Explosion Testing for dust, gases & vapours
© EHTL June 2015

Testing for flammability limits (LEL & UEL)

Lower and upper explosive limits for flammable gases and vapours

The test determines the lower and upper concentration limits of flammability of chemicals having sufficient vapour pressure to form flammable mixtures in air at atmospheric pressure at the test temperature. Above the upper explosible limit (sometimes called the upper flammable limit) the mixture of substance and air is too rich in fuel (deficient in oxygen) to burn. Below the lower explosible limit (sometimes called the lower flammable limit) the mixture of substance and air lacks sufficient fuel to burn. The test is based on central electrical ignition in a 12 litre flask with video recording to observe flame propagation. At the limit of flammability testing, a single frame of video may be sufficient to detect combustion flame. The applicable test standard is ASTM E681.
Explosion Testing
© EHTL June 2015

Testing for flammability

limits (LEL & UEL)

Lower and upper explosive

limits for flammable gases

and vapours

The test determines the lower and upper concentration limits of flammability of chemicals having sufficient vapour pressure to form flammable mixtures in air at atmospheric pressure at the test temperature. Above the upper explosible limit (sometimes called the upper flammable limit) the mixture of substance and air is too rich in fuel (deficient in oxygen) to burn. Below the lower explosible limit (sometimes called the lower flammable limit) the mixture of substance and air lacks sufficient fuel to burn. The test is based on central electrical ignition in a 12 litre flask with video recording to observe flame propagation. At the limit of flammability testing, a single frame of video may be sufficient to detect combustion flame. The applicable test standard is ASTM E681.