Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 21
Defined Terms: Room-Sealed Appliance
A room-sealed appliance has its combustion system isolated from the room, obtaining combustion air from outside the building or an uninhabited ventilated space, and venting products of combustion directly outside.
Room-sealed appliance – an appliance with a combustion system that is sealed from the room in which it is located, and which obtains air for combustion, from a ventilated uninhabited space within the building, or directly from the open air outside the building and vents the products of combustion directly to the open air outside the building. See Diagram 1.3(b), (d) and (f).
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet L - Combustion Appliances and Fuel Storage Systems.pdf