© 2003 Liberty Mutual Group – All Rights Reserved 1

Construction Safety Talks

Flammable Liquids

No. 61

How This Talk Applies To My

Crew:

Some Things To Know Before You Give Your Talk.

As a supervisor, you should let your crew know a fact that surprises a lot of people about flammable liquids: the vapor rising from the liquid is what burns, not the liquid itself.

When flammable vapor mixes with air and a flame or spark is present ignition occurs. The air-vapor mix has to be right but can vary quite a bit. For example, a mixture of anywhere from l% to 8% gasoline in air will explode. The range for acetylene is 2.2% to 80% by volume.

Whether the result of ignition is a fire or an explosion depends on the circumstances. In a closed space with the right mix, the burning is so violent that the sides of the building or the can are torn open. Here are a few examples:

• A mechanic decided to cut the end out of a 55 gallon drum that had been used for storing concrete curing compound. There was hardly any liquid but there was enough vapor and air in the drum to cause an explosion.

• Another explosion occurred while a tile setter was installing asphalt floor tile. The windows were closed because it was a cold day and when someone lit a cigarette there was enough vapor from the tile mastic, in the air, so that ignition occurred.

• A third explosion happened during spray painting of a storage space on a dredge.

Tell your crew that explosions can be prevented by:

• steam cleaning drums, tanks, or containers before a torch is used on them.

• providing enough ventilation to dilute flammable vapors.

• not permitting smoking and other sources of ignition where flammable liquids are stored or used.

© 2003 Liberty Mutual Group – All Rights Reserved 2

Try This For Show And Tell!

If your crew - or the jobsite - is equipped with a combustible gas meter, have a knowledgeable person demonstrate it and review the conditions under which it is to be used.

Questions You Can Use To Get Them Talking:

• Has anyone ever had an accident - or know of one - involving flammable liquids?

• What should you do if you suspect an area has a buildup of flammable vapors?

Attended By:

The illustrations, instructions and principles contained in the material are general in scope and, to the best of our knowledge, current at the time of publication. No attempt has been made to interpret any referenced codes, standards or regulations. Please refer to the appropriate code, standard or regulation making authority for interpretation or clarification.