Setting of the alarm threshold for carbon disulfide gas detectors
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This post was last edited by Pseudo Xiao Bao on 2016-9-23 at 14:14. The alarm threshold for combustible gases is generally set at 20–25% LEL; therefore, the low alarm setting for combustible gas detectors is set at 25% LEL, while the high alarm setting is set at 50% LEL. The concentration of toxic gases is less than or equal to 100% of the maximum allowable concentration or the permissible concentration for short-term exposure. Carbon disulfide: Lower explosive limit (by volume): 1.0. Control measures for exposure/individual protection: Maximum allowable concentration: 10 mg/m3. Molecular weight: 76.14. Immediate harmful concentration IDLH: mg/m3; ppm: 500. 1 ppm = mg/m3 = 3.16. IDLH at 20°C: 1580. Olfactory threshold: 0.096 ppm. MAC (mg/m3): 10 (picograms). Is this setting for the toxic gas alarm values correct? Could the experts please provide the correct setting parameters? Thank you. Measurement range: 0–150 ppm. First-level alarm value: 3 ppm (approximately 10 mg/m3). Second-level alarm values: 15 ppm (47.4 mg/m3), or 30 ppm (95 mg/m3), or 50 ppm (or……)
Basis: Design Code for Detection and Alarm of Flammable and Toxic Gases in Petrochemical Enterprises (GB50493-2009), 5 Detection and Alarm Systems for Flammable and Toxic Gases, 5.3.1 Indicating and alarm devices shall have the following basic functions: 3 Measurement range for flammable gases: 0~100% of the lower explosive limit； 4 The measurement range for toxic gases should be 0~300% of the maximum allowable concentration, or 0~300% of the short-term allowable exposure concentration ； When the measurement range of the existing detectors cannot meet the above requirements, the measurement range for toxic gases can be 0~30% of the immediate harmful concentration ； 5.3.3 The alarm set values shall be determined in accordance with the following provisions: 1 The first-level alarm set value for combustible gases shall be less than or equal to 25% of the lower explosive limit ； 2 The secondary alarm setting value for combustible gases is less than or equal to 50% of the lower explosive limit ； 3 The alarm setting value for toxic gases should be less than or equal to 100% of the maximum allowable concentration/short-term allowable exposure concentration; when it is difficult to prepare standard gases for testing, the alarm setting value can be below 200% of the maximum allowable concentration/short-term allowable exposure concentration. When the measurement range of the existing detectors cannot meet the above requirements, the measurement range for toxic gases can be 0~30% of the immediate harmful concentration ； The secondary alarm setting for toxic gases shall not exceed 10% of the immediate lethal concentration.