At what percentage of the lower explosive limit (LEL) must an area be considered a no entry zone during a natural gas emergency?

An area must be considered a no-entry zone during a natural gas emergency at 10% of the lower explosive limit (LEL). This threshold is established to ensure safety because concentrations of flammable gases, including natural gas, pose a significant risk of explosion and fire.

At 10% LEL, the risk of ignition increases considerably, necessitating that responders maintain a safe distance to avoid potential harm from any ignition source. By designating this level as a no-entry zone, the Minneapolis Fire Department prioritizes the safety of emergency personnel and the public, ensuring that all actions taken in response to the emergency minimize the risk of injury or further escalation of the incident.

Other percentages, while noticeable in terms of gas concentration, do not trigger the same level of caution as the 10% mark, where immediate intervention measures become critical.