How to improve your indoor air quality (sustainably)

Ventilation is the foundation of good indoor air — it dilutes and removes pollutants faster than any filter or plant. Once you have air moving, reducing the sources of pollution is the next most powerful step. Gadgets come last.

Why indoor air matters

We spend, on average, around 90% of our time indoors — at home, in offices, in vehicles. Indoor air can contain higher concentrations of certain pollutants than outdoor air, because homes trap what's generated inside: cooking fumes, cleaning product vapours, moisture, and off-gassing from materials and furnishings. This matters most for people who spend long periods at home, including young children, older adults, and anyone with respiratory conditions.

The aim isn't to create a clinical environment — it's to reduce unnecessary pollutant build-up with a few consistent habits.

Common indoor pollutants (in plain terms)

Knowing what you're dealing with makes the fixes much clearer:

• Cooking fumes and fine particles. Frying, grilling and high-heat cooking release fine particulates and aerosols. Gas hobs also produce nitrogen dioxide (NO₂), a respiratory irritant.
• Moisture and mould spores. Damp conditions — from cooking, showering, drying laundry indoors, or structural issues — allow mould to grow. Mould spores and the volatile compounds they release can affect breathing, especially for people with asthma or allergies. See our full guide to dealing with damp and mould.
• VOCs (volatile organic compounds). These are gases released by many paints, varnishes, adhesives, new furniture, carpets, and some cleaning and personal care products. Levels are often highest when items are new and taper off over time.
• Dust and dust mites. Dust accumulates on surfaces and in soft furnishings. Dust mite allergens are a common trigger for asthma and hay fever symptoms.
• Combustion gases. Gas hobs, open fires, wood-burning stoves and unflued gas heaters all produce combustion byproducts — carbon monoxide, nitrogen dioxide and particulates — that need to be ventilated away.
• Radon. A naturally occurring radioactive gas that seeps from the ground in some geological areas. It accumulates in lower floors and basements. National geological surveys publish maps of affected regions — worth checking if you're in a potentially affected area.

Ventilation — the most effective fix

Opening windows and running extractor fans dilutes and removes pollutants far more effectively than any air purifier or houseplant. Fresh air exchange is the bedrock of good indoor air quality.

• Open windows when you can. Even a few minutes of cross-ventilation — windows on opposite sides of the home, or a window and an interior door — flushes stale air out quickly.
• Use your extractor fan every time you cook. Run it before you start, throughout cooking, and for a few minutes after. If you have a gas hob, this is especially important. If there's no fan, open a window.
• Run the bathroom extractor during and after showering. Shower steam raises humidity sharply; removing it quickly prevents moisture from settling on walls and ceilings where mould can grow.
• Cross-ventilate. Open windows on opposite sides of a room or home to create airflow. Even a narrow gap on a still day makes a difference.
• Don't dry laundry indoors without ventilation. A drying load of clothes releases a significant amount of moisture. Open a window, use the bathroom with the fan running, or use a dehumidifier if outdoor drying isn't an option.
• Trickle vents and mechanical ventilation. Many modern windows have small trickle vents — keep them open. If your home has mechanical ventilation (MVHR or extract fans), keep filters clean and units running.

Reduce pollution at the source

The second most powerful strategy is choosing products and habits that produce fewer pollutants in the first place.

• Choose low-VOC or water-based paints for decorating. Many mainstream brands now offer low-VOC ranges. Ventilate well while painting and for a few days after.
• Be selective with cleaning products. Many multi-surface sprays and air fresheners contain fragrance chemicals that contribute to indoor VOCs. Unscented or fragrance-free alternatives — or simple solutions like diluted white vinegar or bicarbonate of soda — work well for most household tasks. See our eco-friendly cleaning guide for details.
• Avoid aerosol sprays where possible. Spray polish, hairspray and aerosol deodorants release fine droplets and propellants. Roll-on or pump alternatives are lower-impact.
• Manage damp promptly. Fix leaks, improve ventilation in bathrooms and kitchens, and address condensation before it becomes mould. Our damp and mould guide covers this in depth.
• Use a doormat and leave shoes at the door. Shoes track in particulates, pesticides, and other pollutants from outside. A good doormat and a no-shoes habit reduces what enters the home.
• No smoking indoors. Tobacco smoke is one of the most significant sources of indoor air pollution; there's no safe level of exposure.
• Vacuum regularly with a HEPA-filtered vacuum. This removes dust, pet dander and allergens from carpets and soft furnishings without recirculating them into the air.
• Let new furniture off-gas safely. New sofas, mattresses and flat-pack furniture often release VOCs most intensely in the first weeks. Ventilate the room well during this period.

The honest truth about houseplants

You may have read that certain houseplants — spider plants, peace lilies, snake plants — clean indoor air. This claim originates from NASA research conducted in sealed, small chambers in the 1980s. When researchers have tested plant air-purifying effects in realistic room conditions, the effect has been found to be negligibly small: you would need hundreds of plants per room to achieve measurable pollutant removal.

That's not a reason to avoid houseplants. They're pleasant to have around, can improve mood and wellbeing, and some people find them calming. There's also some evidence that contact with soil microbes has benefits. But don't rely on them to clean your air — that's a job for ventilation. See our indoor plants guide for how to care for them sustainably.

One caution: overwatered or densely potted plants in poorly ventilated rooms can add to dampness and, in extreme cases, encourage mould in the soil. Keep pots well-drained and rooms well-ventilated.

Air purifiers — when they actually help

A HEPA air purifier draws air through a fine filter that captures particles down to 0.3 microns — including fine dust, pollen, pet dander, mould spores and some smoke particles. Some models also include activated carbon filters, which absorb certain gases and odours.

Where purifiers genuinely help:

• Households with asthma, allergies or respiratory conditions where particulate reduction matters.
• Homes in areas with poor outdoor air quality (heavy traffic, industrial areas, wildfire smoke seasons).
• Rooms where ventilation is genuinely difficult to achieve.

What they don't do well:

• Remove all gases or VOCs (only activated carbon filters help here, and they saturate over time).
• Replace the need to ventilate or fix the source of pollution.
• Cover very large spaces unless sized correctly — check the CADR (clean air delivery rate) for your room size.

If you decide to buy one, look for a genuine HEPA filter (not "HEPA-type"), a CADR rating that suits your room, and factor in the ongoing cost of replacement filters. Run it on a low, continuous setting rather than high bursts.

Your indoor air quality checklist

• Open windows daily for at least a few minutes, especially after cooking or showering.
• Run the extractor fan every time you cook — before, during and after.
• Run the bathroom fan during and for 15 minutes after showering.
• Check for and fix any sources of damp or condensation.
• Switch to fragrance-free or low-VOC cleaning products where possible.
• Vacuum with a HEPA-filtered vacuum regularly, including upholstered furniture.
• Use a doormat and leave shoes at the door.
• Fit a carbon monoxide alarm on every floor that has a fuel-burning appliance.
• Check your area's radon risk and test if recommended.