Filtering or purifying machinery and apparatus for gases
Catalytic converters or particulate filters, whether or not combined, for purifying or filtering exhaust gases from internal combustion engines
Intake air filters for internal combustion engines
Machinery and apparatus for filtering or purifying gases (excl. isotope separators and intake air filters for internal combustion engines, and catalytic converters and particulate filters for purifying or filtering exhaust gases from internal combustion engines)