Machinery and apparatus for filtering or purifying other gases
Machinery and apparatus for filtering or purifying gases other than air by a catalytic process (excl. those with stainless steel housing and with inlet and outlet tube bores with inside diameters < 1,3 cm, and catalytic converters for exhaust gases from internal combustion engines)
Machinery and apparatus for filtering or purifying gases other than air (excl. isotope separators, those using a catalytic process, those with stainless steel housing and with inlet and outlet tube bores with inside diameters < 1,3 cm, and particulate filters for exhaust gases from internal combustion engines)