Ventilation for gas appliances

Natural gas and LPG require a certain amount of oxygen to burn correctly, but inadequate ventilation of gas appliances can create a serious health hazard.

Every cubic metre of natural gas needs 10 cubic metres of air for complete combustion. LPG requires 24 cubic metres of air. Too little air causes incomplete combustion which produces carbon monoxide.

To protect your health and safety, always make sure the people in your home understand how to use gas appliances safely.

Indoor gas appliances

Most indoor gas appliances use air within the room for the oxygen they need to burn gas. If the room doesn’t have enough ventilation to allow fresh air into the room, the amount of oxygen available will be depleted and other gases will build up.

Indoor gas appliances are designed and tested to operate safely in an indoor environment. They may be power flued, natural draught flued or unflued appliances.

Power flued appliances draw air from within a room and then use a fan or other powered system to push air and combustion products outside. Natural draught flued appliances use a chimney to draw air outside. Unflued appliances use air within a room and expel their combustion products into the same room.

Unflued and natural draught flue systems should not be installed in small rooms (eg bathrooms) or rooms used for sleeping, due to the risk of toxic levels of carbon monoxide building up. When flued systems are installed in other rooms, they must have permanent ventilation to outside.

Flued gas appliance safety

Flued gas appliances have fixed duct work, piping or chimneys to vent combustion products outside. Make sure the flue is not obstructed or blocked and that there are no holes in the flue before using the appliance.

Regularly inspect your gas appliance. Discolouration or stains on your walls or on the appliance, or moisture forming on the inside of your windows may be signs of a blocked flue.

If you think an appliance is faulty, contact a licensed gas fitter to inspect and service the appliance before you use it.

A room sealed gas instantaneous water heater has a flue that is partitioned to provide both air to the appliance while separately expelling the combustion gases outside. This is the only type of gas instantaneous water heater that can be installed in a bathroom or room with limited ventilation.

Unflued gas appliance safety

Unflued gas appliances have no direct way of venting combustion products outside, so it is vital that the room has adequate permanent ventilation to maintain safe air quality, prevent mould growth (due to moisture in the air), and to ensure the appliance can function properly.

By law, any room that has an unflued gas space heater installed must also have two permanent ventilation openings to outside the home – one at ceiling level and one at floor level. Each opening must have a minimum area of 1,000 square millimetres per megajoules per hour (MJ/h), based on the maximum gas consumption level of the heater. See below for restrictions on unflued gas space heaters approved for use in South Australia.

If you are using an unflued gas appliance indoors, never seal doors, windows, skylights or ventilation grilles while the appliance is running.

If you are purchasing an unflued gas appliance:

  • make sure it is safety tested and certified in Australia
  • be wary of buying gas space heaters online – safety standards for gas space heaters vary across Australia, so something from interstate or overseas may not comply with South Australian legislation or Australian safety standards
  • ensure you fully understand how much permanent ventilation is required for the appliance to be compliant and safe if you are purchasing it directly from a supplier
  • purchase from a reputable gas product seller, such as an energy retailer or gas heating specialist, who can help you choose the most suitable heater for your room.

Never use an unflued gas appliance in a bedroom, bathroom, caravan or marine craft (or any room used for sleeping).

Gas instantaneous water heaters must not be installed in a bathroom or room with limited ventilation unless they are a room sealed type.

Unflued gas space heaters approved for use in South Australia

There are restrictions on the types of unflued gas space heaters that can be installed in South Australian homes.

Before choosing and installing an unflued gas space heater, speak to a licensed gas fitter to ensure the heater is appropriate for the size and type of room, and there is adequate ventilation in the room it will be heating.

Portable unflued gas space heaters with a capacity of less than 18 MJ/h can be installed in South Australia, regardless of fuel type (ie LPG or natural gas). When the maximum gas consumption level of the unflued gas space heater is more than 18MJ/h, the system must have additional safety features. The table below lists systems consuming more than 18 MJ/h approved for use in South Australia.

Appliance (LP gas only)Model Capacity (MJ/h)

Galaxie (Rinnai)

REH 252


Avenger (Rinnai)



Avenger (Rinnai)



Outdoor gas appliances

Outdoor gas appliances, such as barbecues, camping stoves and patio heaters are designed for use in highly ventilated areas. When gas doesn’t burn properly, it produces toxic gases (eg carbon monoxide and nitrogen oxides) that are poisonous and can kill you. Using outdoor gas appliances indoors or in a confined space with limited ventilation is very dangerous, but using them correctly outdoors means the toxic gases will vent away quickly and safely.

If a gas appliance has been marked for outdoor use only, do not use it indoors or in partially-enclosed areas without adequate ventilation. Look for a warning label on the appliance or check the manufacturer’s instructions for more information.

BBQ warning labels

The Building Ideas television program, produced by the Master Builders Association of South Australia and featured on Channel 9, featured a segment on using gas appliances safely for outdoor entertaining.

If you intend to use an outdoor gas appliance in an area that is partially enclosed, such as a verandah, courtyard or gazebo, the area must have either:

  • no roof
  • at least two of the sides completely open with the open sides being at least half of the total wall area
  • one side is open and 30% of the remaining area is unrestricted, eg large, permanently open windows or vents.

For a non-rectangular area, follow the same principles and ensure at least half of the wall space around the structure is open for ventilation.

Examples of partially-enclosed areas that have adequate ventilation

No roof on structure

Diagram: with no roof on structure

Two sides open

Diagram:with two sides open

Two sides open

Diagram: two sides open

One side and 30% of remaining walls open and unrestricted

Diagram: one side and 30% of remaining walls open and unrestricted

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Page last updated 3 May 2019

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