Could I ask the view of the Technical Steering Group, manufacturers and ultimately Gas Safe, on the query outlined below, as I believe that this really is one of those grey areas.

In respect Gas Safety and catering ventilation systems, HSE Catering Information Sheet 23 & 10. These documents refer to the BESA formally (HVCA) document DW172. Section 4.3 of this document states “that when installing combination ovens, the overhang to the front of the canopy should be increased to 600mm, to cope with the steam or fumes, when the door is opened” My understanding of this is that DW172 have recommended this to contain the steam within the canopy as when the oven doors are opened the steam will spill outside of the canopy, this I have never regarded as a gas safety issue, as the products of combustion is to the rear of the appliance, and should be contained satisfactorily within the standard 300mm regulation for canopy overhang.

When we install a new canopy and the scheme includes a combi , we always allow for 600mm overhang however, when installing a combi to an existing canopy with a 300mm overhang, is the installation compliant with all regulations? If this is not this will have an impact on the replacement combi market.

I look forward to hearing from you on this matter.


  1. Whilst DW172 is accepted as the industry standard, it is not a regulation and therefore I am pretty sure that it will be the air quality CO2 readings (based on UP/19) that will determine the compliance of an installation in respect of ventilation, however, I have contacted Barrie Edgar at Gas Safe Register for his interpretation and will get back to you.I have heard back from Barrie who confirms that my initial reply is fundamentally correct, however, every installation should be subject to a risk assessment for that particular site to establish the implications of installing the combi. If it is a replacement for an old combi, it should be pretty straight forward, however, if it is an extra piece of kit, you need to establish that the ventilation is adequate to cope with it firstly from a gas point of view where DW172 air volumes should be used and secondly for the general atmosphere where a smoke test should indicate how much of the steam/hot air will dissipate around the kitchen. Assuming the air volumes are adequate, obviously the ideal solution is to fit a local extension to the canopy to bring it up to standard, however, if this is not possible, then assuming that the CO2 levels are under 2800ppm, you should record on your job sheet that the canopy is “not to current standard”.
  2. Follow up question from Member Many thanks for the clarification, the only thing I would add and, I don’t know if this has its own implications, Gas Safe have now done away with the clarification “Not to current standards”. 
  3. Follow up response from Technical Support  You are partly correct.  “Not to Current Standards” is no longer a reportable situation in the GIUSP as it does not necessarily relate to an unsafe situation, however, you can still record it on a job sheet. If you refer to our technical guidance document number 13 there is more detail.
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