The Clean Air (Emission of Dark Smoke) (Exemption) Regulations 1969
Under section 1(1) of the Clean Air Act 1968 it is an offence to emit dark smoke from industrial or trade premises; but regulations may exempt, subject to conditions, the emission of dark smoke caused by the burning of any prescribed matter. These Regulations prescribe matters which are to be exempt and conditions applicable to each. The matters thus exempted include certain waste resulting from demolition or site clearance, explosives, ground and other surfaces, animal and poultry carcases, and containers used for pesticides and certain toxic substances.