At what oxygen level is the alarm in a gas detection meter typically set to go off?

In many gas detection meters, the alarm for low oxygen levels is typically set at 19.5%. This level is critical because it represents a threshold below which the atmosphere could become unsafe for human exposure. The normal concentration of oxygen in the atmosphere is approximately 21%. When levels drop to 19.5%, individuals can experience symptoms such as reduced stamina, impaired judgment, and other safety risks. Setting the alarm at this level allows for early intervention and evacuation if necessary, thereby enhancing safety in environments where oxygen displacement might occur, such as confined spaces. This is why 19.5% is the correct threshold for triggering an alarm in a gas detection meter, ensuring that personnel are alerted before the situation becomes hazardous.