What is the highest percentage of combustible gas detected by a detector, at which individuals should evacuate the area?

The correct answer is associated with a critical safety threshold established in many safety regulations and guidelines for combustible gases. At 10% of the Lower Flammable Limit (LFL), the concentration of combustible gas in the atmosphere poses a significant risk for ignition sources, such as sparks or open flames. This percentage serves as a precautionary measure; it provides a safety margin that indicates that the atmosphere is becoming unsafe to work in, effectively prompting an evacuation to ensure the safety of personnel.

The LFL is defined as the lowest concentration of a gas or vapor in air that can ignite and cause a fire. By establishing a threshold at 10% of the LFL, it allows for early detection and response before levels become dangerously high. This helps prevent accidents and protects the health and safety of individuals working in or around confined spaces where flammable gases may be present.

In practice, being alerted to gas levels at this threshold leads to necessary safety protocols, including evacuation from the area to minimize risk, thereby reinforcing the importance of regular monitoring and immediate action in hazardous environments.