Indoor air quality can be more than three times worse than outdoor air quality, according to a study by UK air pollution campaigners Clean Air Day.
Find out how you might be unwittingly generating air pollution in your home, and what you can do to improve your indoor air quality.
We all know that outdoor pollution is a problem, but the chances are you don't worry too much about the quality of the air in your own home.
Yet many of the things we do to make our homes more comfortable, such as decorating, lighting candles and using air fresheners, can increase our personal exposure to pollutants – and contribute significantly to our collective national emissions.
This isn't something we should ignore.
If you're elderly or you have a pre-existing health condition, such as asthma, heart disease or chronic obstructive pulmonary disease (COPD), you're particularly vulnerable to the effects of pollution.
Children and young adults are also more vulnerable, because they have faster breathing rates and their lungs are still developing.
Even if you're currently healthy, you're still at risk of developing health problems as a result of polluted indoor air.
There are three main types of pollution in our homes: particulate matter (PM), gases and volatile organic compounds (VOCs).
Particulate matter is generated as a by-product of combustion (or, in layman's terms, burning something). This can be when you use a wood or coal fire, but also as a result of more common activities - such as burning candles, using electric toasters and cooking with gas.
Regular cleaning can help get rid of particulate matter – in theory. But cleaning 'the wrong way' risks simply stirring up particular matter that's settled as dust, and lifting it into the air. This can happen if, for example, if you dry dust, or use a poorly performing vacuum cleaner. Look for a vacuum cleaner with good allergen retention, and dust with a damp cloth if possible to prevent this happening.
Particulate matter can inflame your airways and increase the risk of lung and heart disease if inhaled at persistently high levels over time.
Gases – including carbon dioxide (CO2), nitrogen dioxide (NO2) and carbon monoxide (CO) – are emitted by appliances that burn fuel, such as open fires, gas cookers and gas boilers.
Don't assume every carbon monoxide detector is up to the job of protecting you and your family. Our tests have uncovered carbon monoxide alarms that can't be relied upon to detect the gas and sound the alarm. Discover our .
Volatile organic compounds (VOCs) are chemicals found in a wide variety of materials. They're produced when cooking and using heating appliances, such as wood burners and non-electric space heaters, as well as when everyday household products such as paint or furniture polish are used. VOCs evaporate into the air at room temperature, forming vapours that we breathe.
Different classes of VOCs have different risk levels. For example, benzene is a carcinogen (from petrol and cigarette smoke and, potentially, from paints and solvents) and is high risk. Terpenes, including limonene and pinene (familiar lemon and pine smells used in scented toiletries and bathroom cleaners), are considered lower risk.
VOCs can react with ozone from outdoor air, particularly in hot weather, to form the gas formaldehyde and other irritants. Formaldehyde is a lung irritant that can cause allergic reactions and, at very high levels, is carcinogenic. Formaldehyde can also be released from new flatpack furniture, lino and carpet, fabrics, bedding, glues and insulation.
Exposure to very high levels of VOCs can cause symptoms such as eye, nose and throat irritation, headaches and nausea and, in the long term, even damage the liver, kidneys and central nervous system.
If you're concerned about the air quality in your home, it can be tempting to assume you need an air purifier. These are increasing in popularity and, if you do want one, our reviews of the can help you choose the right one for your home.
However, an air purifier shouldn't be your first line of defence against pollution. First take these simple steps to improve your home's air quality.
Opening your windows regularly is the an easy to remove polluting particles from the air in your living space and let fresh air in.
Don't forget to do this in winter, when humidity is high, however tempting it is to keep all windows tightly closed.
However, you must be strategic about when you do this. If you live near a busy road, keep the windows closed at peak traffic time. 2022 research by the Building Engineering Services Association (BESA) found that opening a window to let in fresh air could be counterproductive in many cases, and actually worsen indoor air quality.
The study found that:
believed that the air near their home was 'very clean' or 'fairly clean'. But, according to the BESA, 'All of these create millions of tonnes of highly damaging air particles which enter our bodies and can remain for up to three months'.
If you suffer from hay fever, don't open your windows in the morning, when the pollen count is highest.
The BESA recommends monitoring your local pollution levels, keeping windows open for longer on days when pollution levels are lower and for less time when pollution levels are higher.
Cooking produces grease, smoke, smells and moisture. Switch on your kitchen hood and fans during and after cooking – even if you find them annoyingly noisy – to clear the air of oil and other ingredients that have evaporated into it. This will also limit damage to your walls and kitchen cabinets.
If you can, get an extracting cooker hood, sometimes called a vented hood or ducted hood, rather than a recirculating one. Extracting hoods send the air out of your home through the wall or roof, while recirculating models filter the air through a carbon filter and recirculate it inside your kitchen. If you have a recirculating hood, make sure you clean and change the filter regularly.
Meanwhile an extractor fan can be installed in any room where you want to control humidity, gas or smoke. An extractor fan in your bathroom can pull moist air out of the room, preventing mould spores growing. It can also remove the after effects of using toiletries and cleaning products.
Avoid blocking or decorating over existing permanent ventilation features, such as air bricks and trickle vents on windows, even if you've heard that doing so could help you save on your heating bill.
They are there to allow air to circulate naturally when windows and doors are closed.
They also allow oxygen in, moderate internal temperatures, reduce the risk of condensation, and prevent pollutants building up inside.
In 2017, we carried out an investigation into indoor air pollution in three houses: one from the Victorian era, one from the 1950s and one new-build. We performed a range of everyday tasks in the houses – vacuuming, cleaning, using air fresheners and candles, cooking a fry-up and burning toast – and measured the air quality in each of the houses before and afterwards.
We found the highest levels of air pollution were in the 1950s house, where home improvements such as cavity wall and roof insulation, double glazing and other energy-efficiency measures had made the house overly airtight.
Of course, it's all a balancing act as these measures can also help reduce your energy bills and lower your carbon footprint. But it's important not to turn your home into a tightly-sealed box.
Make sure you vacuum often to remove polluting particles.
The best vacuum cleaners will pick up twice as much dust as the worst, and they’re much better at stopping particles leaking back out into your room.
Carpets can harbour allergens, so it's important to vacuum these often, especially if you're in a rental property. If you suffer from allergies, and have the option to, it's a good idea to replace your carpets with solid flooring, which will be much easier to clean.
It's particularly important to vacuum if you have pets, as pet dander can add to the air pollution in your home. Dogs and cats naturally shed old hair – some twice yearly, some all the time.
Pollen can also attach itself to your pet's fur and be carried indoors, which isn't ideal if you're a hay fever sufferer, so keep your pet off your bed, in particular, if you can.
Consider the following when choosing a vacuum cleaner:
When pet hair is trodden into carpets or rugs it can be hard to get out, as it tangles in the carpet fibres. We run our vacuum cleaners through a specific pet hair test. Some, including ones that are great in other respects, really struggle with pet hair, leaving you going over the same spot again and again.
Equally, some that are specially designed for pet hair are less effective than all-round models.
We also test how well each vacuum cleaner retains the particles it sucks up.
However hard and often you clean, you'll never get your house free of dust, but you can reduce it. Don't wear shoes indoors, wash bedding regularly and take non-washable items outside to shake clean.
Nice (the National Institute for Health and Care Excellence) says that you should avoid buying a second-hand mattress if you're allergic to dust mites.
High humidity levels can cause respiratory problems, and provide a perfect breeding ground for mould spores, dust mites, clothes moths, fleas, cockroaches and other nasties.
If you've got asthma or a weakened immune system, you should take particular care to keep humidity levels in your home in check. According to the charity Asthma UK, 42% of asthmatics surveyed said that mould and fungi triggered their asthma.
Avoid hanging wet washing indoors. You might not have any other option if you don’t have a tumble dryer or an outdoor clothes line, but when moisture in the air meets cold surfaces, such as windows and walls, it condenses.
If you must dry your washing indoors, open a window so water vapour can escape, or use a dehumidifier and close the windows and doors of that room (otherwise you're making the dehumidifier work even harder).
Use a clothes airer rather than hanging your washing directly on the radiator, which can cause condensation, add to your heating bills, damage the delicate fibres in your clothes and complicate your case if you're renting and trying to get your landlord to do something about your damp problem. It can even be a fire hazard.
Set your clothes horse up in the sunniest spot in your home (unless that’s your bedroom, as you should avoid drying clothes in the room you sleep in).
Don’t put damp clothes back in your wardrobe. Getting mould out of a wardrobe can be a nightmare, as you can’t just set to it with mould remover and a stiff-bristled brush because this could damage the materials.
A dehumidifier can help to keep your home's humidity levels in check and prevent mould developing. Head to our to find out more. If your damp problem is advanced, use our guide to to find out what your options are.
When painting, decorating and cleaning, make sure that the room is well ventilated. Chemicals found in everyday products, such as paints, aerosols and cleaning products with limonene and pinene (familiar lemon and pine smells), can emit VOCs.
Exposure to very high levels of VOCs can cause eye, nose and throat irritation, headaches and nausea. In the long term they can also cause damage to the liver, kidneys and central nervous system.
If you've got asthma, look for paint that is labelled low in VOCs to minimise your exposure. After decorating, wait for paint and solvent smells to subside before using the room again.
Reduce your use of easily inhaled sprays, aerosols and furniture polish (dust with a damp cloth or electrostatically charged duster instead). Scented candles and air fresheners can also be a culprit for air-borne irritants; if there's an unpleasant odour in your house, track down and deal with the source rather than trying to drown it out.
NICE says that women who are pregnant, and babies under 12 months, at are increased risk from exposure to poor indoor air quality. According to NICE, pregnant women, new mothers and people who live with them 'should reduce their use of household sprays, air fresheners and other aerosols and always follow product instructions', 'avoid activities that produce particulate matter such as using candles' and 'always keep the room well ventilated during these activities'.
Consider switching to ways of cleaning that are less polluting than household aerosols and sprays.
Be aware that, when it comes to marketing, words such as 'green', 'natural' and 'eco-friendly' are often meaningless, as there's no regulation around their use. The same applies to images of flowers, trees, blue skies and oceans.
If you need (or prefer) to use shop-bought cleaning products, two simple tips are to choose cream cleaners over spray cleaners, and scentless or low-scent products if you can. The less fragrance, the less reactive chemistry there is likely to be.
Avoid using unvented (also known as vent-free) appliances such as freestanding gas and paraffin heaters. These may sound convenient, as they don't require a vent pipe or chimney, making them easy to install, but they release a number of harmful pollutants into your room.
All gas heaters, even when burning properly, produce carbon dioxide (CO2). When carbon dioxide builds up, it results in drowsiness, dizziness and headaches, creating an impression of a stuffy, closed house.
You might be reliant on a wood-burning stove for heating. However, if you've got asthma, or a condition that puts you at greater risk from indoor air pollution, think carefully before using a wood-burning stove. Both Asthma UK and the British Lung Foundation recommend avoiding them.
A 2020 study by researchers at the University of Sheffield and the University of Nottingham found that residential stoves released high intensities of PM2.5 and PM1 – particulate matter already identified by the World Health Organisation (WHO) as a very serious health risk, able to penetrate your lungs and enter your blood stream. Researchers installed air quality monitors in the homes of people with log burners and measured the level of harmful particulate matter over a four-week period.
If you already have a wood-burning stove or fire, you should burn only untreated, fully dried wood with a moisture content of 20% or less. This will be labelled as 'Ready to Burn'. Some types of fuel, such as wet logs and house coal, produce far more particulate matter than dry logs and low-sulphur smokeless fuels, such as anthracite coal.
When wood doesn't have a good-enough supply of oxygen, it creates more smoke and potentially harmful emissions. It also increases sooty build-up in your chimney. Make sure the flue damper is open before you use it. Clean the flue and chimney often so that smoke has a means to escape.
Keep the fire constant, so that the flue stays at the right temperature. This will help to avoid carbon monoxide (CO) coming down the chimney.
If you're considering buying a wood-burning stove, make sure you're aware of the environmental and health implications for you and your neighbours.
Although new Ecodesign regulations came into force in January 2022, many scientists remain extremely concerned about the impact even of the new wood-burning stoves on our indoor air quality.
You don't need us to tell you about the dangers of smoking. You might be surprised to learn, though, that when you smoke, more smoke gets released into the air – where others can breathe it in – than goes into your lungs.
The NHS says that second-hand smoke (the smoke you exhale, plus the sidestream of smoke from your cigarette end) puts your family at risk from the same diseases as smokers, such as lung cancer and heart disease. Children living in a smoky house also have a greater chance of developing asthma, breathing problems and other allergies.
Smoke can linger in the air for hours after you've finished smoking, and it can spread from room to room. Opening a window or door won't banish the smoke, as it can blow back inside and stick to surfaces such as soft furnishings, to be released later, sometimes in more harmful forms (third-hand smoking).
The London Fire Brigade warns that smoking indoors is also a major cause of fire fatalities. If you're going to smoke, go outside, close the door behind you and move away from the house.
Remember you're still bringing smoke particles back in with you via your clothes.
Buying an air purifier shouldn't be the first or only thing you do to reduce your indoor air pollution: first, deal with the problem at its source by minimising any pollution you're creating.
But, as well as taking the above steps, you could consider an air purifier. An air purifier could be particularly useful if you have allergies or respiratory problems, live near a major road or industrial facility, or you're often exposed to second-hand smoke or odours you have no control over.
Air purifiers aren't perfect as they don't offer a solution to the problem of air pollution. But they can reduce the level of pollution you breathe in. As they come with a maximum room capacity, they'll only be able to clean the air in one room rather than your whole house.
We test each air purifier with dust particles, cigarette-smoke particles and pollen, so we can tell you which do the best job of removing these pollutants.
Clearly, if you're renting you're going to have less control over the indoor air quality in your home than if you owned your own place.
Contact your landlord if:
If your landlord is uncooperative and refuses to take any actions, contact your local council. In March 2019, a new law came into force to make sure rented houses and flats are 'fit for human habitation'. In other words, they must be safe from things that could cause you serious harm.
Depending on your tenancy agreement, if the property you're renting falls short of this, you can take your landlord to court (the Homes Act).
Even if your tenancy agreement means you don't have recourse to the Homes Act, you should still contact your local council if you're worried about conditions in your home, and it can take action on your behalf.