These are used to analyse combustible gases or combustion by-products (burnt gases) in coke ovens, gas producers, blast furnaces, etc.,
in particular, for determining their content of carbon dioxide, carbon monoxide, oxygen, hydrogen, nitrogen or hydrocarbons. Electrical gas or smoke analysis apparatus are mainly for determining and measuring the content of the following gases : carbon dioxide, carbon monoxide and hydrogen, oxygen, hydrogen, sulphur dioxide, ammonia. The heading includes gas or smoke analysis apparatus for use in industrial processes (i.e., directly connected to furnaces, gas generators, etc.).
apparatus consisting merely of laboratory glassware falls in heading 70.17.