Environmental Ranking Source Environmentally significant components 0* Firefighting agents Halons 0* Refrigerants CFC's 1 Vent gases CH4, H2S 2 Flare gases CO2, NOx, SO2, particulates 3 Exhaust gases COx, NOx, SOx, particulates, hydrocarbons 4 Fugitive gases Volatile organic compounds (VOC)

*Phased reduction of Halons and CFS's has already been agreed internationally under the Montreal Protocol of 1987 as amended in Copenhagen in 1992.

Table 4: Ranking of E&P atmospheric emissions.