Know the Flammable Basics

WHAT’S AT STAKE

Do you know the difference between flammable and combustible materials, or flash point, explosive limits and auto-ignition temperature?

WHAT THE DANGER

You need to understand these terms to work safely with flammable liquids — even if you only work occasionally with small quantities. For instance, if vapors are released from an open container or from a leak of flammable liquid, they can travel and leave a vapor trail which can catch fire.

EXAMPLE

Dave didn’t know that the vapors of a liquid labeled flammable burn or explode easily around an ignition source. He confused “flammable” with “combustible” (which means a liquid’s vapors will burn or explode when there is an ignition source, but not at temperatures lower than a certain point).After safety training, Dave realized that  if he knows a liquid’s flashpoint he can calculate the temperature range at which its vapors may burn or explode. He also now pays attention to auto-ignition — the temperature at which a substance will catch fire by itself.

HOW TO PROTECT YOURSELF

To understand container labels, material safety data sheets (MSDSs) and other hazard warnings, learn the following terms: Flammable and combustible liquids can burn. Their flashpoint determines the difference between them. Flashpoint is the lowest temperature at which the liquid gives off enough vapor to be ignited. The liquid doesn’t burn. Instead, its vapors burn when combined with oxygen.

• Flammable liquids have a flashpoint  below 37.8ºC (100ºF)
• Combustible liquids’ flashpoint is above that same temperature.

Flammable or explosive limits indicate the lowest and highest concentrations of vapors in the air which will burn or explode. These are referred to as the “lower flammable limit” (LFL) and “lower explosive limit” (LEL) or “upper flammable limit” (UFL) and “upper explosive limit” (UEL). When the vapor concentration is too low to burn, it’s said to be too “lean.” When too high, it’s too “rich” to burn. At its auto-ignition temperature, material burns without any source of ignition.  Flashback is not the same as flashpoint.  Vapors from flammable and combustible liquids which are heavier than air can settle in low areas. A vapor trail can spread far from the liquid itself. When the vapor ignites, the fire can flash back along this vapor trail to the liquid.

Test your knowledge

1. To understand hazard warnings, you may need to learn the meanings of some words.
True      False

2. “Flammable” is the same as “combustible.”
True       False

3. The lowest temperature at which a liquid gives off enough vapor to be ignited is its _____ .

 4. Auto-ignition temperature is the temperature  at which material burns without any source of ignition.
True       False

5. Flashback is the same as flashpoint.
True       False

What Would You do?
Terry paid a heavy price for learning about flashback. He spilled some gasoline from a gasoline can onto the floor of an automotive bay. Even though  the vapors had to drift far from the spill to find an ignition source, they did catch fire and the fire flashed back to the source. This caused the container of flammable liquid to explode. Terry survived the blast because he had immediately walked away to get cleaning cloths, but he was burned.

Answers on back of Log N Talk