7241 Piped systems for flammable gases and gas mixtures for laboratory, industrial and commercial use (0) 7242 Piped systems for oxidizing gases for laboratory, industrial and commercial use (0) 7243 Piped systems for non-flammable gases and gas mixtures for laboratory, industrial and commercial use (0) 7244 Piped bactericidal, insecticidal, fungicidal, deodorizing and aromatic gas systems (0) 7245 Piped compressed air systems for laboratory, industrial and commercial use (0) 7246 Piped vacuum systems for laboratory, industrial and commercial use (0)