After ventilation, meters should check for natural gas presence below what LEL percentage?

The correct choice is 10% of the Lower Explosive Limit (LEL) for natural gas, which is significant for ensuring safety in environments where gas may be present. The LEL for natural gas typically sits around 5% by volume in air, meaning that at concentrations below this level, the gas is not considered hazardous for combustion.

Checking for gas presence at 10% of the LEL serves as an important precaution. At this level, there is still a low risk of explosion, but it highlights that gas is detectable and precautions should be taken. Monitoring at this threshold allows firefighters and first responders to act appropriately without jeopardizing safety.

This practice aligns with safety protocols, reinforcing the importance of vigilance during operations after ventilation is conducted.