Concentrations of chemicals in the air are usually measured as the mass of chemicals (milligrams, micrograms, nanograms or picograms) per volume of air (cubic meters or cubic feet). Concentrations can also be expressed as parts per million (ppm) or parts per billion (ppb) by using a conversion factor. This conversion factor is based on the molecular weight of the chemical and it is different for every chemical. The temperature of the atmosphere also has an influence on the calculation.
Formula: concentration (mg/m3) = 0.0409 x concentration (ppm) x molecular weight
For example: 100 ppm of NH3 (17.03 g/mol)
0.0409 x 100 ppm x 17.03 = 69.652
Gas | Output | Molecular Weight |
---|---|---|
Ammonia [NH3] | M = 17.03 g/mol | |
Carbon monoxide [CO] | M = 28.01 g/mol | |
Carbon dioxide [CO2] | M = 44.01 g/mol | |
Chlorine [Cl2] | M = 70.9 g/mol | |
Formaldehyde [CH2O] | M = 30.026 g/mol | |
Hydrogen [H2] | M = 2.02 g/mol | |
Methane [CH4] | M = 16.04 g/mol | |
Hydrogen Sulfide [H2S] | M = 34.08 g/mol | |
Nitrogen Dioxide [NO2] | M = 46.01 g/mol | |
Ozone [O3] | M = 48.00 g/mol | |
Perchloroethylene [C2Cl4] | M = 165.822 g/mol | |
Sulfur dioxide [SO2] | M = 64.06 g/mol | |
VOC | M = 78.9516 g/mol | |
Your input | M = g/mol |
Formula: concentration (ppm) = 24.45 x concentration (mg/m3) ÷ molecular weight
For example: 50 mg/m3 of NH3 (17.03 g/mol)
24.45 x 50 mg/m3 / 17.03 = 71.785ppm
Gas | Output | Molecular Weight |
---|---|---|
Ammonia [NH3] | M = 17.03 g/mol | |
Carbon monoxide [CO] | M = 28.01 g/mol | |
Carbon dioxide [CO2] | M = 44.01 g/mol | |
Chlorine [Cl2] | M = 70.9 g/mol | |
Formaldehyde [CH2O] | M = 30.026 g/mol | |
Hydrogen [H2] | M = 2.02 g/mol | |
Methane [CH4] | M = 16.04 g/mol | |
Hydrogen Sulfide [H2S] | M = 34.08 g/mol | |
Nitrogen Dioxide [NO2] | M = 46.01 g/mol | |
Ozone [O3] | M = 48.00 g/mol | |
Perchloroethylene [C2Cl4] | M = 165.822 g/mol | |
Sulfur dioxide [SO2] | M = 64.06 g/mol | |
VOC | M = 78.9516 g/mol | |
Your input | M = g/mol |
Source: Kansas State University
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