Natural gas

At least weekly

Other gases, in particular synthesis gas and process gases such as refinery mixed gas, coke oven gas, blast-furnace gas, convertor gas

At least daily - using appropriate procedures at different parts of the day

Fuel oils (for example light, medium, heavy fuel oil, bitumen)

Every 20 000 tonnes of fuel and at least six times a year

Coal, coking coal, petroleum coke, peat

Every 20 000 tonnes of fuel/material and at least six times a year

Other fuels

Every 10 000 tonnes of fuel and at least four times a year

Untreated solid waste (pure fossil or mixed biomass/fossil)

Every 5 000 tonnes of waste and at least four times a year

Liquid waste, pre-treated solid waste

Every 10 000 tonnes of waste and at least four times a year

Carbonate minerals (including limestone and dolomite)

Every 50 000 tonnes of material and at least four times a year

Clays and shales