Indoor air quality

Most of us spend a large percentage of our lives indoors, so it is worth thinking about air quality in our homes. Poor indoor air quality may produce a range of health effects, from mild and generally non-specific symptoms such as headaches, tiredness or lethargy, to more severe effects such as sensitisation to allergens and aggravation of asthma and allergic responses. Poor indoor air quality in your home may exacerbate pre-existing conditions or cause new health issues.

Whether a source of air pollutants causes an indoor air quality problem or not depends on:

• the type of air pollutant
• the amount and rate at which it is released from its source
• the degree of ventilation available in the home to remove it from indoors
• the leakiness of your home, if the pollution source is outside
• the sensitivity of the person and any pre-existing conditions.

Some groups of people in the community are more vulnerable to pollutants than others, or are likely to spend more time indoors than the general population. These people include:

• the very young
• the very old
• those with pre-existing respiratory or cardiovascular disease
• those who are sensitised to specific substances.

Generally, the greater the amount of pollutant (exposure), the greater the health impact. The duration of exposure is also important – if low-level exposure occurs over a long period of time (perhaps many years) the total dose may be large.

What you do in the home can make a significant difference to the health of the indoor environment. For example, smoking, and poor cleaning procedures can add to air pollutants.

Photo: Thompson Sustainable Homes

Indoor air pollutants

There are many different types of indoor airborne pollutants. Some types of pollutants and allergens are more common than others, and some are more hazardous than others. The following section describes various air pollutants that may be found in the home, from more to less common.

Dander and dust mites

Pet dander and dust mites can aggravate hay fever, asthma, nasal inflammation and eczema. Dander and dust mites are generally present in soft furnishings, including carpet, bedding and furniture.

To reduce the amount of dander and dust mites in your home, install hard flooring or vacuum often with a high-quality vacuum cleaner. Wash bedding and other soft furnishings frequently, and replace pillows and cushions regularly.

Mould

Mould produces tiny particles called spores that become airborne. When inhaled by people who are sensitive or allergic to them, they can cause irritation of the nose, eyes and skin, aggravate asthma and other respiratory diseases, and occasionally cause more severe health issues. Mould can grow indoors in damp areas, including bathrooms, damp rooms, windowsills, indoor plants and poorly ventilated areas. Strategies to prevent mould include:

• install insulation and building membranes correctly to reduce condensation risk
• install the correct waterproofing to bathrooms and wet areas
• fix rising damp in existing buildings and improve subfloor ventilation
• fix sources of moisture such as leaks in plumbing or roofing
• reduce humidity inside the home by venting sources of moisture to the outside (for example, use exhaust fans in kitchens and bathrooms)
• remove condensation and mould as soon as possible.

Smoke and combustion products

Combustion products include smoke (small soot particles), ash and gases (including nitrogen dioxide and carbon monoxide) that can get inside your home from fireplaces and heaters burning wood, coal, gas or kerosene, gas cooking appliances, fumes from cooking (especially frying), tobacco smoking, bushfires, exhaust from cars in adjoining garages, and hobbies such as welding and soldering.

Combustion particles are so small they behave almost like a gas — they can enter or leave a home very easily. When you breathe them in, they travel into the deepest parts of the lungs. They can cause eye, nose and throat irritation; aggravation of asthma; chronic respiratory disease; and lung cancer.

To maintain good air quality when you have combustion sources inside the home:

• ensure plenty of fresh outdoor air is coming into the room
• vent pollutants to the outdoors (via a flue, chimney, exhaust fan or range hood)
• keep flues and chimneys clean, and make sure any permanent ventilation openings are not blocked
• service heating or cooking appliances regularly to ensure they are working properly and are not leaking gases into your home, and never use an appliance if it is damaged or not working properly
• always follow the appliance manufacturer’s instructions — seek advice from the manufacturer, supplier or your gasfitter or plumber if you have any concerns
• ensure doors connecting garages to the house are tightly sealed and minimise running time for vehicle engines in garages connected to the home
• do not use barbeques or camp stoves indoors and do not use a gas oven or gas cooker to heat a room
• avoid smoking inside or near the home – smoking on balconies and terraces may reduce but will not eliminate environmental tobacco smoke in the home
• ensure your home is designed to allow controllable ventilation and can be well sealed when required, to avoid pollutants from outdoor combustion sources (for example, bushfires) entering the home.

Volatile organic compounds

Volatile organic compounds (VOCs) are chemicals containing carbon that evaporate into the atmosphere at room temperature. Formaldehyde is one of the most common VOCs. VOCs often have an odour and are present in a wide range of household products, construction materials, and new furnishings. Household products that contain VOCs include paints, varnishes, adhesives, synthetic fabrics, cleaning agents, scents, and sprays. VOCs can also result from personal activities, such as smoking or vaping.

When used in building products or other indoor items, VOCs slowly make their way to the surface of the material and ‘off-gas’ into the surrounding air. Most off-gassing occurs when products are new or freshly installed, after which it lessens dramatically over time. Off-gassing increases with higher temperatures.

VOCs can cause eye, nose and throat irritation, and headaches.

There are 2 main strategies to reduce VOC exposure in the home:

• Stop or reduce the use of products that contain VOCs.
  • Look for products certified by Good Environmental Choice Australia, or rated E1 (good) or E0 (best) by the European Emission Standards.
  • Look for building products that are pre-dried in the factory or are ‘quick-drying’.
  • Use surface-coating products that are water based or classed as containing zero or low levels of VOCs.
  • Seek advice from the supplier or manufacturer, particularly if the information displayed on the container is not clear — ask for the product’s material safety data sheet (MSDS).
  • Check eco-comparison websites; these can help you select building materials and products with low or zero VOC content refer to References and additional reading for more information.
• When adding new furnishings or resurfacing walls and floors, ensure rooms are fully ventilated until the odour reduces considerably or disappears. Open doors and windows whenever practicable. Air fresheners, cleaning sprays, polishes, spray deodorants, and other toiletries are major sources of VOCs and should not be used excessively in nonventilated areas.

Lead

Lead is a concern when small particles or fumes are swallowed or inhaled. Absorption of lead is associated with poor childhood intellectual development, and its use in paints and other materials has been banned. Many older building and household products contain lead, but newer products no longer do. The highest risks are found in pre-1970s homes. Items such as old paint, flashing, old plastic pipe and fittings, electrical cabling and glazed pottery can contain variable amounts of lead.

Contact with lead can arise from home renovation activities, particularly when stripping old paint, through some hobbies (for example, lead-lighting, making fish sinkers, or pottery glazing) or coming into contact with contaminated soil.

Take care when renovating. Avoid sanding, abrasive blasting or burning paint containing lead, for example on window frames. Do not burn old painted wood in fireplaces or in barbeques. Refer to the Lead Education and Abatement Design Group (LEAD) website for further information.

Asbestos

Asbestos was used widely in the construction, car, and textile industries because of its strength and ability to resist fire and acid. It is no longer allowed to be used in building products for the home because of the risk of various illnesses including mesothelioma and lung cancer. As a general rule, asbestos-containing products are highly likely to be present in a house built before the mid-1980s, likely to be present in a house built between 1985 and 1990, and unlikely to be in a house built after 1990.

Asbestos-containing products were rarely labelled. Products like cement sheets, roofing sheets, some textured paints, vinyl floor tiles, pipe lagging and fire-resistant boards, and blankets used in the home before the mid-1980s may contain asbestos. Asbestos-containing products can be ‘friable’ (loose and easily crumbled) or ‘non-friable’ (made with a bonding compound like cement).

Friable asbestos-containing products are less common in homes, but may exist in some homes built before 1990. They include pipe lagging and some types of insulation, and are dangerous because the fibres can easily become airborne when disturbed.

Non-friable asbestos-containing products include asbestos cement sheeting and vinyl floor tiles. The asbestos particles in non-friable products are tightly bound and so these products are generally not a health risk unless cut, broken or drilled into, in which case they will produce fibres or dust. Asbestos fibres may then be released into the air, inhaled and damage lung tissue.

Always seek professional advice about managing asbestos in your home. Accurate identification can be difficult, and immediate removal is often not the best option.

Airtightness and healthy interiors

In recent years there have been widespread improvements to airtightness and insulation levels in Australian housing. These improvements have resulted in better thermal comfort and energy efficiency, but without an understanding of the correct building principles there can be unintended consequences for indoor air quality. An airtight house with inadequate ventilation may lead to condensation and mould, high internal levels of carbon dioxide, and increased exposure to other internal pollutants. The build-up of gases, toxins and pollutants resulting from increased airtightness can trigger respiratory health issues.

To combat these problems, provide reliable ventilation (for example, mechanical ventilation with heat recovery) and avoid potential sources of pollution. Pay particular attention to building membranes and insulation, ensuring they are installed correctly for your climate. Refer to Ventilation and air tightness for more information.

Assessing your health

If you are concerned that indoor air quality may be affecting your health, consider the following:

• Do you notice any change in your health before and after a particular change in the home environment?
• Is there any change in your health after particular activities, like dusting or cleaning?
• Do your health problems occur at the same time each year?
• Do your health problems get better if you and your family are away from home for any extended periods, such as holidays?

Consult your doctor if you are concerned about any changes to your health.

Photo: Dick Clarke

There are 5 key aspects to achieving better indoor air quality:

• Prevent — Do not allow potentially harmful products into the home.
• Eliminate — Identify the source of air problems and wherever possible eliminate them through better product selection and design.
• Ventilate — Ventilate the home to remove pollutants before they accumulate to levels that can pose health and comfort problems.
• Separate — Separate problem materials from occupants by using air barriers or sealers such as coatings.
• Absorb — Indoor plants can be used to improve the quality of the indoor environment, as well as to add beauty.

Planning and design

If you are building a new home, thinking about air quality during the planning and design phases will help to achieve good air quality in your new home, without the need for expensive refits.

If you are renovating an existing home, consider what effects renovations may have on air quality. The materials used in some old homes, as well as the activities associated with renovation, can increase the health risks for renovators and anyone else in the home during the work. Assess the risks, including signs of dampness, and manage them through safe work practices and clean-up. It is a good idea to get a building inspection report done by a professional.

The site

You should consider what substances are likely to be in and around the site for your home.

The land on which you intend to build (or have built) may have chemical residues from previous industrial or agricultural processes. Talk to local long-term residents about the land’s former use. Visit the planning section of your local government. Get advice about legal searches that might show how the land was used.

Check how emissions from existing or future industries might affect your home. The closeness of a main road, bus depot, airport, orchard, or industrial plant can affect the amount of airborne pollutants entering your home. Check with your local council about future land use in your area. The National Pollutant Inventory is a database of national information on pollutant emissions and their sources.

If you have hay fever or asthma, find out whether local plant species will cause problems when they flower. Ask a local plant specialist about the main local vegetation types within a kilometre of your new home.

You should also consider how air will move around the site. Local topography, proximity of trees and nearness to water all influence air temperatures and wind patterns around your home. A home on top of an exposed hill will be affected differently to the same home in a deep valley or on an urban block with houses nearby. Design to enhance natural ventilation and shelter in a way that takes account of your home’s specific location refer to Choosing and using a site for more information.

Ventilation and airtightness

Strike a balance between the need to introduce fresh air, maintain comfortable room temperatures and conserve energy – the ideal design strategy will depend on your climate.

Good design and orientation can encourage breezes and convection currents to draw stale air out and fresher air into your home. If windows are closed for security or noise reasons, fixed wall vents can be installed to ensure adequate ventilation. You can also consider installing security products that allow you to feel secure but also allow you to regulate the air flow between indoors and out. Mechanical ventilation with heat recovery is a way to ensure reliable ventilation and maintain high levels of energy efficiency.

Ducted air systems may heat or cool recirculated indoor air but fail to introduce fresh air from outdoors or remove pollutants. Evaporative cooling systems increase indoor humidity and may increase levels of mould or dust mites. Make sure all units are regularly maintained. Regular cleaning of the ducts and the air filters in ducted systems and reverse cycle air-conditioners is recommended, for example at the beginning of the heating or cooling season.

Choose a garage that stands apart from your home. If it is attached, make sure the linking door is well fitted and able to be securely sealed against leaks. The exhaust from conventional petrol and diesel engines contains many pollutants, including millions of very fine particles and a variety of toxic gases. Such engines should not be run in confined spaces (like a garage) for more than a few seconds, unless there is very good ventilation. Do not allow contaminated air from the garage to circulate through your home.

Air-conditioning can help to filter particles from indoor air, but be sure to switch your air conditioner to ‘recycle’ or ‘recirculate’ during smoky conditions. Testing by Australian consumer advocacy group Choice suggests that air purifiers can filter smoke particles well and make significant improvements to indoor air quality.

Interiors

Eco-comparison sites can provide information to help you choose products and materials with no or minimal adverse health impacts refer to References and additional reading for more information.

Joinery, fixtures and furniture

If you are installing joinery (for example, kitchen or bathroom cabinets, built-in cupboards) or buying new furniture or fixtures, be aware that most modern furniture is made wholly or partly from plywood, particleboard or medium-density fibreboard (MDF). The resins in these products can off-gas formaldehyde for many years. Australian manufacturers produce low-emission products: they are marked low formaldehyde emission LFE (E1) or LFE (E0) and their emissions are certified through product quality assurance programs. Some imported products may have high emission levels. Check the origin and emission class with your retailer, or contact the Australian Wood Panels Association.

Many soft furnishings contain foams or other synthetics. These can release various unhealthy gases over time. Some manufacturers are working to reduce off-gassing. Ask suppliers for details about the chemicals used in the product, particularly VOCs, and their advice on possible health effects. Try to find products with low-emission labels.

Painting

The following advice applies to both interior and exterior painting, but minimising VOCs is particularly important when you are painting indoors.

Choose paints with zero or low levels of VOCs. Ventilate the home well both during and after painting indoors.

Most of the potential health risks occur when renovating older homes. During the preparation stage, rubbing existing paint with an abrasive, such as sandpaper, creates a lot of fine particles. This is a potential health risk, both when the particles are in the air (where they can be inhaled) and when they settle on a surface (where children or pets may swallow them). Contractors know how to capture the dust before it travels any distance through or into your home and should take care in cleaning up residues. If you are doing the work yourself, ensure you use a well-fitted face mask and clean up well after the work is finished.

Take particular care if you have an older home. Lead paint is most likely to be found in homes built before 1970. Paints containing up to 50% lead were commonly used on the inside and outside of houses built before 1950. Up to the late 1960s paint with more than 1% lead was still being used. Regulations have reduced the levels of lead in paint to 0.1%. Commercial home test kits are available from some hardware stores to discover if you have lead paint. For more reliable results, use the services of an analytical laboratory. If you do find lead paint, phone your state or territory public health unit for advice.

Floor coverings

Consider whether you will have carpets or hard flooring in your home.

Trapped dust and microbiological pollutants can be a problem if they are released from carpets into the air, or may be a direct problem for crawling babies and young children playing on carpets. Design and furnish your home with easy-to-clean surfaces and fabrics.

If new carpets are fixed with adhesives, these may contain VOCs. Underlay can also be a source. Ask for carpets promoted by manufacturers as low emission products. Make sure your supplier unrolls the carpet in a well-ventilated area and lets it air for several days before it is delivered and installed.

Smooth floor surfaces such as ceramic tiles, vinyl linoleum or polished wood can be easier to clean. Before specifying such products, check whether there are likely to be any VOCs present, either in the product itself or in other products used to lay it (for example, adhesives) or to seal the floor covering (for example, varnishes and paints) and for maintenance products such as cleaning fluids and polishes.

Architect: Studio203. Photo: John Gollings

Heating

If you are thinking about using gas for heating, buy appliances that vent their combustion products to the outside. Unvented mobile gas heaters may pose a health risk and have been associated with more frequent respiratory symptoms. If the use of unvented heaters is unavoidable, buy only low-NOx (nitrous oxide) appliances, and do not operate them in confined spaces for long periods of time. Ventilate the heated area with fixed wall vents (compulsory in some states). Ensure regular maintenance and servicing by a licensed gasfitter. Older heaters (pre-1990) are more likely to produce higher NOx values than new heaters. Consider replacing your old model with a new, flued (vented) model. Do not use unflued gas heaters in draught-proofed homes.

If you are thinking about using wood for heating, remember that poorly installed or badly maintained wood-burning heaters and stoves can be a major source of fine combustion particles and gases from leaks and from opening of the door for refuelling. Before installing a wood-burning heater or stove, check which options are permitted by your local government. Compare safety and efficiency claims of competing manufacturers. Ensure the flue or vent is properly designed and installed, regularly maintained and used in accordance with the manufacturer’s instructions.

Refer to Heating and cooling for more information on heating options.

Construction

Damp proofing and condensation management

In brick homes, if a damp-proof course has not been fitted or has been broken, moisture may migrate from the ground into the wall. If building membranes and insulation have not been installed correctly for your climate, condensation can result. High and prolonged periods of humidity can increase the moisture within the building. Avoid mould growth by lessening moisture levels in your home. Refer to Ventilation and air tightness for more information.

Termite protection

Termites are part of Australia’s ecology, and termite barriers are required to protect buildings from termite damage. These can be physical barriers, which are nontoxic and long-lasting, or chemical barriers that must be periodically reapplied. Specially designed physical barriers, such as mesh or crushed rock, reduce the need for extensive and repeated chemical treatment and are preferable from an environmental perspective. In the past, environmentally persistent organochlorines were used in chemical barriers but these are now banned due to health and environmental concerns. The replacement — organophosphates — pose less of an ecological hazard and have less potential for long-term health risks.

Photo: Ben Wrigley (© Light House Architecture and Science)

Maintenance

Paying attention to day-to-day upkeep and cleaning can help to maintain good indoor air quality.

Cleaning

Carried in on footwear, pollutants can enter your home and become part of the breathable dust load. Doormats can reduce the amount of material brought into your home. Clean your mats regularly or establish a shoe-free house by leaving shoes outside and offering guests a pair of slippers.

Poorly cleaned and old carpets with flattened fibres become reservoirs for dust and microbiological pollutants. Clean carpets regularly to minimise health risks. Invest in a vacuum cleaner with high filter efficiency (HEPA filters) and mechanical pile agitation. If your health or that of your family seems to suffer after floors have been vacuumed, consider a central vacuum system which expels air outdoors. If you are particularly sensitive to allergens found in dust, avoid vacuum cleaning or wear a face mask during vacuuming and for a short period afterwards. Smooth flooring should be cleared of dust before wet mopping so that the water does not simply spread the dust.

Consider having your carpets professionally cleaned every so often. Seek professional advice about the best way to clean your carpet — methods will vary depending on the type of carpet, its ‘backing’ and underlay, and the level of traffic and type of use.

A well-sited kitchen exhaust fan or range hood that vents to the outside may remove many of the particles and gases that arise when cooking on gas stoves, but fat droplets settle within the vent. These deposits build up over time and can become both a fire hazard and a home for fungi and bacteria. Clean exhaust fans and range hoods regularly as per the manufacturer’s instructions.

Avoid cleaners with fragrance because they will include VOCs. Most liquid cleaning agents, many personal hygiene products, air fresheners, and perfumed toiletries contain VOCs. Some people’s health rapidly deteriorates after smelling or coming into contact with these types of product, even for just a few seconds.

Mould

Depending on your home’s original design or the impact of recent renovations, there may not be enough ‘air changes’ to quickly remove moisture. The kitchen, laundry, and bathrooms should have exhaust fans to vent moist air to the outside. Ask your fan supplier about energy-efficient models. In the absence of exhaust fans, and where it is safe to do so, open kitchen and bathroom windows to ‘flush’ the air after cooking, washing clothes, and bathing.

If moisture builds up inside a wall cavity or in the insulation layer, harmful mould may grow inside. Refer to Condensation for advice on reducing the risk of condensation forming inside structures.

Pests

Cockroaches seek tight spaces to squeeze into. Poorly fitted kitchens provide ideal cracks and crevices for cockroaches, along with food and water. Poorly sealed holes for pipes may also allow mice and other pests to enter your home. Plug all gaps between kitchen units, walls and floor. Ask your local hardware supplier about the types of nontoxic gap sealants available.

If you have a compost heap, it should be located well away from living areas and will need regular maintenance. Unless the heap is managed correctly, not only will it attract unwanted pests, such as rats, mice and cockroaches, but it may also increase the numbers of fungal spores in the air close to your home. Most gardening books and nurseries provide good information on how best to look after your compost heap.

• Eco-comparison websites
  –    Australian National Life Cycle Inventory Database.
  –    Building Products Information Rating.
  –    Ecospecifier Global
  –    Environmental Product Declaration Australasia.
  –    Global GreenTag.
  –    Good Environmental Choice Australia.
• Asbestos Safety and Eradication Agency.
• Asthma Australia.
• Australasian Society of Clinical Immunology and Allergy.
• Australian Government Department of Agriculture, Water and the Environment, Lead in house paint.
• Australian Institute of Architects Practice Notes, Indoor environment quality.
• D’Alessio V (2002). Allergy free home: a practical guide to creating a healthy environment. New Holland, Sydney.
• Environmental Health Standing Committee (enHealth) (2013). Asbestos: A guide for householders and the general public, Australian Health Protection Principal Committee, Canberra.
• Lead Education and Abatement Design Group.
• National Research Council (1981). Indoor air pollutants. National Academy Press, Washington DC.
• Spengler J, McCarthy J and Samet J (eds) (2001). Indoor air quality handbook. McGraw-Hill, New York.

Learn more

• Explore the Materials section to find different construction options for building your home
• Read Renovations and additions to get ideas about how to make your home more energy and water efficient
• Review Designing a home for more information on what to think about when planning your home

Authors

Original author: Department of Health and Ageing 2003

Updated: Department of Industry and Science 2014, Caitlin McGee 2020