Is air conditioning bad for your health?
No, not for most people. UKHSA's Beat the heat: staying safe in hot weather guidance, updated 21 July 2026, tells anyone with signs of heat exhaustion to "move to a cooler place such as a room with air conditioning". The health downsides people worry about are real but smaller and fixable. The NHS lists air-conditioned rooms as one cause of dry eyes. A unit left with clogged filters can smell and circulate dust. Very long runs in drying mode can take the air below the humidity range that suits most people.
What a home air conditioner does not do is give you a cold. The NHS page on colds says plainly that colds are caused by viruses. A sore throat after a night with the unit on is far more likely to come from dry air or air blowing straight at you, and both are settings problems.
This page sticks to what named health bodies say, plus physics you can check with a calculator. It is not medical advice. If you have a heart or lung condition, ask your GP or respiratory nurse what room temperature suits you.
What UK health bodies actually say about air conditioning
Here is what the main bodies we checked in November 2026 say.
- UKHSA names "a room with air conditioning" as a place to cool down if you or someone else has heat exhaustion symptoms, alongside shade, cool drinks and cool water on the skin.
- The NHS says you are more likely to get dry eyes if "you spend time in air conditioned or heated environments", and advises not to spend too long in air conditioned or heated rooms.
- The NHS lists air conditioning systems among the sources of Legionnaires' disease, with hotels, hospitals and offices the usual settings. It says catching it at home is less common.
- The World Health Organization's heat fact sheet says that if you use air conditioning, set it to 27°C and add an electric fan, which it says makes the room feel 4°C cooler and can cut the cooling bill by up to 70%.
- Asthma + Lung UK says hot and humid air can make breathlessness and wheezing worse, and advises people with lung conditions to keep their home between 18°C and 26°C.
None of them says home air conditioning is harmful in itself. The cautions are about dry air, maintenance and large building water systems.
Why heat is the bigger health risk in a Leeds summer
UKHSA estimates that 2,803 people aged 65 and over died because of the heat in England in 2022, the summer when temperatures passed 40°C in the UK for the first time on record. Hot weather can raise the risk of heart attack, stroke and lung problems, and UKHSA now puts everyone aged 65 and over on its higher-risk list, down from 75.
West Yorkshire is not exempt. The Met Office historic station data for Bradford gives a provisional July 2026 mean daily maximum of 23.1°C, against a 1991 to 2020 July average of 20.4°C.
UKHSA and the Met Office run Heat-Health Alerts from 1 June to 30 September. Yorkshire and the Humber, which includes West Yorkshire, uses the same decision thresholds as every region outside London. A maximum daytime temperature of 27.0°C to 29.9°C is the "low" impact band, linked to about 10% more deaths than expected. 30.0°C to 37.9°C is "medium", at about 20%. Above 38.0°C is "high", at about 50%. The guide warns against ignoring yellow alerts: summer 2023 had over 2,000 heat-associated deaths, and the worst daily rate came during a yellow alert.
UKHSA's keep cool at home checklist lists the homes most likely to overheat, and two types are common in Leeds. Top-floor flats are on it, including many of the apartment blocks covered in our Leeds city centre flat guide. So are homes with opening windows on one side only. That is every back-to-back, and the Leeds Housing Strategy counts about 19,500 pre-1919 back-to-back houses still in use.
Does air conditioning dry out the air?
Yes, in cooling mode it removes water, but on a muggy summer night that usually moves a bedroom towards a comfortable humidity, not past it. You can check this yourself with two numbers: how much water a cubic metre of air can hold at a given temperature, and how much it actually holds.
Take a double bedroom 4.0m by 3.5m with a 2.4m ceiling. That is 4.0 x 3.5 x 2.4 = 33.6 cubic metres of air. Say it is 26°C at 60% relative humidity on a close July night. Using the standard Magnus formula for saturation vapour pressure, air at 26°C can hold about 24.3g of water per cubic metre, so at 60% it holds 24.3 x 0.60 = about 14.6g per cubic metre.
Now cool that same air to 22°C. Air at 22°C can hold only about 19.4g per cubic metre. If no water came out, the humidity would rise to 14.6 / 19.4 = about 75%, which would feel clammy. The dew point of the original air is about 17.6°C, and the indoor coil of a split unit runs colder than that, so water condenses on it and runs out through the drain pipe. To land at 22°C and 50% the room air must drop to 19.4 x 0.50 = about 9.7g per cubic metre. That is 14.6 minus 9.7 = 4.9g taken out of each cubic metre, or 4.9 x 33.6 = about 164g for the whole room. Roughly a small glass of water.
In summer, people, cooking and outdoor air keep adding water, so a cooled room in a Leeds heatwave rarely ends up desert dry. Dry air is more of a winter story, for radiators as much as heat pumps. Outdoor air at 5°C and 90% humidity holds about 6.1g per cubic metre. Warm it to 21°C indoors, where air can hold about 18.3g, and the humidity falls to 6.1 / 18.3 = about 33%, with no air conditioner involved.
If your throat or eyes feel dry, check the mode. Daikin's user guide for its FTXM wall units describes drying mode as decreasing the humidity in a room with no temperature setting, so on a mild day it can overshoot.
What humidity should a room be?
The figure most often cited comes from a review by Sterling and colleagues in Environmental Health Perspectives, Indirect health effects of relative humidity in indoor environments. It concluded that most of the health effects linked to humidity would be kept low by holding indoor levels between 40% and 60%. It also found dust mite populations are smallest below 50% and largest at 80%, and that most fungi cannot grow unless humidity is above 60%.
That gives a target band with a reason at each end. Below 40% is where dry eyes and throats are more likely. Above 60% is where mould and mites gain ground. A cheap digital hygrometer on the bedside table tells you which side you are on.
Asthma + Lung UK makes the same point from the other direction in its advice on improving indoor air quality. It says dehumidifiers can help prevent condensation but can make the air too dry and cause coughing, and that a good one lets you set a balanced level.
Dry eyes, dry throat and cold draughts
The NHS dry eyes page puts air-conditioned and heated rooms on its list of things that make dry eyes more likely, along with long screen time, contact lenses and being over 50. If you get dry eyes, check the hygrometer first. If the room is under 40%, switch from drying mode to cooling, raise the set point and take screen breaks. The NHS also suggests a humidifier.
Airflow direction causes as many complaints as humidity. UKHSA's checklist says not to aim an electric fan directly at your body because it can lead to dehydration, and Daikin's FTXM user guide says never to expose little children, plants or animals directly to the airflow. Point the louvres at the ceiling, away from the bed and sofa.
Allergies, asthma and what the filter really catches
Every split unit we have looked at has a washable mesh filter behind the front panel. Daikin's maintenance advice says these filters "capture dust, pollen and other particles", and asks owners to clean them every two weeks in heavy use, more often with pets, smokers or allergies in the home. A dirty filter is the usual cause of a musty smell. Daikin's FTXM guide says a unit run with dirty filters cannot clean the air and causes odour.
A mesh filter is a dust filter, not a medical air purifier. If allergy relief is the main reason you are buying, ask which filter grade the unit has. Ventilation filters are graded under ISO 16890. Camfil's explainer on ISO 16890 sets out the groups: ePM1, ePM2.5 and ePM10 mean the filter captures at least 50% of particles in that size range, and anything below 50% of PM10 is graded Coarse. If a brochure gives no ISO 16890 class, treat the unit as a dust filter and judge it on that.
For dust mite allergy, humidity does more than the filter. Asthma + Lung UK's page on air pollution and allergies at home says dust mites like warm, humid, damp places, and suggests lowering humidity, washing bedding at 60°C and using a vacuum with a HEPA filter.
Asthma + Lung UK suggests checking pollen and pollution levels before opening windows if they trigger your symptoms. A split unit recirculates the room's own air, so you can keep windows shut on a high pollen day and stay cool. The trade-off is fresh air, covered below.
Damp is the allergy risk most Leeds homes should worry about first. The government's guidance on the health risks of damp and mould estimates damp and mould in English homes were associated with about 5,000 cases of asthma and 8,500 lower respiratory infections in 2019.
Is air conditioning good for COPD?
No health body we found recommends air conditioning as a COPD treatment, and you should not treat it as one. What the sources do say is about temperature and humidity, and that is where a unit can help someone with COPD stay within the advice.
Asthma + Lung UK's hot weather advice says hot and humid air can affect breathing and make breathlessness and wheezing worse, and that in its survey 1 in 3 people said hot weather made their symptoms worse. It advises keeping the home between 18°C and 26°C. Its cold weather advice covers the other end: 7 in 10 people told the charity cold air made their lung condition worse, and it advises heating the rooms you use most, such as the living room or bedroom, to at least 18°C.
A reversible split unit covers both ends of that 18°C to 26°C band. In summer it can hold a bedroom below 26°C on nights when opening a window brings in hot air. In winter the same unit heats, which is why installers call it an air-to-air heat pump, and our air-to-air heat pump guide covers what that costs against gas in Leeds. Keep the air off the face, humidity above 40% and the filters clean.
Asthma + Lung UK also advises keeping a self-management plan. A cooler room is no substitute for that or for prescribed medicines. If heat or cold makes your symptoms worse, tell your GP or respiratory nurse.
Can air conditioning make you ill? Legionnaires', refrigerant and stale air
Legionnaires' disease is the worry that comes up most, and the NHS page on Legionnaires' disease does list air conditioning systems as a source. The HSE explains where the risk sits. Its Legionnaires' guidance says outbreaks come from purpose-built systems that keep water at 20°C to 45°C and can spray fine droplets into the air, such as cooling towers, evaporative condensers, hot and cold water systems and spa pools. A domestic split system has no cooling tower and no water tank. Its water is coil condensate that runs out of a drain pipe.
Refrigerant leaks are rare but worth knowing about. Daikin's FTXM user guide describes the R32 refrigerant as mildly flammable and says it normally does not leak. If a leak reaches a flame from a heater or cooker it can cause fire or a harmful gas, so turn those off, ventilate the room and have an engineer repair it before using the unit again.
Stale air is the third. A split unit cools and filters the air already in the room. It does not bring in fresh air. Daikin's guide says to keep doors and windows closed while it runs, and also to ventilate often, with extra attention to ventilation during extended use. Open a window for a few minutes morning and evening and keep trickle vents open.
Sleep: a cooler bedroom without the side effects
The NHS sleep advice on Every Mind Matters says you may find it easier to sleep in a room that is quiet, dark and cool. Our bedroom air conditioning guide covers the quiet part, comparing portable and split noise against WHO night limits.
For health and sleep together, start from the WHO figure. Set the unit to 27°C with a fan running on a heatwave night, or 25°C to 26°C if that still feels too warm, which keeps you inside the Asthma + Lung UK upper limit of 26°C. Use sleep mode or the timer so the unit eases off after you fall asleep.
Cost need not stop you using it during an alert. Ofgem's price cap for 1 October to 31 December 2026 puts the Yorkshire region electricity rate at 25.60p per kWh by Direct Debit. Our running costs guide works out that a common 2.5kW wall unit draws about 0.28kW at its certified 30°C part-load point. Over an 8-hour night that is 0.28 x 8 = 2.24kWh, and 2.24 x 25.60p = about 57p. A four-night amber Heat-Health Alert would cost about 4 x 57p = £2.29 for one bedroom.
A health checklist for running air conditioning at home
Run through this when the unit is fitted and again each summer.
- Put a digital hygrometer in the main bedroom and aim for 40% to 60% humidity.
- Use cooling mode in hot weather and save drying mode for damp, mild days.
- Set 25°C to 27°C on hot nights, adding a fan if needed, and stay below 26°C if anyone in the house has a lung condition.
- Angle the louvres to the ceiling, never at a bed, a cot or a sofa.
- Clean the mesh filters every two weeks in heavy use, and dry them in the shade before refitting.
- Ventilate for a few minutes each morning and evening and keep trickle vents open.
- Do not run the unit while using a fumigation-type insecticide, which Daikin warns can collect in the unit.
- Book a professional service once a year. Daikin recommends spring or autumn, and our air conditioning servicing in Leeds page explains what a service covers.
Getting a system fitted in Leeds and West Yorkshire
If you are fitting air conditioning partly for health reasons, say so when you ask for a quote. It changes what to ask: where the indoor unit can go so air does not blow across the bed, which filters the model carries and whether it should heat in winter too. Our home air conditioning in Leeds page covers the usual options for houses and flats.
Our partner installers are MCS certified and zero-rate VAT on domestic installs. They cover Leeds and its suburbs first, then Bradford, Wakefield, Harrogate and Huddersfield. Request a free quote with the room, your postcode and who will use it, and we will pass it to an installer near you.