A gas cooker is a flueless (Type A) appliance — its products of combustion go straight into the kitchen. So unlike a flued boiler, its ventilation isn't sized on kilowatts; it's sized on the volume of the room, because a bigger room dilutes the products more. This guide gives the figures and the rules around them. It's study material; only a Gas Safe registered engineer may carry out the work.

Standard. The figures come from BS 5440-2, Table 6 ("Minimum permanent opening free area for flueless appliances"), referenced by BS 6172. Manufacturer's instructions take precedence; confirm figures against the current edition.

The room-volume table

For a domestic oven, hotplate, grill (or any combination), the minimum permanent free area of ventilation is:

In every case the room must also have an openable window (or equivalent opening — an adjustable grille, louvre, hinged panel, etc.) direct to outside air. Work out room volume the obvious way: length × width × height.

Worked example. A kitchen 2.5 m × 1.5 m × 2.5 m = 9.4 m³. That falls in the 5–10 m³ band, so it needs a 50 cm² permanent vent plus an openable window to outside.

The door-to-outside exception

If the room has a door that opens directly to outside, no permanent vent opening is required (the door provides the air path). This is a common point that trips people up — a back door straight to the garden changes the answer.

The bedsit limit

A cooking appliance (unless it's just a single-burner hotplate or boiling ring) must not be installed in a bedsitting room of less than 20 m³. It's a safety floor for rooms that are also slept in, where products building up overnight would be especially dangerous.

Internal kitchens and air-tight homes

A kitchen with no opening to outside (an internal kitchen), or a very air-tight modern home, needs special attention — purge ventilation such as an extractor ducted outside, and reference to the Building Regulations and the relevant Gas Safe guidance. Don't assume the basic table covers these cases.

Get it wrong and it's classifiable. A cooker in a room that's too small, with too little ventilation or no openable window, is an unsafe situation under the GIUSP — typically At Risk, and two related faults can escalate. Ventilation here is a safety check, not a formality.
  1. Cooker = flueless; ventilation is sized on room volume, not kW.
  2. Under 5 m³ → 100 cm²; 5–10 m³ → 50 cm²; over 10 m³ → nil.
  3. An openable window (or equivalent) to outside is required in every case.
  4. Door direct to outside → no permanent vent needed.
  5. Bedsit: no cooker (beyond a single boiling ring) in a bedsit under 20 m³.
  6. Internal/air-tight kitchens need purge ventilation and Building Regs reference.
  7. Source figures from BS 5440-2 Table 6 / MIs; shortfalls are GIUSP issues.

10-Question Mock Test

Click an option to see whether you got it right. Explanations appear instantly — no submitting at the end.

Your score: 0 / 10
Question 1 of 10
A cooker's ventilation requirement is based on:
Question 2 of 10
Room volume under 5 m³ requires a permanent vent of:
Question 3 of 10
Room volume of 5 to 10 m³ requires a permanent vent of:
Question 4 of 10
Room volume over 10 m³ requires a permanent vent of:
Question 5 of 10
In addition to any permanent vent, every cooker room must have:
Question 6 of 10
A kitchen is 2.5 × 1.5 × 2.5 m (≈ 9.4 m³). The permanent vent required is:
Question 7 of 10
If the room has a door opening directly to outside:
Question 8 of 10
A cooker (more than a single boiling ring) must not go in a bedsitting room smaller than:
Question 9 of 10
An internal kitchen with no opening to outside needs:
Question 10 of 10
A cooker room with too little ventilation is generally:

100, 50, nil. Lock the cooker ventilation table in.

PlumbMate turns the figures examiners test into quick-recall practice mapped to the gas ACS tickets.

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