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GAS DETECTOR ALARM SETTINGS

GAS

LOW

HIGH

TWA

STEL

O2 19.5% vol 23.5% vol N/A N/A
CO 35 ppma, b 70 ppmb 35 ppma  200 ppm
H2S 10 ppm 20 ppm 10 ppm 15 ppm
SO2 2.0 ppm 4.0 ppm 2.0 ppm 5.0 ppm
NO2 3.0 ppm 6.0 ppmc 3.0 ppm 5.0 ppm
Cl2 0.5 ppm 1.0 ppm 0.5 ppm 1.0 ppm
ClO2 0.1 ppm 0.2 ppm 0.1 ppm 0.3 ppm
CO2 0.5% vol 1.0% vol 0.5% vol 3.0% vol
PH3 0.3 ppm 0.6 ppm 0.3 ppm 1.0 ppm
NH3 25 ppm 50 ppm 25 ppm 35 ppm
HCN 5.0 ppm 10.0 ppm 4.0 ppm 4.0 ppm
NO 25 ppm 50 ppm 25 ppm 25 ppm
HCl 2.5 ppm 5.0 ppm 2.5 ppm 2.5 ppm
H2 50 ppm 100 ppm N/A N/A
CH4 1.0% vol 1.5% vol N/A N/A
LEL 10% LEL 20% LEL N/A N/A
PID 100 ppm 200 ppm N/A N/A

Note:
a. For CO, OSHA PEL is 50 ppm, Industrial Scientific uses the standard set in 1989 (35 ppm). All alarm set points are field adjustable over the full range of the sensor, exceptions: LEL/CH4 – 0 to 60% and 0 to 3.0% by vol CH4. Provided standards exist, all alarm settings are based on the following: Low alarms are based on OSHA PEL and/or NIOSH values. High alarms are based on 2 times OSHA PEL values.

b. MSHA CO limits are 50 ppm for a low alarm and 100 ppm for a high alarm.

c. MSHA NO2 limits are 5 ppm for a high alarm. 

Gas Detector Alarm Settings PDF