The Road Vehicles (Construction and Use) Regulations 1986

13.  Every gas-fired appliance shall be—E+W+S

(a)so located as to be easily inspected and maintained,

(b)so located and either insulated or shielded that its use shall not cause or be likely to cause danger due to the presence of any flammable material,

(c)so constructed and located as not to impose undue stress on any pipe or fitting, and

(d)so fastened or located as not to work loose or move in relation to the vehicle.