Upper Explosive Limit (UEL) is what percentage?

Upper Explosive Limit (UEL) is what percentage?

• A. 15%
• B. 20%
• C. 25%
• D. 30%

Answer: (C)

The upper explosive limit is the highest concentration of a fuel in air that can still ignite and support combustion; beyond this point the mixture becomes too rich to burn because there isn't enough oxygen for the flame to propagate. For ammonia, the flammable range in air is commonly given as about 15% to roughly 25–28% by volume, and many training materials use 25% as the practical upper limit. So 25% represents that upper boundary in this context. The lower limit (about 15%) is the lower explosive limit, not the upper, and numbers like 20% or 30% don’t mark the upper boundary in the standard ammonia range.

The upper explosive limit is the highest concentration of a fuel in air that can still ignite and support combustion; beyond this point the mixture becomes too rich to burn because there isn't enough oxygen for the flame to propagate. For ammonia, the flammable range in air is commonly given as about 15% to roughly 25–28% by volume, and many training materials use 25% as the practical upper limit. So 25% represents that upper boundary in this context. The lower limit (about 15%) is the lower explosive limit, not the upper, and numbers like 20% or 30% don’t mark the upper boundary in the standard ammonia range.