Exception as to liability
39. No person shall be guilty of an offence by reason of contravention of regulation 3(2) or (6), 5(1), 7(3), 15, 16(2) or (3), 17(1), 27(5), 30 (insofar as it relates to the installation of a gas fire, other gas space heater or a gas water heater of more than 14 kilowatt gross heat input), 33(1), 35 or 36 of these Regulations in any case in which he can show that he took all reasonable steps to prevent that contravention.