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Converting air pollutant concentrations

Converting air pollutant concentrations

The conversion equations depend on the temperature at which the conversion is wanted (usually about 20 to 25 degrees Celsius). At an ambient air pressure of 1 atmosphere (101.325 kPa), the general equation is:
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\mathrm{ppmv} = \mathrm{mg}/\mathrm{m}^3\cdot \frac{(0.08205\cdot T)}{M}
and for the reverse conversion:
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\mathrm{mg}/\mathrm{m}^3 = \mathrm{ppmv}\cdot \frac{M}{(0.08205\cdot T)}
where: 
ppmv= air pollutant concentration, in parts per million by volume
mg/m³= milligrams of pollutant per cubic meter of air
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T
= atmospheric temperature in kelvins = 273.15 + °C
0.08205= Universal Gas Law constant in atm·l/(mol·K)
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M
= molecular weight of the air pollutant (dimensionless)
Notes:
  • Pollution regulations in the United States typically reference their pollutant limits to an ambient temperature of 20 to 25 °C as noted above. In most other nations, the reference ambient temperature for pollutant limits may be 0 °C or other values.
  • 1 percent by volume = 10,000 ppmv (i.e., parts per million by volume).
  • atm = absolute atmospheric pressure in atmospheres
  • mol = gram mole

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