Regulations: Gas Appliance Ventilation in Northern Ireland

A good air supply is essential to the safe working of a heat producing appliance.  The amount of air required will depend on the type of appliance, the input/output and the type of fuel it burns.  For your convenience, we have created a ventilation calculator for two popular gas appliance installations (see below) and outlined extracts from the following regulations:
  • Building Regulations (Northern Ireland), Technical Booklet L (October 2012).
  • For detailed guidance, refer to the full technical booklet available to download here.
Technical Booklet L: Combustion appliances and fuel storage systems
Regulation 70: Air supply

A combustion appliance shall be so installed as to receive a sufficient supply of air to ensure the safe and efficient operation of the combustion appliance and any connected flue.

Section 2: General provisions for combustion appliances
Permanently open ventilation of rooms

2.13: A permanently open air vent should be non-adjustable and be positioned where it is unlikely to become blocked.  It should be so installed that the building occupants are not provoked into sealing it against draughts or noise.  A permanently open air vent should not be located within a fireplace recess.

2.15: In a noisy area, it may be necessary to install proprietary noise attenuated air vents to limit the entry of noise into the building but these should not diminish the required air supply.

Section 4: Gas burning appliances with a rated heat input up to 70 kW (net)
Air supply for flued Decorative Fuel Effect (DFE) fires

4.5: A permanently open air vent should not be necessary for a DFE fire provided –
(a) the dwelling in which it is to be installed has an air permeability greater than 5.0 m³/hr/m².  See Appendix C;
(b) the appliance has a rated heat input not greater than 7 kW (net); and
(c) there is a flue gas clearance rate (without spilling) not greater than 70 m³/hour.

4.6: Where the provisions of paragraph 4.5 do not apply, any room or space intended to contain any other DFE fire should have a permanently open air vent as follows –
(a) for a DFE fire in a fireplace recess with a throat, the air vent equivalent area should be not less than 10000 mm²; or
(b) for a DFE fire in a fireplace with no throat, such as a fire under a canopy, the air vent free area should be sized in accordance with the provisions in Section 3, Table 3.1, as if the room were intended to contain a solid fuel fire.

Air supply for flued appliances other than Decorative Fuel Effect (DFE) Fires

4.7: This type of combustion appliance includes Inset Live Fuel Effect (ILFE) fires, radiant convector fires and boilers, in both room-sealed and open-flued variants.
4.8: The size of the free air supply to the combustion appliance should be in accordance with the provisions shown in Diagram 4.2.

Flueless appliances

4.10: The ventilation for a flueless gas appliance should be provided in accordance with Table 4.1.  For some flueless appliances, it may be
necessary to provide permanently open air vents and/or make provision for rapid ventilation as recommended in BS 5440: 2.

4.11: A room containing a gas point intended for use with a flueless appliance (such as a cooker, or space heater or water heater, with the gas point not adjacent to a flue) should have the ventilation provision calculated on the basis that an appliance with the largest rating consistent with Table 4.1 could be installed there.

Make a gas appliance calculation
House Year
Air Permeability:
Appliance Type:   
Appliance kW Input (net):   

General notes:

  • This calculation assumes the air vent will be in the same room as the appliance and positioned to access directly to the outside.
  • Rytons AirCore and AirLiner ventilation sets feature anti-draught systems to promote a comfortable environment in the room.  Achieve further draught protection by placing the air vent close to the appliance or at a high level close to the ceiling.
  • Rytons through-wall stove ventilators have equivalent area calculations as required by Technical Booklet L.
Rytons Gas Appliance Ventilation Range
Achieve compliant gas appliance ventilation with Rytons comprehensive range of ventilators.  We are always happy to assist you with ventilation calculations and product selection; call our technical sales office on 01536 511874 for advice.
Rytons Acoustic AirCore® and AirLiner® Ventilation Sets
Rytons Unsilenced AirCore® and AirLiner® Ventilation Sets
Rytons Floor

Rytons is proud to be a family run business and British manufacturer since 1972