00WHAT THE GUIDANCE SAYS

Let the room
breathe.

A bright living room with a sash window pushed open, a sheer curtain lifting in the breeze and a potted plant on the sill — AI-generated image, not a photograph of a real person or place.

Most of our air is breathed indoors.

Cooking, showers, drying clothes and cleaning sprays all add to it. UK and US health guidance comes back to one habit: let the stale air out at the moments that make it.

OPEN UPat the right momentUpdated 14 October 2026

Check a room

01Principles

Fan on when cooking
Steam out after showers
Spray less, air more
Small habits, fresher rooms

02THE SHORT ANSWER

Ventilate when you
make the mess.

Indoor air changes with what we do.
Guidance focuses on a few everyday moments.

COOKING

Fan on, every time

NICE says cookers, especially gas cookers, can make indoor air worse. Use the extractor or open a window while you cook.

Check the kitchen

DAMP

Let the steam out

Showers, boiling pans and drying clothes add moisture. Guidance pairs extractor fans with background ventilation such as trickle vents.

How to do it

SPRAYS

Air out after cleaning

Sprays, aerosols and paints release chemicals into the room. Follow the label and open up while you use them.

See the numbers

03A QUICK ROOM CHECK

What is happening
in the room?

Pick an everyday activity to see how much extra fresh air the guidance suggests. The bar shows how strongly the guidance points to ventilating.

Based on NICE guideline NG149 on indoor air quality at home. This is general information, not personal medical advice.

Room check

Choose an activityReading on the sofaCleaning with spraysCooking on gasA hot showerDrying clothes inside

Reading on the sofaBackground air

Nothing extra to clear. Keep background ventilation working, such as trickle vents left open, so the room never seals up completely.

Cleaning with spraysOpen up

Increase ventilation while you use sprays, aerosols or paints and follow the instructions on the label. People with asthma may do better with non-spray products.

Cooking on gasFan on

Use the extractor fan or open a window while you cook. NICE singles out gas cookers and says never to use one to heat a room.

A hot showerFan on

Run the bathroom extractor fan to clear the steam. If a rented home's fan is broken or too noisy to use, the guidance says to tell the landlord.

Drying clothes insideAvoid if you can

Avoid drying clothes indoors where possible. If you have to, improve the ventilation in that room while they dry.

Source: NICE guideline NG149, Indoor air quality at home (2020), recommendations for the public.

04TWO NUMBERS WORTH KNOWING

We live indoors,
so does the pollution.

One figure on where we spend our time,
one on how indoor air compares with outdoors.

≈ 90%

Share of time spent indoors

The US Environmental Protection Agency says Americans spend about 90 percent of their time indoors. England's Chief Medical Officer put the figure at around 80 percent in his 2022 report.

TIME INDOORS · US EPA

2–5× higher

Some pollutants, inside vs outside

The EPA says the concentrations of some pollutants are often 2 to 5 times higher indoors than typical outdoor levels.

INDOOR LEVELS · US EPA

England's Chief Medical Officer noted in December 2022 that indoor air pollution has been studied less than outdoor air, and called for effective ventilation that also keeps energy use and heat loss down.

05FOUR HABITS TO TRY

Fresh air,
without the draught.

None of these needs new equipment. They are about using the vents and fans most homes already have at the moments that matter.

Turn the hood on before the pan
Start the cooker extractor when you start cooking and leave it running a little after.
Leave the trickle vents open
Background ventilation keeps a slow, steady change of air without opening a window wide.
Fan on in the bathroom
Clear shower steam with the extractor fan so moisture does not settle and feed mould.
Choose fewer sprays
Where products trigger symptoms, NICE suggests non-spray alternatives, and more air while you clean.

Towels and shirts drying on a wooden clothes airer beside an open window, with an extractor vent on the wall — AI-generated image, not a photograph of a real person or place.

06DAMP AND MOULD

Moisture is
the hidden load.

A pan steaming on a gas hob under a stainless steel cooker hood that draws the steam upwards — AI-generated image, not a photograph of a real person or place.

Everyday life puts water into the air: cooking, washing, showers and drying laundry. Without a way out, it condenses on cold walls and windows, and damp and mould follow.

NICE recommends using background ventilation and extractor fans, opening windows when it is safe, avoiding moisture-producing activities indoors where possible, and repairing water damage promptly.

07Questions

Questions people ask

Is indoor air really worse than outdoor air?

Sometimes, for some pollutants. The US EPA says concentrations of some pollutants are often 2 to 5 times higher indoors than typical outdoor levels, and people spend most of their time inside.

Do I need to open a window when cooking?

Guidance says to increase ventilation when cooking, using an extractor fan or opening a window if it is safe. NICE highlights gas cookers in particular and says not to use a gas cooker to heat a room.

What are trickle vents for?

They are small vents, often in window frames, that let a little air in all the time. NICE advises learning how to use them and, for tenants, telling the landlord if they are blocked or damaged.

Is it bad to dry clothes indoors?

NICE advises avoiding air-drying clothes indoors where possible because it adds moisture to the air. If you need to, improve the ventilation in that room.

Who is most affected by poor indoor air?

NICE lists older people, pregnant women, young children, people with existing medical conditions and people who spend a lot of time at home as being at higher risk.

08Sources

Let the room
breathe.