For conversion between the two gas concentration units µg/m3 (microgram per cubic meter)|
and ppb (parts-per-billion).
Note that the Concentration Converter uses the temperature unit Celsius (°C). To convert from Fahrenheit or Kelvin you can use the calculator below. Type in the temperature value of your usual choice of unit, and click "Convert":
Please also note that the Concentration Converter takes the atmospheric pressure into account. This parameter is rarely measured during air pollution sampling, but the pressure actually do matter as it affect the volume of a gas. However, if this factor is unknown then use the normal atmospheric pressure at sea level: 1013 hPa (which equals 1013 mbar, 760 mm Hg, or 1 atmosphere).
The Concentration Converter can be used for any compound in air. You must know the molecular weight (Mw) of the compound in question. Mw of a number of important pollutants in the museum environment include:
The Concentration Converter is based on the equations:
C1 = ( C2 * Mw * 298 * P )/(24.45 * T * 1013 )
C2 = ( C1 * 24.45 * T * 1013 )/( Mw * 298 * P )
C1 = concentration in µg/m3
The equations are modified from ASTM (1991): Annual Book of Standards: Vol. 11.03, Atmospheric Analysis; Occupational Health and Safety, p. 54.
A calculator for atmospheric moisture (by Tim Padfield): http://www.conservationphysics.org/atmcalc/atmocalc.php
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IAQ in Museums and Archives, 2001. Updated 2016.