Which explosive limit defines the maximum concentration of a flammable gas in air at which ignition can still occur?

Which explosive limit defines the maximum concentration of a flammable gas in air at which ignition can still occur?

• A. Upper Explosive Limit
• B. Lower Explosive Limit
• C. Upper Ignition Threshold
• D. Lower Ignition Threshold

Answer: (A)

Explosive limits define the range of fuel concentration in air that can sustain flame propagation when an ignition source is present. There are two ends: the lower explosive limit is the smallest concentration that can still burn, and the upper explosive limit is the largest concentration at which combustion can still occur. If the mixture is too lean, there isn’t enough fuel to ignite; if it’s too rich, there isn’t enough oxygen or the mixture won’t sustain flame. For many fuels, ignition can occur only when the concentration lies between these two limits. The maximum concentration at which ignition is still possible is the upper explosive limit, because it marks the point beyond which the mixture is too rich to ignite.

Explosive limits define the range of fuel concentration in air that can sustain flame propagation when an ignition source is present. There are two ends: the lower explosive limit is the smallest concentration that can still burn, and the upper explosive limit is the largest concentration at which combustion can still occur. If the mixture is too lean, there isn’t enough fuel to ignite; if it’s too rich, there isn’t enough oxygen or the mixture won’t sustain flame. For many fuels, ignition can occur only when the concentration lies between these two limits. The maximum concentration at which ignition is still possible is the upper explosive limit, because it marks the point beyond which the mixture is too rich to ignite.