Special warning issued on exploding flashlights
May 1, 1998 4 minutes read
Special warning issued on exploding flashlights
Exploding flashlights represent an unusual but serious workplace hazard, according to a recent warning issued by the National Institute for Occupational Safety and Health (NIOSH).
Firefighters and other groups at riskNIOSH has received reports of incidents where flashlights have exploded while in use by firefighters, and safety officials caution that the same accidents could occur in other work environments.
In December 1992, a flashlight used in a firefighter training exercise exploded, slightly injuring one firefighter. In January 1995, a flashlight carried in a firefighter's pocket exploded, although he was not injured. Previous reports of exploding flashlights have appeared in the public safety literature.
The explosions are caused by the production of hydrogen gas. In the types of batteries most commonly used in flashlights - zinc/carbon batteries and alkaline batteries - hydrogen gas (H2) is produced naturally as a product of the corrosion of the zinc electrode in the aqueous electrolyte. Differences in batteries, including cell design and charge rate, affect the rate and volume of H2 generation. Excess hydrogen gas is more likely to be released if batteries are used incorrectly - if different types or brands of batteries are mixed, damaged batteries are used, old batteries are mixed with new batteries, or batteries are installed incorrectly.
Hydrogen accumulatingExcess hydrogen gas also may be produced by rechargeable batteries during recharging. If H2 accumulates within batteries or battery compartments without sufficient release, the buildup of pressure can cause the battery or compartment casing to rupture. Also H2 and oxygen (O2) mixtures are highly explosive, and if ignited by a spark or excessive heat can produce powerful explosions.
Many batteries or battery compartments are constructed to allow leakage and dissipation of H2. However, some battery compartments may be sealed tight against air and water by design. Some flashlights are constructed this way to enable their use by underwater divers and others who must have air- and water-tight equipment. Some manufacturers of equipment with air- and water-tight battery compartments have incorporated safeguards to prevent H2 accumulation.
For example, one-way relief valves may be incorporated in battery compartments to allow H2 to escape, or chemicals may be used to absorb or recombine H2. However, even these safeguards may not be sufficient if batteries are used incorrectly and excessive levels of H2 are produced.
The risk of explosion does not appear limited to one particular brand or type of flashlight because the explosion hazard is dependent on various conditions that allow the buildup of H2. However, the 1992 and 1995 explosions cited in this fact sheet involved one particular brand and model of flashlight: the Super SabreLite Submersible, Model 2000 series flashlight, manufactured by Pelican Products Inc. (2255 Jefferson St., Torrance, CA 90501). This flashlight features an air- and water-tight battery compartment and is used by underwater divers, military personnel, firefighters, hazardous materials workers, emergency response workers, and other public safety workers.
The Model 2000C incorporates both a pressure relief valve and a chemical catalyst to recombine H2. These precautions did not prevent the January 1995 explosion, which involved a Model 2000C. An examination by the Mine Safety and Health Administration (MSHA) found that use of different brands of batteries, with presumably different charge states, contributed to the 1995 explosion by causing the release of hydrogen gas at a rate that exceeded the venting capacity of the pressure relief valve.
An exploding flashlight has the potential to cause serious injury. In addition to injuries from the explosion itself, an exploding flashlight could touch off a larger explosion in a flammable atmosphere. The Super SabreLite Submersible Model 2000C is approved for use in flammable atmospheres by the MSHA, the Factory Mutual Research Corporation, and the Canadian Standards Association.
Follow NIOSH recommendationsNIOSH recommends these precautions to lower the risk of exploding flashlights:
· Read and follow manufacturers' recommendations for product use. The instructions often include information on how to reduce the risk.
· Do not mix batteries of different brands.
· Do not mix old and new batteries.
· Do not mix alkaline with nonalkaline batteries.
· Do not use damaged batteries.
· Ensure that proper polarity is observed when installing batteries.
· Before using an approved, battery-powered flashlight in flammable atmospheres, inspect it to ensure that the batteries are in good condition and that the proper batteries are installed correctly. Opening the battery compartment should allow any accumulated H2 to dissipate, but do not inspect the flashlight in a hazardous area or near an open flame.
Flashlights are not the only potential source of similar explosions. NIOSH cautions that the potential for explosion may exist in other battery-powered equipment.
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