The span of temperatures between the Upper Explosive Limit and the Lower Explosive Limit is called what?

• A. Combustion interval
• B. Flammable range
• C. Ignition span
• D. Burn spread

Answer: (B)

Flammable range. This is the interval between the lower explosive limit (the lean side) and the upper explosive limit (the rich side) where a fuel–air mixture can ignite and sustain combustion. If the mixture is too lean, there isn’t enough fuel; if it’s too rich, there isn’t enough oxygen. Within this range, an ignition source can start burning. The other terms described don’t capture this specific concentration band: they refer to different concepts like how fast something burns or how widely a flame can spread, not the flammability limits.