Flammable & Explosive Hazards

Flammable & Explosive Hazards

Flammable limits are defined as the concentration range in which a flammable substance can produce a fire or explosion when an ignition source (such as a spark or open flame) is present. The concentration is generally expressed as percent fuel by volume.

For example, Methane (CH₄) has a Lower Flammable Limit (LFL) = 5.3%, and an Upper Flammable Limit (UFL) = 15.0%; if the air contains between 5.3% and 15% volume of air of methane (under normal atmospheric conditions), then a flammable environment exists.
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WARNING! Atmospheres that are rich in flammable gas (above the UFL) must be ventilated thoroughly, with powerfull blowers to completely bring the atmosphere down below the LFL.

Examples of LFL & UFL
Substance	Lower Flammable Limit (LFL)	Upper Flammable Limit (UFL)
Acetylene	2.5%	100%
Propane	2.1%	9.5%
Gasoline	1.4%	7.6%

OSHA/EPA Occupational Chemical Database & NIOSH Pocket Guide to Hazardous Chemicals