly, see our writeup on helmets for the current season for more info on that.

Otherwise, we would recommend buying another helmet designed for the activity you are pursuing, whether or not you replace your bike helmet. We have more on that subject on our page on other helmets. Note that most "skate-style" helmets currently on the market are actually bicycle helmets certified only to the CPSC bicycle helmet standard. They have CPSC stickers inside, but no ASTM Skateboard standard sticker. Do you still like wearing it?

Your helmet is of course a piece of wearing apparel as well as a safety appliance. If you consider yourself a stylish rider and your helmet is not as spiffy as the new ones, go for it. There is nothing wrong with wanting to look good, and if you do, fashion is a valid reason to replace a helmet.
Is it a better helmet than the ones available today?

As new styles have become more "squared-off" and designers have begun adding unnecessary ridges and projections that may increase the sliding resistance of a helmet shell, there is good reason to stay with one of the more rounded designs of the early to mid 90's. Those round, smooth shells like the original Bell Image that Consumer Reports rated highly in 1993 are more optimal for crashing than some of the newer designs. So think twice about "moving up," and look for a rounded, smooth-shelled design when you do. We have a lot of info on the new ones up on our page on helmets for the current season.
Inspecting a Helmet
We have a page up with step by step instructions on how to inspect a helmet.

Safety Bicycle Helmet Inspection For Biker 03

Inspection

You need to look at the helmet's main elements: Outside Shell

The exterior plastic of a helmet is important to hold it together in a crash. Look first for cracks or abrasion on the surface that show evidence of an impact. Even if you think the helmet has never been impacted, look carefully. Many riders don't know they hit their head. Small cracks around the edges or anywhere else on the shell indicate aging and a need to replace.

Press carefully all over the helmet to see if you get a "beer can" effect where the shell can be pushed in and it pops back. Most cheap helmets show some of that when new, but that should be all over the helmet, and very little. If the shell dents more than a little bit, that indicates crushed foam underneath, and a need to replace. If there is crushed foam you would usually see abrasion of the shell where it indents. Note that more expensive helmets that are molded in the shell should have no beer can effect whatsoever. With those helmets any flat spot on helmet surfaces that were formerly curved would indicate damage.

Check the shell color for fading. The helmet below was ridden across the US by Brian Hanson. It was vibrant yellow when he started. With constant sun exposure it faded badly, probably from lack of sufficient UV inhibitors in the plastic. If your helmet fades, the plastic has probably become brittle, and it should be replaced. Brian replaced his.

Liner

Remove the fitting pads if they come out, and inspect the styrofoam liner carefully for any signs of cracks or compressed foam. If in doubt about a spot on the helmet, measure the foam thickness and that of an identical spot on the other side, or if you have another helmet of the same model and size, use that. If you discover any cracked or crushed foam, replace the helmet. Remember that EPS liners do recover some of the crushed thickness, but the foam that was compressed will not perform well in the next hit. Even if you find no damage, if you know the helmet has taken an impact you should replace it. The damage can be difficult to identify even with careful measuring.

If you have one of the few bike helmets with an EPP (Expanded PolyPropylene) or other multi-impact liner, do the inspection as described above anyway. EPP recovers, but not 100%. In time if you crash more than once you will find foam damage and need to replace your helmet.

Buckle and Strap

Check the straps on the helmet for signs of wear, and replace if they seem worn, faded or any of the stitching is beginning to fail. Salt accumulations should be washed out before inspection. Check the buckle and replace if you see any missing parts. The plastic blades that lock into the female side of most buckles can break. The buckle will hold together weakly with one blade, but will fail in a crash.

Rear Stabilizer

The rear stabilizer on many of today's helmets is not really part of the retention system that holds the helmet on the head, but a means of adding some stability for comfort. It should still be inspected for structural integrity and to be sure the adjustment is working. Stretching or tugging it with moderate force will usually tell you that.

Standards Sticker

Some older helmets had impact protection as good as anything on the market today. If yours has a CPSC, ASTM or Snell sticker in it and passes the other inspection points, it is probably still a good helmet. If is is older than that, it should be replaced.

More on replacement

We have a page up on when you need to replace a helmet, with more detail on what makes it necessary.

Rentals

In addition to cleaning a helmet when it is returned, the inspection steps are critical for renting. Many riders will not tell you when they crash, or will not think they hit their heads. With experience the steps above can be quickly done, but you must remember to do them each time.

Checklist

Here is the info on this page as a helmet inspection checklist. in .pdf format for printing out.

Biker Safety : Bicycle Night Visibility And Lights

The Question

>I was wondering about solutions for *BICYCLE* visibility at night.

The Response:

I have used many devices over the years, since I commuted for about 20 years and still ride a lot at night. I started with white bicycles, then tried 3M's glass bead reflective paint. It looked great under headlights but was dull otherwise. I am now using neon orange bikes, and may go to neon lime green. I think all of those approaches are improvements over a standard dark frame, since seeing a frame identifies the vehicle immediately as a bicycle, at least from the side and some other angles.

The concept you have to keep in mind is that you want to establish your identity as you catch the driver's eye so they know what you are. Motorcycle research shows that if you want to be seen on a motorcycle there is one thing that beats daytime headlights, orange vests, flags, big windshields or any other device -- be a cop! It turns out that drivers usually see a police motorcycle. We have asked motorcycle cops and they agreed, although there are exceptions. So you are not just trying to catch an eye. You are really trying to register on a driver's brain that you are a vehicle moving on the road, and establish that you are a bicycle so that the driver has some idea of what your speed and position on the roadway are likely to be. Often you are doing that in the midst of incredible urban light clutter from other vehicles, traffic signs, streetlights, commercial signage, porch lights, windows and many other sources.

For headlights I use a car light. Nothing makes a driver respond quicker, even in the midst of urban light clutter, since they are conditioned from childhood to look for oncoming cars, and at night that means they are looking for oncoming car lights. The little bike lights may be bright, but they look like a pinpoint, and can just get lost among all the other light sources in the background. Car lights have a cutoff beam that does not blind others on a trail, and puts the light on the roadway where you need it.

The nicads to run my car light were heavy and required charging every night, but they were cheap from surplus sources. For years I used D cells from power packs for an NEC 386 laptop. Then I converted to NiMH batteries, and tried using C cells due to the higher energy of NiMH cells, but went back to D cells eventually because the C's just did not seem to hold up and lost capacity. I used 11 (NiMH)or 12 (NiCad) cells rather than ten to provide extra voltage and keep the light bright. Again, the cheap NiMH D cells did not hold up that well in daily use, and I now have to charge that battery almost continuously to have it work. In the fall of 2006 I started phasing in a 5.5AH Powerizer Lithium Ion / Polymer battery that weighs 18 oz (500gr), puts out 14.7 volts for a very bright headlight and may melt down some day the way lithium cells sometimes do when cell protection circuits fail. The vendor says "for R&D use only and NOT for individual customers." I charge it in my bike parking area and use it while riding outdoors, so that's a concern but seems like a reasonable risk similar to those that laptop users are running. I am looking for one in the safer LiFePO4 chemistry that self-extinguishes if a protection circuit fails.

For tail lights I started with two leg lights, showing red to the rear and white to the front. Those have the advantage of going up and down, attracting attention and identifying the bike. But they are visible only on one side, so for a while I used two of them. I still use one sometimes as an identifier. I added yellow blinkers, starting with a 7 inch barricade light. Those are ideal for bikes, since they attract attention by the blink, have a big reflective band around them, and are identified in a car driver's mind with stationary objects on construction sites, so they grab a driver's attention. As with any blinking light, the blink saves a lot of electrical power, since the light is mostly off. The fresnel lens is very efficient, and the bulbs are designed to resist tremendous vibration from passing trucks. I run my 6 volt ones from a 9v alkaline cell or from NiMH AA or C cells. Their only disadvantage is the size and weight, but if you are still hung up on that you just have not ridden enough at night.

After the barricade light I added smaller yellow blinkers. The best was something called the Far Out Flasher, sold by Schwinn stores in the 80's and by the late Ed Kearny (Bicycle Lighting Systems). The Belt Beacon was another, and I used those on my helmet, mounted with Velcro, juiced up by adding chrome tape to make a reflector behind the bulb. Yellow is still the best color for a flasher, since the population is aging, and red eyesight gets dim as eyes age.

I have tried turn signals, but never felt that they were really recognized by the motorist. The rack-mounted ones are too close together to give much of a directional indication. I tried one back in the 1980's that attached to my wrist and blinked only when the arm was raised, but you would need two of those, and again I had no way to know if the motorist behind me knew what the blinker represented or not, since they had probably never seen one before. That idea was revived in 2008 and updated with LED's by Safe Turn in Australia. They seem to have disappeared, but others have new ones out.

Beginning about 1990 I added the now-standard red LED blinkers, since they had taken over as the light signature of a bicycle and that increases the probability of being identified early as a bike. I had one on my helmet, mounted with hook-and-loop. Their only problem is that they are too small, and to a driver small means far away, so the car may not realize how close you are. There are some improved LED lights out now, that I first saw at the September, 1999, Interbike show, including a Vista that has "wings" with 15 LED's in the center and five in each adjustable wing. Vista also has a standard size tail light with multiple LED's that is very bright, but costs $60 and is designed to plug into their rechargeable system. At the same show I bought a very large LED flasher being test-marketed at a Chinese exporter's booth designed for use by cars as an emergency road flasher, and packaged as a "Highway Safety Light." It is 4" x 6", and has 18 extremely bright LED's in three rows. It's called the Fast Field Model HW-18, and it cost me $10, probably the dealer price. The light runs on 4 AA cells, with a claimed life of "at least 25 hours" which is about what I get from it. It looks like the biggest, brightest led flasher you have ever seen. But it had no bike mount, so I had to make one from aluminum bar stock. I have one now on all the bikes we ride at night. It is heavy for an led light, at 9 oz. with the batteries. It was hard to find at first, since they are imported in car parts channels, but our local Target had them for while, and now there are at several sources on the Web. Not all of them are equal, and some are disappointly dim. One decent one is probably the Real Light by Necessary Options. It even comes with brackets for mounting on a bicycle.

In December of 2001 I got an email from an importer who claims that his product is not only the bright version but has bike mounts. It is sold only through bike stores, so you have to go to your local LBS and hope they have them. I don't know how to tell you how to distinguish the high output ones from the low output ones, so you are on your own.

I have replaced the incandescent blinking Far Out Flasher on my helmet with an Innova 24/7 led blinker. This is an octagonal light about 2" by 3" (50mm by 75mm) that velcros on well. It runs on a CR123 lithium primary cell. It is not approved for lithium rechargeables, but could run on two NiMH 1/5 AA cells. The CR123's are expensive in stores but cheap on the Web, and one lasts me for many night rides. The light has a rectangular LED area with a rotating switch that selects different blink patterns and colors of LEDs. I use the one that flashes rapid red then white then yellow and looks vaguely like a police car flasher.

I got a sample at Interbike of a single yellow led that screws onto a shraeder valve and goes around. It uses hearing aid batteries. Another one introduced in 2002 has flashier led blinkers, but they are smaller. Either model adds to rotating weight right at the rim and uses an expensive battery. Saw another good idea at Interbike--a string of LED's that you weave around the spoke nipples. They are doubled up, with one facing each side, and about 8 inches apart on the rim. When the wheel turns fast enough (over 15 mph) it creates a ring of fire. It runs on two AA cells in a holder zip-tied to the spokes near the hub. I installed mine on my night bike and it looked great! They were available from Mr. Happy's Galactic Tracers under the trade name RimLites, but I don't see their Web site any more. I had problems with the battery contacts, and the instructions say don't use it in the rain (!) Mine self-destructed when I got a stick in the spokes, and I am not using them any more. Somebody was also exhibiting a "Whale Tail" led blinker for helmets. I tried a small high-output red led flasher on my helmet to replace my old yellow Belt Beacon. It is attached with hook-and-loop. At present I am using an Inova 24/7 light on my helmet. It has red and white leds that blink in a very bright emergency light pattern, and runs happily for months on one CR2 photo battery.

In 2004 I sent for a Californeon helmet light. It's a neon-like band about a quarter inch (7mm) wide that goes around the helmet and sticks on with a 3M adhesive. The battery pack takes a 9 volt battery and clips on your belt. Looked ok in the basement shop, but the circuit board burned out in less than 10 minutes of use, and before I had a chance to see what it would look like outdoors.

In general, I believe in redundancy, with at least two of everything just like a car. Redundant filaments in my car headlight let me use the high beam with a handlebar trigger flasher as a warning or passing through short tunnels, and also would provide an emergency option if the low beam ever dies. (Car lights have a very long filament life.) Redundant tail lights are essential, since nobody has ever produced a completely reliable light for a bicycle. I also like to "layer" my tail lights, with one at the level of the wheel axle, one under the saddle, and one on the helmet. The more I observe about urban light clutter the more I favor big, big lights and lights that have a signature. You will find this concept better developed on Ken Kifer's Web page discussion of the Flashing Neon Light Display, although I would not favor his use of a diesel generator to power the array.

In 2010 the battery powering my car light failed once again and I bought a new Magicshine system from Geoman Gear. It is LED powered and uses a Soul P7 SSC LED with four led's on one die. The heat sinking is adequate, and it lights up the road. Unfortunately, it lights up a lot of other territory as well, and can blind people coming the other way if not adjusted carefully. On trails I push it downward when people approach. I use two of them. The original batteries were recalled, and I have the new replacement. If this light had a shaped beam with a sharp cutoff above the pavement it would be ideal.

Those who ride off road at night have found helmet-mounted lights useful. If you use one, be sure to mount it with hook-and-loop or the kind of breakaway mount developed by Jet Lites. And please don't flash your light in my eyes on a dark trail.

There is now a category of lights called LED flares. They are designed for traffic situations. They should be durable. I have not seen them in use yet.

Some things can help in addition to the active lights that you should primarily rely on. For reflectors I use the hottest 3M product I can lay my hands on to add reflectivity to pedals, shoes, cranks (flashes as the cranks go around), panniers, clothing, helmet, anywhere else. 3M markets a "snake" in Europe that weaves around the spoke nipples, and under headlights looks like a ring of white, identifying the bike immediately. The 3M demo video is very impressive. I am trying a similar product now from a company called Techflex. Their product is called Reflex, and was originally developed for electricians to make electrical cables in big buildings easy to find and trace. They sell it for brake cables, but other than adding a point of light I don't think that helps identify a bicycle very well. As a round circle in your wheel, however, it can be much more effective. I am using one on the front wheel of my night bike, but my panniers obstruct it in the rear.

You can find 3M Scotchlite in many local stores, but for their hotter stuff, you have to go to the Web to places like Itendi-tape. Be prepared to spend more, but the results are pretty impressive. I use it on helmets and some other spots, even though it adds only points, not an identifying signature.

Unfortunately, all reflective products depend on being in the beam of a headlight to have any light to reflect, so for a lot of situations they are not much help. But I frequently find that flashing pedal reflectors are my first warning that a cyclist without a headlight is approaching on a dark trail.

Flags are great for daytime. I use two on my recumbent. One has a blinking white strobe light on the top of the shaft. The blink of a strobe disappears too fast for the eye to follow it well, but combined with the flag it's better, and it gives a 360 degree flash. I asked a more experienced recumbent rider if his flag slowed him down. He said he did not know, but maybe, and for sure he felt slower with the flag.

Safety Google : Chainsaw

This article is about risk control methods specific to chainsaws and chainsaw operations. Chainsaws incorporate numerous safety features common to many engine-driven power tools. Manufacturers have invented numerous design features to improve safety. Some features have become de facto standards, and others are legal requirements in particular jurisdictions. Best practice dictates that an operator should inspect the saw before starting work and only operate the saw if all the safety features are properly functional.

Additional safety features are a significant commercial advantage to chainsaw producers. Companies continue to develop new features over time. Most chainsaw safety features are focused on the kickback problem, and seek to either avoid it (chain and bar design), or to reduce the risk of injury should it occur (chain brakes). In addition to the safety features built into the chainsaw, operators should also wear specific chainsaw safety clothing. Most older saws have few or none of these features, and extra care should be taken in their use.

Chain

The chain has to be properly matched to the guide bar and the saw. Chainsaw manufacturers specify a selection of suitable chains for each model of saw.

Best safety requires that the chain is properly sharpened. One key sharpening parameter is the depth gauge setting. The depth gauge is the small steel protuberance in front of each cutting tooth. The difference in height between the leading cutting edge and the depth gauge determines the thickness of the wood chip taken by the cutter. If the depth gauge is too low, the cutter takes too deep a bite from the wood, the saw becomes difficult to control and the chances of kickback increase.

Some chains also have guard links in front of each cutter link. The guard link reduces the tendency of the leading edge of the depth gauge to snag on small-diameter objects such as small branches, or to engage with ordinary timber if forced into contact with it.

Chainsaw bars

Kickback reduction

Chainsaw Kickback is primarily caused by cutting with the chain in the "kickback zone" on the bar, the upper quarter of the nose.[1] Some saws, usually electric saws intended for domestic garden use, shield this whole area from contact with a "tip protector". All cutting produces a reaction force on the saw: normally this should be the lower edge of the bar, where the chain is travelling towards the saw and the reaction tends to pull the saw safely towards the log, against the spur dogs. Where the chain is moving downwards, as at the tip of the bar, the same reaction force now acts upwards and will cause a kickback upwards.

Tip protectors are metal or plastic devices that fit over the bar tip and are usually fitted to small, domestic-class saws. While these are effective, they hamper the saw in terms of the type and capacity of cuts it can execute, and are not widely used. They find a useful application in pole pruners and one-handed battery-powered saws that are used for trimming, hedge laying etc. The hooked nose of the tip protector can be used to "grab" branches for cutting, and presents no great drawback since these very small saw units are not used for cuts where the bar tip is buried.

Carving bars

Chainsaw carving often makes deliberate use of plunge cuts, and cuts on the tip of the bar. By simply reducing the diameter of the chain nose, the amount of chain, and thus the force generated during a kickback, may be reduced. Specialist carving bars are available with small pointed noses.

Chain brake

Front handguard, and combined chain brake lever

Chain brakes prevent movement of the saw's cutting chain by applying a steel brake band around the driven clutch drum.[2] Clamping force for the brake band is provided by a powerful spring. The chain brake has two purposes. First, it can be used to secure the chain when changing position, moving between cuts or starting a cold saw, which requires a partly open throttle. This would otherwise lead to uncontrolled chain movement, a major hazard in older saws. Secondly, the chainbrake can activate under kickback conditions to prevent the operator from being struck by a running chain. Of course being struck by even a static chain may cause serious injury, but anything that can be done to mitigate the usually dreadful injuries caused by contact with a moving chain is of obvious benefit to operators. Kickback injuries usually occur to the head, face, neck and shoulders; when a running chain is involved, such injuries are usually very serious, often disfiguring and sometimes fatal.

The chain brake is principally operated by the top-hand guard being pushed forward to engage the brake, and pulled back to disengage. The spring-loaded action allows powerful braking under emergency conditions and can halt a chain under full power in a fraction of a second. Correspondingly, it may require considerable force to reset.

The chain brake may be activated deliberately by the operator, or automatically by the force of a kickback event. In the former, the operator usually rotates his left wrist and knocks the top hand guard forward with the back of his hand, re-setting it by reaching forward with his fingers to pull the top hand guard backwards. In the case of a kickback event the operator's left hand may be violently dislodged from the handle and the top hand guard will be thrown onto his hand, forcing activation of the chainbrake. Husqvarna models also incorporate a link between the top handle and the chain brake trigger, applying the brake if the saw's bar is forced suddenly upwards. This is known as an "inertia" chainbrake and will allow activation of the chainbrake even if the operator's left hand is not removed from the handle.

The chain brake may also be of use when sharpening a chain on a bar, as it allows robust filing to take place without the chain slipping about.

"Wrap-around" top-hand guards have made an appearance in recent years, but are unpopular.[who?] They restrict movement, and make no allowance for the fact that when the handle is gripped on the lower section of the handle (left side of the saw from the operator's viewpoint) it is usually for making lateral, right-to-left cuts. In this situation the operator's head, neck and shoulders are out of the cutting plane of the saw and will not be struck even if a kickback does occur.

Chainsaw kickback

Chainsaw kickback can occur when the tip of the bar comes into contact with a relatively massive or immovable object with the chain under power. The area of the bar tip most likely to be involved is known as the "kickback quarter". looking from the side of the bar, the kickback quarter is the 90° section of bar found between a line going along the centreline of the bar, and another line at 90° to the first, rising upwards from the centre of the nose sprocket. If this area of chain comes into contact with - for instance - a log, the chain will initially cut the wood, but will also produce a reaction force which pushes the bar upwards. As the bar rises, the chain is forced harder into contact with the wood and climbs upwards even harder. In a fraction of a second the chain may jam hard into the wood and hurl the bar upwards towards the operator, often causing very severe injury or death. The violence of a full kickback event is such that no evasive action is possible, and if the operator's head, neck or shoulders are in line with the plane of the bar, he will certainly be struck by it. At this point, he must rely on his chainbrake and PPE to save him from injury or worse.

Another form of kickback may occur where the top of the bar is used for cutting and becomes suddenly pinched by the wood moving. In this case the saw may be forced backwards towards the operator, or forced into a position where the tip is pinched and the saw transitions into a classic tip-driven kickback. Kickback may also occur as a result of a failed or improperly executed boring cut. Bore cutting is a specialised technique requiring proper training, and should not be attempted without such training.

Kickback reducing systems

By far the most effective tool in preventing kickback is operator training. By preventing contact between the bar tip and solid objcts, kickback may be avoided. By keeping their head and body out of the cutting plane of the bar, injury may be prevented if kickback occurs. A useful tip is that if the operator can't read the logo on the side of the bar, they are too close to the cutting plane and should lean left to ensure safety.

Correct chain sharpening is paramount to safety in this context. Blunt chain cuts poorly and leads to increased operator fatigue and increased bar loading. Depth gauges filed too low make the chain grab at the wood and may negate the benefits offered by safety chain.

Chain design plays a major part in kickback reduction. Older, non-safety designs carried only teeth and depth gauges. Since these present a solid leading edge at the depth gauge should an object be suddenly forced into the chain, they can easily be made to engage fully with the foreign body and launch into a full kickback. Careful filing of the depth gauges, making a radius down to the leading edge, reduces the risk somewhat. Newer chains with ramped drive links fill in the gap ahead of the depth gauge, reducing the tendency to grab still further. Full safety chains have extra bumper links between the cutting links, maintaining nearly full depth gauge height along the full extent of the chain and reducing the risk of kickback to very low levels. Full safety (bumpered) chains are often fitted as original equipment to domestic and entry level saws. Modern "professional" chains offer far higher cutting performance than full safety chain, and offset their increased risk with an assumption of a much higher degree of operator competence. In reality they are still safer than traditional chains due to the vastly improved depth gauge design, with a deep ramp ahead of the gauge point.

Bar design is another factor in reducing kickback risk. The larger the radius of the bar tip, the greater the risk of kickback as the degree of engagement with the log (or other body) will be greater for a larger tip. Domestic class bars, climbing saw bars and entry-level professional bars usually have very small tips. Professional bars designed for logging and felling may have much larger tips as they are often used for boring cuts to free trapped timber or fell difficult trees, and a tapered, small-tipped bar will wedge easily when boring, stalling the chain. A large-tipped bar with nearly parallel sides bores easily and does not tend to jam.

While kickback prevention is a great concern in the context of chainsaw use, it is not the only means by which an operator can be injured by a saw. Local conditions, operator competence and many other factors need to be considered before undertaking sawing operations.

Safety throttle

The engine throttle is operated by the trigger under the rear handle of the saw. Unless the lock-out switch above the rear handle is also pressed, the throttle cannot move from the idle position, and the chain will not be driven.

The safety throttle prevents the chain from being driven if the trigger is accidentally pushed by an obstruction, such as a branch in undergrowth. It also prevents throttle activation when hot-starting a saw on the ground with one boot inside the rear handle. The safety throttle is an additional layer of protection in this case, since the chainbrake should be applied before starting a saw in any context.

The pictured model has an enlarged lock-out or 'dead man' switch which, when released, also activates the chain brake, thus instantly halting the running chain as well as disengaging the throttle.

On/Off switch

The on/off switch stops the engine running by preventing the ignition coil from firing. It must be clearly marked with the stop position. There must be a positive click action, so that there is no chance that the switch will change position accidentally, even while the saw is vibrating under heavy load.

If the switch were to move to the off position while the operator was in the middle of a critical cut while felling a tree, there would at least be a delay, which increases the chance that the tree might fall in an uncontrolled manner. Also, the saw might jam in the cut, requiring that the operator spend extra time under the unsafe tree freeing it. A switch failing "on" would also present a hazard, since the saw may then start inappropriately, such as when testing compression or assessing starter function.

If the operator is injured while using the saw, a bystander might have to move in to turn the saw off. The bystander may be unfamiliar with the saw and needs to be able to identify the on/off switch by its markings.

The Stihl model shown combines the choke, throttle start setting and ignition switch into one unified control lever. Other brands of saw usually have separate controls for all three, or a combined throttle start setting and choke control with a separate ignition switch.

If the switch fails to operate, a saw may be reliably stopped by operating the choke control to flood the engine.

Centrifugal clutch

The centrifugal clutch disengages the chain from the engine when the engine is only at idling speed, engaging the drive automatically when the throttle is squeezed and the engine is at full speed. The purpose of this clutch is to avoid having a moving chain when the saw is idling and temporarily not cutting. At idle the chain should not move.

Many rear-handled chainsaws are used in a state, owing to poor maintenance, where there is some clutch drag and so the chain does move slowly at idle. For top-handled saws though, this is extremely dangerous and the clutch (and chain brake) on such a saw must always be functioning correctly.

Some early chainsaws used a manual clutch instead, but this is long obsolete. Anti-vibration system rubber bush metal spring

Excessive vibration over long periods can cause the user to develop hand-arm vibration syndrome (HAVS), or white finger. This is a potentially permanent and debilitating industrial injury. To reduce vibration, saws are divided into two parts. One part is a rigid assembly of the cutter bar and engine. This part vibrates strongly when the chain is cutting. The other part is a rigid assembly of the handles and controls of the machine, the part the user holds. These two rigid assemblies are joined together by mounts which provide spring suspension and damping.

Both metal springs and rubber bushes can be used to provide suspension. Metal springs are more robust and longer wearing, but rubber bushes provide damping in addition to a spring action.

Many modern saws incorporate electrically heated handles. This can help prevent HAVS by encouraging circulation to the fingers. Husqvarna models with this option have a "G" suffix after the model number.

Rear handle

Rear-handled chainsaw and two-handed grip

The front and rear handles of a typical "rear handle" chainsaw are widely spaced,so as to provide enough leverage for good control,[6] and also to provide some degree of control in the event of a kickback.

The operating controls of the chainsaw, such as the throttle and the engine stop (or on/off) switch, are placed so that they may operated whilst retaining a good grip on the rear handle.

It is impossible to use a rear-handled chainsaw single-handed. Their balance is such that this is not merely unwise, but so impractical as to be beyond a reasonable chance of it even being attempted.

Top-handled chainsaws

Top-handled chainsaws are a form of chainsaw whose safety is deliberately compromised in order to permit them being used single-handed where this is essential. They are restricted to working at height, such as up a tree.In all other cases, it should be possible to arrange the cutting task so that it can instead be carried out with two hands and the safer rear-handled chainsaw.

In the top-handled saw, the rear handle and its operating controls are moved to the top of the saw.This gives a balance to the saw such that it can now be used one-handed. The front handle remains the same. The chain brake lever is usually separate, rather than being combined into the protective hand guard.

In most cases, the top-handled chainsaw is used two-handed.It is only used single-handed when this is essential, such as when one hand is required for climbing.At ground-level, top-handled saws should not be used.

Owing to the nature of work at height, and the difficulty of continually re-starting the saw, the engine will often still be running when it is not used for cutting at that moment. For this reason it is particularly important that the centrifugal clutch is operating correctly so that the chain doesn't rotate when the engine is idling.The chain brake should also be engaged manually when not actually required,which is why top-handled saws usually have an easy brake control lever.

In many jurisdictions, use and even purchase of top-handled chainsaws is restricted to those holding the relevant certificate of competence in their use.

Rear hand guard

The rear hand guard protects the users right hand from being struck by a snapped or derailed chain.It also allows the rear of the saw to be held down by the operator's boot for starting. This is especially useful for cold engines, and larger (70 cc+) saws.

Exhaust

The exhaust directs the hot and noxious gases coming from the engine away from the user. A faulty exhaust increases noise, decreases engine power, can expose the user to unsafe levels of exhaust gases, and can increase the chance that the user could accidentally touch extremely hot metal. Most models feature a spark screen which is integrated into the muffler. The spark screen prevents sparks from being discharged from with the exhaust and potentially igniting sawdust. The spark screen also reduces noise.

Hand/Eye/Ear Defender Symbols

Warning labels

In the EU at least, it is a legal requirement that chainsaws carry certain standardized warning labels which warn of the dangers of kickback as well as making clear the need for protective clothing.

Scabbard

The cutter chain is sharp enough to cause injury even when it is not being driven. The scabbard covers the chain when the saw is in storage or being transported. It also protects the chain from damage, for instance blunting by contact with concrete floors.

Safety: Fire Fighter Clothing Or Bunker Gear Information

Bunker Gear or "Turnout Gear" are terms used by many firefighters to refer to their system of outer protective clothing. "Bunker gear" and "turnout gear" can refer, depending on the context, to just the trousers and boots, and jacket, or the entire combination of personal protective equipment and personal protective clothing. The terms are derived from the fact that the trousers and boots are traditionally kept by the firefighter's bunk at the fire station to be readily available for use. This clothing is usually referred to as Fire Kit in the UK and Ireland. In Hong Kong it is referred to as incident gear.

Historically, firefighters did not have the same level of protective clothing used today. Because of this most fires were fought from the outside of burning buildings, and structures were rarely entered. Early in the history of firefighting, a firefighter's outer clothing were more for warmth and dryness than for protection from fire. In the early 19th century, felt caps were worn of various design and were more for decoration than service, this early headgear did not provide any protection against flame or head injury but did keep water off the firefighter's face. The forerunner of the modern firefighter's helmet was developed in 1830 by a luggage maker Henry Gratacap who was a volunteer firefighter in New York City. He saw a need for a better designed helmet that was both functional and provided protection to the wearer. This helmet is immediately recognizable today as the "New Yorker" style and little has changed in its general shape. The helmet had a high peaked front to retain a helmet shield which was usually adorned with a company name and number and it also featured eight rib sections on the dome (for added rigidity) and a long rear brim that channeled water away from the wearer's neck.

The early use of long trench coats, made of leather or canvas and later made of rubber, was the forerunner of modern turnout jackets. Early coats had felt or wool liners to provide warmth in the winter. These liners later developed in basic thermal protection liners found in today's modern coats. Earlier rubber coats were much longer than today's modern turnout jackets, reaching down to a firefighter's mid thigh and were worn with long rubber boots called "three-quarter boots" which came above the firefighter's knees. This interface of boot and coat left a large gap of protection against fire. This system has since been replaced by the modern combination of a jacket, pants with suspenders, and shorter rubber or leather boots, although some departments still wear the traditional old style of gear.

The combination of modern triple-layer turnout gear with self-contained breathing apparatus (SCBA), PASS device, and modern communications equipment made it more feasible and survivable to enter burning buildings. Modern turnout jackets and pants are made of fire resistant fabrics (mainly Aramids such as Nomex and Kevlar) or polybenzimidazole (PBI) fibers The standard that the National Fire Protection Association has designated to firefighter protective clothing, NFPA 1971: Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting, which specifies "the minimum design, performance, safety, testing, and certification requirements for structural fire fighting protective ensembles and ensemble elements that include coats, trousers, coveralls, helmets, gloves, footwear, and interface components.

Station uniform

The first component of firefighting equipment is the uniform that a firefighter will wear around the station. Its purpose is to provide a comfortable clothing that they wear around the station, but will not become an obstruction when a firefighter is required to put on his turnout gear. Naturally, turnout gear is to be worn over the station garments during any call that a firefighter is called upon. Another aspect of the station uniform is the station safety shoes, commonly referred to as work boots. These shoes are required to be fitted with safety toes and puncture-resistant soles in most countries in case the firefighter goes out on a call that does not require his/her turnout gear.

United States

The United States follows NFPA 1975, Standard on Station/Work Uniforms for Fire Fighters. NFPA 1975s main purpose is that no part of the uniform garment “ignite, melt, drip, or separate”[1] when exposed to a heat of 500°F for 5 minutes.

Turnout clothing

Turnout clothing can consist of a combination of trousers with a overall strap attached, boots, and a jacket. Most fire services seem to use a trouser/jacket combination. The advantage of this combination is the ability to take off the jacket in situations where the jacket is not necessary. Since bunker gear insulates the body from the outside air the body heats up rapidly, taking off a jacket helps considerably in keeping cool.

Materials

According to NFPA 1971 and similar standards in other countries, all turnout clothing must have three components: an outer shell, a moisture barrier, and a thermal barrier. In between these layers are pockets of air referred to as "dead zones". These layers of air along with the three protective layers help to further insulate the wearer from the extreme environments of fires. Usually turnout pants are outfitted with reinforced knees and leather cuffs.

The materials used for the three layers in turnout trousers and coats may vary but will very often include a Nomex/Kevlar combination of material. As an example, the materials used by the Los Angeles City Fire Department, as found in their 2005 recruit handout are as follows:

Outer Shell: Southern Mills, Advanced, Nomex/Kevlar blend in a "Rip stop Weave", with water repellent finish.

Thermal Insulated Layer: Southern Mills Caldura Batten Quilt Material. Thermal and Moisture barriers are sewn together for removal for cleaning, repair and replacement from Outer shell.

Moisture Barrier: Breathe-Tex material combined with Nomex/Kevlar blend laminated cloth.

NFPA 1500 (Primary Guidelines for the Fire Service) and similar standards mandate features such as protective collars and sleeves to protect the fire fighter from exposure to heat, (hot or polluted) water and debris :

Turnout trousers

Once the need arises for actual firefighting protective equipment to be worn, also known as turnouts, a firefighter must properly wear protective equipment required. Turnout trousers will be the first article of clothing that a firefighter will usually wear. Suspenders worn with the turnout trousers should be the heavy duty type in order to stand up against such heavy weights and rigorous activities they will face. Most experienced interior firefighters (firefighters that enter the structure in an emergency) will carry, in their turnout trouser pockets, various tools and equipment as well as rope they may need during an emergency. The turnout trousers, when not in use, are usually stored scrunched down around the boots for efficient and fast access when they are needed. The firefighter may then step into each boot and pull up the trousers and suspenders.

Turnout coat

A turn out jacket

A turnout coat is the type of jacket typically worn by firefighters. Oversized pockets allow for carrying tools and equipment, and reflective safety stripes ensure that firefighters remain visible to each other. Protective coats will usually have Velcro or zipper functions which will enable a firefighter to properly and efficiently don this piece of gear. There is also a storm flap which covers this closure area and protects it against damage and loosening and as an extra measure to the fire fighter as these areas can be exposed to fire and heat. Wristlets, 4 inch (according to NFPA 1500) 100% Nomex coverings along the distal end of the coat arms in with the thumb joint will slip through, fit around the firefighter's hand and provide redundant protection where the skin may show between the glove and coat. They are designed to prevent burns to the wrist, while preventing bunching and remaining flexible.

Overall

The overalls that are available are of the same materials and specifications. Usually an overall has a cord built in around the waist to make it fit better. Because of its size it's more difficult to scrunch up the overall around the boots.

Boots

Several pairs of surplus firefighter boots.

Firefighter turnout boots are usually sized as a regular shoe, but are made of rubber or leather with a Boron Steel toe insert. The boots are slipped inside the legs of the trousers to maintain a barrier from the heat given off by the fire. When the trousers and boots are not being actively used, the trousers will fold down and out around the shins of the boots, ready for quick access for the firefighter. Due to the enormous amounts of potential hazards at a fire scene to the feet, turnout boots are required to be able to handle a variety of different burns and blows. All boots are required to be outfitted with safety toes and a puncture resistant midsole plate to prevent puncture from sharp objects that may be stepped on. Such emphasis on the midsole plate is made that IFSTA has deemed that “if there is doubt about midsole protection, [one should go as far as to] x-ray the boot.” Flash hood/Nomex hood and other parts of the garments A firefighter wearing the face-piece component of an SCBA with Nomex hood

When helmets do not provide built-in protection for the ears, neck and part of the face a protective firefighting hood is worn by firefighters. These are fitted and designed to protect the firefighter’s ears, neck, and the parts of his face which are not protected by the SCBA mask.

They are designed to the guidelines set by NFPA 1975. Cal/OSHA Title #8 also has regulations in the state of California. They are made of Nomex Knit Fabric which weighs 6 oz./ Sq. Yrd.; they are most often double ply with only one seam running from the top center of the face opening, over the top and down the bottom of the bib. The Nomex Knit, which is standard, is why they are commonly referred to as Nomex hoods. First, the hood is tucked into the collar. The SCBA mask is then donned, and the hood pulled over the face seal to cover any exposed skin.

Firefighter helmet Main article: Firefighter's helmet The firefighter's helmet is built to withstand falling objects and high heat.

The fire helmet's first function was to shed water in early years. Today, it is first and foremost designed to protect a firefighter from falling debris and injury to the head while fighting a fire. The secondary job of the fire helmet is to protect from heat, and hence burns to the head. It provides a hard shell, electrical, heat, and steam burn protection, and in some types of helmets, goggles or a visor. Goggles or a visor are used to protect the firefighter's eyes during rescue and extrication operations. Fire helmets are constructed of various materials including non conductive materials for protection against electrical currents, carbon fiber and plastic combination for a lightweight design for comfort, and a Kevlar lining for strength and protection.

The design of helmets vary from fire service to fire service and depends on the service or department's requirements. Some helmets are fitted with a face guard or shield to protect the firefighter's face against heat, dust, water and debris when working on a rescue or extraction call as well as when performing fire exposure protection. In the case of exposure protection the shield works better for it keeps more heat from the firefighter's face, but the goggles give more eye protection in extraction and rescue ops.

United States

There are four basic components to firefighting helmets:

Helmet shell: Well balanced, lightweight, and designed to provide maximum protection. Contains a Front Brim (provides protection to "eyes and facial" area), Rear Brim (Protection to "neck" from debris and water run-off), and Raised Top (Provides stability from impact from above).

Impact ring: 3/8" thick sponge rubber Impact Ring to absorb impact energy Helmet liner: High Density plastic liner, made of fire retardant cotton and nomex; completely adjustable; "NAPE Strap" adjusts to firmly cradle the occipital portion of head.

Chin strap: 3/4" wide, black nylon w/ Velcro on one end, leather backed "postman" side buckle. The leather helps protect the skin of the cheek from the metal buckle. Previous types of helmets had been constructed of a steel outer shell with a ribbed construction for extra strength and compressed cork with a lacquer applied to the outer face of it. The design and shape of the helmet is intended to redirect water and debris from the head and neck area. It also prevents head or neck injury to the firefighter in the event of falling debris.

Colors

Some departments, such as the Los Angeles City Fire Department (LAFD) use the helmet color to identify officers and functions and is listed as follows per www.lafd.org

White : Chief Officer (Chief, Assistant Chief, Battalion Chief)

Orange : Captain I and Captain II (Reflective tape blue under the helmet number is a Captain I "Engine Captain" / Red is a Captain II "Truck Captain"

Yellow : Firefighter, Firefighter/Paramedic, Engineer, Apparatus Operator, Probationary Firefighter NO FRONT SHIELD

Red : Arson

Blue : Paramedic Single function non fire suppression certified or Firefighter Cadet/Intern

Yellow Helmet with Green Numbers : Specialized companies Hazardous Materials, Urban Search and Rescue, Fire Boats

Black : Fire Explorers (now called Fire Cadets)

Orange Helmet with Green Numbers : Captains of the specialized Companies

The New York City Fire Department (FDNY) issues a black helmet to all ranks except those of Battalion Chief and up. These officers receive a white helmet. The FDNY uses the front shield of the helmet to distinguish both company number and the function of that company. The following colors denote function in the FDNY:

Black : Engine Company

Red : Ladder Company

Blue : Rescue and Hazardous Materials Company

Yellow : Squad Company

Green : Marine Units

Orange : Probationary Firefighter

The Houston Fire Department uses a combination of colored helmets and colored leather shields and colored coat striping to distinguish rank and function.

Black: Firefighter and Engineer/Operator(E/O) with a black shield, Incident Command Technicians (ICT) also known as "Chief Chauffeur's" have a white shield

Red : Captain with a red shield (Engine Captains) and a white shield for Senior Captains (Ladder Truck Captains).

White: District Chiefs and above. Also all FF,E/O's and ICT's have yellow reflective on the bunker coats. Officers from Capt to Chief have red reflective.

Certain styles of helmets do not lend themselves to the use of leather helmet fronts. Typically these helmets use crescents on the side to distinguish function. These crescents come in a wide variety of titles and are usually reflective in nature.

In most cases here in the United states the colors will be as follows Fire chief, Assistant chief, Deputy Chief, Battalion chief : white Captain and LT's: red or yellow and vice versa. Engineers: red or black Firefighters: black in most cases, yellow at some departments Probationary: Orange, yellow Safety officer: Blue explorers and Jr's: Green and Yellow

Europe

In Europe and some Europe-oriented countries around the world the helmet designs vary from the U.S. designs in that they are moving towards a style without brims. The pilot-style helmets have a brim at the front of the helmet, and a shape that covers more of the head. The neck is protected by a combination of a Nomex (or similar material) flash hood, and a foil-faced neck curtain which connects to the rear of the helmet. In most designs the nomex fabric also protects the area around a SCBA facepiece and the front of the neck. A commonly used helmet is the F1 helmet although several other designs like the Dräger HPS Helmet are in use.

These helmets tend to have in-built face protection (visors) and eye protection that swivel into the shell of the helmet for protection.

EN 443:1997 (Helmets for firefighters) specifies the properties that are demanded for protection, comfort and durability. There are optional specifications to cater for national requirements. The new EN 443-2008 now replace the EN 443-1997.

Hand protection

There are many types of hand protection which are available to firefighters today, the most common being the work glove and the structural firefighting glove.

Work gloves are a must for all fire services. They are used when gloves are required, but actual firefighting gloves are not. They allow better mobility to perform various types of functions from relaying hose beds to vehicle maintenance.

Work gloves are usually made of leather or a leather-like material.

Extrication gloves are similar in design and appearance to auto mechanic's gloves but are made of a heavier rip-proof and puncture-resistant material such as Kevlar while still lightweight enough to allow the manual dexterity to operate rescue equipment and sometimes enough to take a victim's pulse. These are used in urban search and rescue, vehicle extrication and related applications, but are not rated for firefighting.

For an actual working fire, structural firefighting gloves must be worn. Structural gloves tend to be the last piece of protective equipment to be donned; usually because the free dexterity of the fingers are required to perform functions such as properly placing an SCBA mask on and accurately tightening a helmet strap. The gloves will fit over the wristlets and under the distal part of the coat sleeve, ensuring full enclosure of the latter arm. Gloves are designed to protect from extreme heat, various penetrating objects, and to allow dexterity. Usually the latter is sacrificed in order to give adequate protection to heat and sharp objects. Newer gloves are more lightweight and don't lose their dexterity when they dry after becoming wet, the way leather gloves may.

Seo safety : Smoke Detector

A smoke detector is a device that detects smoke, typically as an indicator of fire. Commercial, industrial, and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible or visual alarm from the detector itself.

Smoke detectors are typically housed in a disk-shaped plastic enclosure about 150 millimetres (6 in) in diameter and 25 millimetres (1 in) thick, but the shape can vary by manufacturer or product line. Most smoke detectors work either by optical detection (photoelectric) or by physical process (ionization), while others use both detection methods to increase sensitivity to smoke. Sensitive alarms can be used to detect, and thus deter, smoking in areas where it is banned such as toilets and schools. Smoke detectors in large commercial, industrial, and residential buildings are usually powered by a central fire alarm system, which is powered by the building power with a battery backup. However, in many single family detached and smaller multiple family housings, a smoke alarm is often powered only by a single disposable battery.

History

The first automatic electric fire alarm was invented in 1890 by Francis Robbins Upton (U.S. patent no. 436,961). Upton was an associate of Thomas Edison, but there is no evidence that Edison contributed to this project.

George Andrew Darby patented the first electrical Heat detector and Smoke detector in 1902 in Birmingham, England.

In the late 1930s the Swiss physicist Walter Jaeger tried to invent a sensor for poison gas. He expected that gas entering the sensor would bind to ionized air molecules and thereby alter an electric current in a circuit in the instrument. His device failed: small concentrations of gas had no effect on the sensor's conductivity. Frustrated, Jaeger lit a cigarette—and was soon surprised to notice that a meter on the instrument had registered a drop in current. Smoke particles had apparently done what poison gas could not. Jaeger's experiment was one of the advances that paved the way for the modern smoke detector.

It was 30 years, however, before progress in nuclear chemistry and solid-state electronics made a cheap sensor possible. While home smoke detectors were available during most of the 1960s, the price of these devices was rather high. Before that, alarms were so expensive that only major businesses and theaters could afford them.

The first truly affordable home smoke detector was invented by Duane D. Pearsall in 1965, featuring an individual battery powered unit that could be easily installed and replaced. The first units for mass production came from Duane Pearsall’s company, Statitrol Corporation, in Lakewood, Colorado. These first units were made from strong fire resistant steel and shaped much like a bee's hive. The battery was a rechargeable specialized unit created by Gates Energy. The need for a quick replace battery didn't take long to show itself and the rechargeable was replaced with a pair of AA batteries along with a plastic shell encasing the detector. The small assembly line sent close to 500 units per day before Statitrol sold its invention to Emerson Electric in 1980 and Sears’s retailers picked up full distribution of the 'now required in every home' smoke detector.

The first commercial smoke detectors came to market in 1969. Today they are installed in 93% of U.S. homes and 85% of UK homes. However it is estimated that any given time over 30% of these alarms do not work, as users remove the batteries, or forget to replace them.