How to choose a detector for toxic gases such as H2S and SO2?
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It is required to measure H2S in the air; an alarm should be triggered when the concentration is 0.01 mg/m3 or higher； Measure SO2 in the air; an alarm is triggered when the concentration is 0.1 mg/m3 or higher. I would like to ask the experts: are there any toxic gas detectors capable of performing such precise measurements? After checking some information, it seems that the range of electrochemical measurements is around 0-10 ppm, with an accuracy of approximately 3%. So, can such small values as those required for measurement be detected?
0.01mg/m3？ 0.1mg/m3？ When you go to the scene, remember absolutely not to fart – otherwise they will call the police.
Can ordinary electrochemical toxic gas detectors measure such small amounts of H2S and SO2?
The range is 0–10 ppm, with a precision of 3%. At 10 ppm, 3% equals 0.3 ppm; thus the precision is 0.3 ppm. How is it possible to measure 0.01 ppm?
The measurement range for toxic gases should be 0–300% MAC or 0–300% PC-STEL； When the measurement range of the existing detectors cannot meet the above requirements, the measurement range for toxic gases can be 0–30% IDLH ； 6. Conversion between mass in mg/m3 and volume concentration in ppm: The concentration expressed as the mass of pollutants per cubic meter of air is called mass-volume concentration, with units of milligrams per cubic meter or grams per cubic meter. The conversion relationship to ppm is as follows: X = M.C/22.4; C = 22.4X/M. Here, X represents the concentration of the pollutant in milligrams per cubic meter ； C—Concentration value of pollutants expressed in ppm ； M—the molecular weight of the pollutant. From the above formula, the following relationship can be obtained: 1 ppm = M/22.4 (mg/m3) = 1000·M/22.4 ug/m3. The MAC value for hydrogen sulfide is 10 mg/m3, which is equivalent to 6.6 ppm; 0.01 mg/m3 corresponds to 0.066 ppm. Conventional hydrogen sulfide detectors have a measurement range of 0–100 ppm, so it’s impossible for them to detect such low concentrations. As for sulfur dioxide, you need to calculate it yourself. By the way, all of this information comes from GB50493. Where could you possibly use detectors capable of detecting such trace amounts of gases? ? Environmental monitoring? ?
If it is an offline instrument, it is not the responsibility of the instrumentation team.