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How do I convert ppm to mg/m3 and ppb to µg/m3?

Concentration (mg/m3 or μg/L) = Concentration (ppm) x

Molecular mass (g/mol)

Molar volume (L)

Concentration (μg/m3 or ng/L) = Concentration (ppb) x

Molecular mass (g/mol)

Molar volume (L)

For more information on calculating atmospheric concentrations, refer to Application Note 025.

Note that the ppm and ppb concentrations in these formulae are by volume, and the molar volume at 1 atm and 25°C is 24.45 L.

Conversion calculator

To convert units based on 25°C and 1 atm, fill in the ppm value (or the mg/m3 value) and the molecular mass, and click “Calculate”.


PPM Value


mg/m3 Value


Based on the Molecular mass of

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What is thermal desorption?

Thermal desorption (TD) is a versatile preconcentration technique for gas chromatography, which is used to analyse volatile and semi-volatile organic compounds from solids, liquids or gases.

Find out more by downloading our introductory e-book which explains more about the technique and it's place in the analytical laboratory


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