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FAQ 46 – Gas Boilers Not Subject to EPR/PPC Controls

How should emissions from gas boilers, not subject to EPR/PPC regimes, be considered for the purposes of LAQM Review and Assessments?

There are many gas boilers that are too small to require permission to operate under the Local Authority Integrated Pollution Prevention and Control (LA-IPPC) or Local Authority Pollution Prevention and Control (LAPPC) as required under The Environmental Permitting (England and Wales) Regulations 2016 (as amended) and the Pollution Prevention and Control (Scotland) Regulations 2012 (as amended). These boilers may be broadly categorised as “small” gas boilers.

Many small boilers/ furnaces are approved by local authorities under Section 4 of the Clean Air Act 1993. Section 14(2) of the Clean Air Act requires that an occupier of a building shall not knowingly cause or permit a furnace to be used in a building:

  • To burn pulverised fuel.
  • To burn any other solid matter at a rate of 45.4 kilograms or more an hour.
  • To burn gaseous matter at a rate equivalent to 366.4 kilowatts or more – unless the height of the chimney serving the furnace has been approved.

Approval may be granted by a local authority if they are satisfied that the height of the chimney will be sufficient to prevent gases from the chimney from becoming prejudicial to health or a nuisance.

Section 64(6) of the Clean Air Act (general interpretation) indicates that where a number of furnaces or boilers are served by one chimney then, for the purpose of the determination of chimney height as above, these will be treated as one furnace/boiler.

For conventional individual small gas boilers, room-sealed boiler systems and condensing boilers less than 1 MW with stack heights that have been approved by the local authority under the Clean Air Act having assessed the chimney height, no further assessment is required for Review and Assessment. But further consideration is required where there are:

  • Individual gas boilers with capacity > 366 kW not approved by the local authority using guidance in the third edition of the Chimney Heights Memorandum (HMSO, 1981), this may occur where under the Act the chimney height is deemed to be approved.
  • Multiple gas boiler installations with total capacity >366 kW.
  • Condensing boilers with capacity >1 MW.
  • Room-sealed boiler flue systems with capacity >366 kW not approved by the local authority using the Memorandum.
  • Fan-diluted emissions with capacity >366 kW.



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