What impact does the LEL and UEL have on combustion?

The Lower Explosive Limit (LEL) and Upper Explosive Limit (UEL) are critical concepts in understanding combustion and fire safety. The LEL represents the lowest concentration of a gas or vapor in air that can ignite and support combustion, while the UEL represents the highest concentration at which combustion can occur. These limits define the safe operational range for combustible materials.

Understanding the LEL and UEL is essential for ensuring safety in environments where flammable gases or vapors are present. If the concentration of a combustible substance falls below the LEL, there isn’t enough fuel in the air to support combustion, and thus, the risk of ignition is eliminated. Conversely, if the concentration exceeds the UEL, there is too much fuel in relation to oxygen, which also prevents combustion.

This context demonstrates how knowing the LEL and UEL is vital for fire investigators and those working in hazardous environments to prevent fires and explosions, making option B the correct response. The other choices do not capture the essential function of LEL and UEL in defining safe combustion parameters, which is crucial for maintaining safety in flammable environments.