The lowest concentration of a substance that will produce a fire or flash when an ignition source is present is known as what?

The lowest concentration of a substance that will produce a fire or flash when an ignition source is present is known as what?

• A. Lower explosive limit
• B. Upper explosive limit
• C. Flashpoint
• D. Autoignition temperature

Answer: (A)

The concept here is flammable limits, specifically the lower explosive limit. This is the minimum vapor concentration in air that can ignite or flash in the presence of an ignition source. Below this concentration, there isn’t enough vapor to sustain combustion; within the range between the lower and upper explosive limits, the mixture can ignite when sparked or lit; above the upper limit, the mixture is too rich to ignite. Different terms describe other ignition criteria: the flashpoint is the lowest temperature at which a liquid will emit enough vapor to form an ignitable mixture with air, while the autoignition temperature is the temperature at which a material will ignite on its own, without an ignition source.

The concept here is flammable limits, specifically the lower explosive limit. This is the minimum vapor concentration in air that can ignite or flash in the presence of an ignition source. Below this concentration, there isn’t enough vapor to sustain combustion; within the range between the lower and upper explosive limits, the mixture can ignite when sparked or lit; above the upper limit, the mixture is too rich to ignite.

Different terms describe other ignition criteria: the flashpoint is the lowest temperature at which a liquid will emit enough vapor to form an ignitable mixture with air, while the autoignition temperature is the temperature at which a material will ignite on its own, without an ignition source.