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Appendix G: Quick Reference Conversion Tables

To convert ppb to µg/m3, multiply by:

Contaminant Symbol Molecular weight 0oC 10oC 15oC 20oC 25oC
Sulphur dioxide SO2 64 2.85 2.76 2.71 2.66 2.62
Nitric oxide NO 30 1.34 1.29 1.27 1.25 1.23
Nitrogen dioxide NO2 46 2.05 1.98 1.95 1.91 1.88
NOx (90:10 ratio) NOx 31.6 1.41 1.36 1.34 1.31 1.29
Ozone O3 48 2.14 2.07 2.03 2.00 1.96
Carbon monoxide CO 28 1.25 1.21 1.18 1.16 1.15
Carbon dioxide CO2 44 1.96 1.90 1.86 1.83 1.80
Hydrogen sulphide H2S 34 1.52 1.47 1.44 1.41 1.39
Methane CH4 16 0.714 0.690 0.677 0.666 0.654
*NMHC (light) C6 72 3.21 3.10 3.05 3.00 2.94
*NMHC (heavy) C12 144 6.42 6.21 6.09 6.00 5.89

* Non-methane hydrocarbon

To convert µg/m3 to ppb, multiply by:

Contaminant Symbol Molecular weight 0oC 10oC 15oC 20oC 25oC
Sulphur dioxide SO2 64 0.350 0.363 0.369 0.376 0.382
Nitric oxide NO 30 0.747 0773 0.788 0.801 0.813
Nitrogen dioxide NO2 46 0.487 0.504 0.514 0.523 0.532
NOx (90:10 ratio) NOx 31.6 0.710 0.734 0.748 0.761 0.775
Ozone O3 48 0.467 0.484 0.493 0.501 0.510
Carbon monoxide CO 28 0.801 0.829 0.844 0.859 0.870
Carbon dioxide CO2 44 0.510 0.527 0.537 0.546 0.555
Hydrogen sulphide H2S 34 0.659 0.682 0.700 0.707 0.719
Methane CH4 16 1.401 1.950 1.478 1.502 1.529
*NMHC (light) C6 72 0.311 0.322 0.328 0.334 0.340
*NMHC (heavy) C12 144 0.156 0.161 0.164 0.167 0.170

* Non-methane hydrocarbon