5.—(1) A person shall not install a gas fitting unless every part of it is of good construction and sound material, of adequate strength and size to secure safety and of a type appropriate for the gas with which it is to be used.
(2) Without prejudice to the generality of paragraph (1), a person shall not install in a building any pipe or pipe fitting for use in the supply of gas which is –
(a)made of lead or lead alloy; or
(b)made of a non-metallic substance unless it is –
(i)a pipe connected to a readily movable gas appliance designed for use without a flue; or
(ii)a pipe entering the building and that part of it within the building is placed inside a metallic sheath which is so constructed and installed as to prevent, so far as is reasonably practicable, the escape of gas into the building if the pipe should fail.
(3) A person shall not carry out any work in relation to a gas fitting or gas storage vessel otherwise than in accordance with appropriate standards and in such a way as to prevent danger to any person.