Private Apartment, Orchard Place, Mayfair, London W1

This prestigious 8-storey apartment building is adjacent to Portman Square in Central London. The building incorporates a number of open-topped light wells. MDesign had designed a new interior for an apartment in the penultimate storey which featured a large air conditioning/heat pump unit venting to a 5m square light well. This unit was immediately below a bathroom window in the apartment above. The owner of the top apartment was concerned that the unit would be a fire risk.

I was asked to give an independent assessment of the fire risk. I pointed out that the building regulations official guidance (Approved Document B ‘Fire Safety’) does not recommend against the use of window- or wall-mounted AC units in external walls, and that this may be taken to imply that they are not regarded as a serious life safety hazard. Nonetheless, I examined the fire risk in the particular context. The AC unit was a heat pump which comprises a compressor and the associated electrical motor, a tank for storing the refrigerant and pipework operating at a pressure of 350psi. The refrigerant gas within the AC unit is held partly in vapour form and partly in liquid form in a pressurized tank. I considered a number of fire scenarios and, in particular, I examined what would happen if there should be a fire within the unit involving the release of a plume of vapour and the possible effects this might have on the neighbour above. My conclusion was that the fire risk was acceptable.

Client: MDesign London