DFE fires: air vents and approved flue combinations

A decorative fuel effect (DFE) fire is designed for the look of a real fire, and a lot of room air goes up its flue. Approved Document J, Section 3, gives guidance for England and deals with its air supply separately from other gas fires.

Permanently open air vents

• In a fireplace recess with a throat: a permanently open air vent of at least 10,000 mm² (100 cm²) equivalent area (paragraph 3.11(a)).
• In a fireplace with no throat, such as under a canopy: the vent is sized using Section 2, as if the room were intended to contain a solid fuel fire (paragraph 3.11(b) and Table 1). The fixed 100 cm² does not apply.
• The exception: in a dwelling with an air permeability greater than 5.0 m³/h per m², a permanently open vent may not be needed for a DFE fire rated no more than 7 kW (net) whose flue gas clearance rate, without spilling, is no more than 70 m³/h (paragraph 3.12). Both limits apply together.
• Other flued fires, including inset live fuel effect and radiant convector models, use the applicable arrangement in Diagram 32 (paragraphs 3.13 and 3.14). Identify whether the actual model is open-flued or room-sealed: their combustion-air requirements differ.
• The 14 kW gross figure belongs to a different rule: the gas safety requirement for appliances in rooms used for sleeping.
• Where the vent goes: outside the fireplace recess and beyond the hearth, where draughts will not stir up dust or ash and are unlikely to cause discomfort. A vent within the recess needs specialist advice (paragraphs 1.10 and 1.11).

Which appliance, flue box and flue may be used

• A gas fire may go into a fireplace whose flue was built for solid fuel, provided it can be shown to be safe (paragraph 3.7).
• Use the appliance, flue box where needed and flue together as a tested combination covered by the manufacturer's installation instructions. Each part being suitable does not approve every combination of them.
• A satisfactory look up the chimney, a sweep's smoke test and the customer's choice of fire are all separate matters. None of them approves a combination the instructions do not list.

How many

Approved Document L 2021 limits the gas decorative fuel-effect fires installed in an existing dwelling to one per 100 m² of floor area, each meeting BS EN 509.