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ABOUT GAS
FAQ - Controllers
22. To what gas concentration should alarm setpoints be set?
This should be determined by reference to the TLV, STEL or LEL value of the substance being monitored.
For combustible gases in the range 0-100% of the Lower Explosive Limit (LEL), it is recommended that Alarm 1 be set to 25%LEL, Alarm 2 to 50%LEL and Alarm 3 to 75%LEL.
For toxic gases, refer to the TLV or STEL of the gas being monitored. However, we do not recommend that alarm setpoints be adjusted below 10% of full scale or above 90% of full scale.
Ultimately, the alarm setpoints should be selected by the safety officer responsible for the gas being monitored.