# The Environmental Protection (Prescribed Processes and Substances) Regulations 1991, 

Extent: E+W+S

(a) Burning any fuel in a combustion appliance with a net rated thermal input of 50 megawatts or more;
(b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(c) burning any of the following in an appliance with a net rated thermal input of 3 megawatts or more otherwise than as a process which is related to a Part B process—
(i) waste oil;
(ii) recovered oil;
(iii) any fuel manufactured from, or comprising, any other waste.
For the purposes of paragraph (a) above, where—
(i)two or more boilers or furnaces with an aggregate net rated thermal input of 50 megawatts or more (disregarding any boiler or furnace with a net rated thermal input of less than 3 megawatts); or
(ii)two or more gas turbines or compression ignition engines with an aggregate net rated thermal input of 50 megawatts or more (disregarding any such turbine or engine with a net rated thermal input of less than 3 megawatts),
are operated by the same person at the same location those boilers or furnaces or, as the case may be, those turbines or engines, shall be treated as a single combustion appliance with a net rated thermal input of 50 megawatts or more.
Nothing in this Part of this Section applies to the burning of any fuel in a boiler, furnace or other appliance with a net rated thermal input of less than 3 megawatts.

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Source: https://www.legislation.gov.uk/uksi/1991/472/schedule/1/part/1/crossheading/section-13-combustion-processes-1 (the official version)
Page: https://openlegislation.uk/environmental-protection-prescribed-processes-and-substances-regulations-1991/schedule-1/part-1/crossheading-section-13-combustion-processes-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.