California Painting and Decorating Contractor (C-33) License Practice Exam

Lower explosive limit (LEL) is the minimum concentration of flammable gas or vapor in air that can ignite if an ignition source is present. Safety practice often uses a threshold of how far toward that limit the air has become to judge hazard. In this context, air is considered dangerous when the gas concentration reaches 20 percent of the LEL. At or above this level, the mixture is approaching the flammable range and requires immediate precautions such as ventilation, removing ignition sources, and monitoring. The other percentages represent different levels of hazard, but this item uses 20 percent of the LEL as the point at which air contamination is deemed dangerous.