1#Code figure Code figure Meaning 20 0 Air 31 1 Ozone 42 2 Water vapour 53 3 Methane 64 4 Carbon dioxide 75 5 Carbon monoxide 86 6 Nitrogen dioxide 97 7 Nitrous oxide 108 8 Nitrogen monoxide 119 9 Formaldehyde 1210 10 Sulphur dioxide 1311 11 Nitric acid 1412 12 All nitrogen oxides (NOy) expressed as nitrogen 1513 13 Peroxyacetyl nitrate 1614 14 Hydroxyl radical 1715 15 Ammonia 1816 16 Ammonium 1917 17 Radon 2018 18 Dimethyl sulphide 2119 19 Hexachlorocyclohexane 2220 20 Alpha hexachlorocyclohexane 2321 21 Elemental mercury 2422 22 Divalent mercury 2523 23 Hexachlorobiphenyl 2624 24 NOx expressed as nitrogen 2725 25 Non-methane volatile organic compounds expressed as carbon 2826 26 Anthropogenic non-methane volatile organic compounds expressed as carbon 2927 27 Biogenic non-methane volatile organic compounds expressed as carbon 30#28-39999 28-39999 Reserved 3140000 40000 Sulphate dry aerosol 3240001 40001 Black carbon dry aerosol 3340002 40002 Particulate organic matter dry aerosol 3440003 40003 Primary particulate organic matter dry aerosol 3540004 40004 Secondary particulate organic matter dry aerosol 3640005 40005 Sea salt dry aerosol 3740006 40006 Dust dry aerosol 3840007 40007 Mercury dry aerosol 3940008 40008 PM10 aerosol 4040009 40009 PM2P5 aerosol 4140010 40010 PM1 aerosol 4240011 40011 Nitrate dry aerosol 4340012 40012 Ammonium dry aerosol 4440013 40013 Water in ambient aerosol 45#40014-63999 40014-63999 Reserved 46#64000-65534 64000-65534 Reserved for local use 4765535 65535 Missing 48