The Vapors

Every work site has flammable and combustible liquids. A flammable liquid is much more volatile than a combustible one, meaning its vapors or fumes can ignite at temperatures below 100°F and some even lower than 32°F. Some common work site flammable liquids include gasoline, alcohols, lacquer thinners and some paint thinners. This means that, at normal room temperatures, flammable liquids can give off enough vapors to form burnable mixtures with air. On the other hand, a combustible liquid must reach temperatures higher than 100°F to release enough vapors or fumes to ignite. Combustible liquids common at a job site include fuel oil, kerosene and linseed oil. Both classes of liquids pose a very serious fire hazard.

Gasoline is probably the best known and most widely used of the flammable or combustible liquids. Many on a work site have used gasoline to clean off their hands, a tool or a piece of equipment. Some workers may have spilled a bit or finished a cigarette while filling a vehicle’s fuel tank or container. These events happen all the time, but remember that these behaviors are extremely dangerous. To help prove this point, this article presents some facts you need to know about gasoline:

  • Gasoline itself doesn’t burn; it’s the vapors from the gas that burn. Gasoline is very volatile when changing from a liquid to a vapor at low temperatures.
  • Gasoline vapors are denser than air, meaning these vapors will sink and collect at the lowest point. Effective air circulation may help disperse gasoline vapors.
  • An open flame is not necessary to ignite gas vapors; one spark can cause gasoline vapors to ignite.
  • Gasoline can be extremely irritating to the skin, in many cases causing a painful rash. This makes using gas as a cleaner a foolish idea. Always wash, with water, skin that has come in contact with gasoline. In addition, any clothing that comes in contact with gasoline must be changed immediately. By wearing clothes that have come into contact with even a small amount of the substance, you run the risk of becoming a human torch.

Refueling is a necessary part of the day at every work site. This makes it vital that the operations be conducted in a safe manner. The following are some things to remember when refueling, whether on the job or at home:

  • Keep either a carbon-dioxide or an ABC dry chemical extinguisher within 25 feet of any refueling operation. Having one closer would be ideal.
  • Keep your mind on the task at hand. If you are distracted while pouring gasoline, you run the risk of overfilling a container and spilling it.
  • Never smoke when refueling! Remember the vapors, not the liquid, ignite. That means a lit cigarette doesn’t have to be near the gasoline for it to catch fire. (Editor's note: Studies show lighted cigarettes don't ignite gasoline, because it's a smoldering ash. However, ELECTRICAL CONTRACTOR still recommends readers don't smoke when handling flammable and combustible materials.)
  • Clean up a spill immediately.
  • Never refuel near sparks or near work that’s being done with an open flame. A fire or explosion can result from the fumes coming in contact with one of these ignition sources.
  • Always be certain that both the fuel dispensing tank and the equipment being refueled are grounded. This will prevent a sparking issues.
  • Don’t overfill the tank; fill it only about 95 percent, especially on hot days. At high temperatures, gasoline will expand and eventually overflow.
  • If a vehicle might roll during refueling, chock the wheels. Before refueling, always shut the engine off and allow it to cool if necessary. When refueling is completed, be sure gasoline is drained from the hose, and check for any spills.

You should also properly store gasoline on the job site. Gasoline should always be stored in a Type I or II safety storage container. These containers control the gas vapors and provide an easy way to carry, dispense and store up to 5 gallons of gasoline. These containers must be able to withstand moderate mechanical shocks and will include vapor control; emergency venting; leak-tight, self-closing covers; and flame-arrestor-protected pour spouts. Most containers are made from rugged materials, such as stainless steel or polyethylene, and should have an independent testing laboratory listing or approval mark.

The main difference between Type I and II containers is the size of the pour spout. Type I has a wider spout for pouring gas into tanks or other large-mouth vessels while Type II’s smaller spout allows for more accurate pouring.

Having employees follow these safety suggestions during refueling can help to send them home safely.

About the Author

Diane Kelly

Safety Columnist

Diane Kelly is a safety and health specialist with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. She can be reached at 800.745.4818 or dkell...

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