Combustible gas concentration conversion
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Everyone, I have a question I’d like to ask for your help. It is known that combustible gas detection alarms use methane as the reference gas. When testing gases containing toluene on-site, the reading shows 11% LEL (with the explosive limit for methane being 5%-15.4%). How can we calculate the concentration of toluene? Thank you all!
The last edit to this post was made by Wang Xiaoxiaobai Bai on 2016-3-8 at 15:27. The full English name of LEI is “Lower Explosion Limited”, which refers to the lower limit for explosion. When monitoring combustible gases in ambient air, the environmental hazard level of such gases is often given directly, expressed as a percentage of the concentration of the gas in the air relative to its lower explosive limit. This 11% LEL corresponds to 11% of the lower limit for methane explosion; assuming that the lower limit for methane explosion is 5%, then 5% equals 50,000 ppm. 1 ppm = 1 mg/m3, so this is basically the method for calculating concentration.
The one upstairs has gone off track, lol. What was asked is how to calculate the concentration of toluene. Methane is the most common combustible gas, and therefore it is also commonly used as the most common calibration gas ； To meet the application requirements for specialty gases, manufacturers generally provide a cross-coefficient table. For example, the cross-coefficient between toluene and methane is 2.1; this means that when using a combustible gas meter that has been calibrated with methane in a target gas (in this case, toluene), the reading obtained must be multiplied by this coefficient to determine the actual concentration of the target gas. In this case, the reading is 11% LEL; therefore, the actual concentration of toluene is 11% LEL * 2.1 = 23.1% LEL
You have to learn this*, I really don’t know.
How was this cross-data table obtained? How is it calculated specifically? Seeking guidance~~ Thank you~
Thanks for the help, it’s just a bit off from my question~~~:lol
I have a question: does that mean not just any \"combustible gas detector\" can be used to detect various types of gases? ? Mine is carbon monoxide; what is the cross-coefficient with propane? ? Thank you! ! !
Generally, no conversion is done; ordinary combustible gas detectors use the detected concentration as a reference, and then samples are sent for testing to determine the exact concentration. After all, on-site measurements are not reliable, so they can only serve as a reference value.
Generally, it is an empirical value obtained by manufacturers of gas detection instruments through repeated experiments on different types of combustible gases. For the specific calculation method, refer to what was described in the previous post
According to relevant standards, if the 11% LEL measurement refers to toluene, then the concentration of toluene is 5% multiplied by 11%.