The flammable range is best described as:

• A. The percentage of gas or vapor concentration
• B. The temperature of ignition
• C. The concentration of oxygen in the environment
• D. The amount of heat produced during combustion

Answer: (A)

The flammable range refers to the percentage of gas or vapor concentration in the air, indicating the limits within which a combustible material can ignite and sustain combustion. This range is typically defined by two key concentrations: the lower explosive limit (LEL) and the upper explosive limit (UEL). When the concentration of the flammable material falls below the LEL or exceeds the UEL, combustion cannot occur. Understanding this concept is crucial in hazardous materials awareness because it helps first responders and safety personnel determine conditions under which a flammable substance could pose a risk of fire or explosion. The other choices describe important aspects of combustion but do not pertain specifically to the definition of the flammable range.