Air Purifiers: Choosing One for an Older Adult's Room

What a purifier does

A purifier draws room air through a filter with a fan and releases cleaner air. Common types:

• Mechanical filter (HEPA) purifiers. A pre-filter catches big particles, then a high-efficiency particulate air (HEPA) filter traps fine particles such as smoke, dust, pollen, mould spores and fine pollution particles (PM2.5). A true HEPA filter, in the standard definition, captures at least 99.97 per cent of particles of 0.3 micrometres. Many products labelled "HEPA-type" or "HEPA-like" do not meet this. Look for a recognised grade, such as H13, and a statement of test standard.
• Activated carbon filters. Adsorb some gases and odours, such as cooking smells and certain fumes. A thin carbon layer lasts a short time and does not remove all gases or carbon monoxide.
• Electrostatic and ionising purifiers. Charge particles so they stick to plates or surfaces. Some produce ozone as a by-product.
• Ozone generators are not purifiers and should not be used around people, particularly older adults and anyone with lung disease.
• UV-C and photocatalytic devices. Claims of killing germs are often unproven in practical room conditions, and some produce ozone.

For most households, a HEPA-plus-carbon purifier is the sensible choice.

What a purifier cannot do

• It does not remove carbon monoxide, carbon dioxide or most gas pollutants fully.
• It does not protect against infection in a room shared with an infected person in the way that ventilation, masks and hygiene can; its benefit against germs is limited.
• It does not replace ventilation, removing smoke at source or good housekeeping.
• It does not treat asthma or COPD; medicines and the doctor's plan do.
• It will not help if windows and doors stay open to a polluted outdoor environment.

See indoor air quality for older lungs: dust, smoke and damp for the wider picture, and a pollution season plan for older adults.

The specifications that matter

Clean Air Delivery Rate (CADR). A measure of how much clean air the purifier delivers per hour, tested for smoke, dust and pollen, in cubic metres or cubic feet per hour. Higher is better for bigger rooms. Check that the CADR is from an independent test, such as that by an industry certification programme, and not an unexplained claim.

Room size. A common rule of thumb is that the CADR for smoke should be roughly two-thirds of the room's floor area in square feet (the manufacturer states a recommended room size). Or aim for four to five air changes per hour: multiply the room volume by 4 or 5 and divide by 60 to find the minimum clean air volume per minute. For a ten by twelve foot bedroom with an eight-foot ceiling, that is about 960 cubic feet; at five air changes per hour, you need about 4,800 cubic feet per hour of clean air. In dusty Indian cities, aim for the upper end, and choose a unit rated for a larger room than yours. Do not buy by the largest area printed on the box without checking the CADR.

Filter grade and quality. Look for true HEPA, with a sealed housing, so that air cannot bypass the filter. Check the replacement filter availability in India and whether filters can be bought from several sellers.

Noise. A purifier running all night must be quiet at the settings that matter. Look at noise levels in decibels at low and medium speed, and note that the quietest setting often has the lowest CADR. Some older adults with hearing loss like a steady hum; others find noise disturbing.

Power use. Check the wattage and the cost of running it for many hours.

Controls and display. Simple knobs, a clear filter-change indicator and an air quality indicator light are helpful. A child lock avoids accidental changes. Avoid features that need an app or Wi-Fi unless they are really useful for you.

Auto mode and sensors. An automatic mode that adjusts fan speed to the sensor reading can save electricity, but low-cost sensors are imprecise; see air quality monitors for homes with older adults. Manual control is fine.

Ozone and certification. Choose a model that states it meets limits on ozone emissions, and avoid ionisers and any device that makes ozone deliberately. Ask for certification details.

Build and safety. Stable base, a protected fan, cord management and safe materials. Check the warranty and service support in your city.

Placing and using it

• Put it in the room where your parent spends most time, usually the bedroom, and run it with the doors and windows closed to get the benefit. A purifier in an open room is much less effective.
• Keep space around the unit: follow the maker's distances from walls and furniture, often 30 to 50 cm, so air can enter and leave.
• Place it at a height away from the floor if the maker advises, and away from the bed head directly in front of the face, because a direct draft may cause discomfort.
• Do not put it near a kitchen, bathroom steam or heater.
• Run it continuously at a quiet setting during pollution seasons, rather than only for short bursts. On a very polluted day, run it at a higher speed for the first hour, then at a quieter setting.
• Combine with source control: no smoking, incense, mosquito coils or sweeping dry.
• Ventilate carefully: brief ventilation when outdoor air is better and CO2 builds up; see temperature and ventilation at home.
• Keep it clear of curtains, bedding and clutter.
• Do not block the air outlet with blankets or by placing it in a cupboard.
• If oxygen is used, keep the purifier's electrical parts away from oxygen equipment and follow the safety rules; see safe use of oxygen and electrical equipment.

Realistic benefits

Studies show that HEPA purifiers can lower indoor fine particle levels substantially when used in a closed room, and some studies suggest modest improvements in symptoms, blood pressure or lung function in people with respiratory or heart conditions, though results vary and the evidence is not strong in every group. Benefits depend on how much of the day is spent in the purified room, how leaky the home is and how polluted the outdoor air is. Treat a purifier as one layer of protection alongside medicines, clean cooking, avoiding smoke and following the doctor's advice.

Costs and upkeep

Costs vary widely, and the price of replacement filters over the years can exceed the price of the machine. Before buying, check how often filters need changing, what they cost and whether they are easy to buy. Also consider electricity. See air purifier filters: replacement, costs and maintenance.

Beware of marketing claims

• "Kills 99.9 per cent of viruses" without test details.
• "Hospital grade" or "medical grade" with no standard cited.
• "Removes all pollutants."
• "Negative ion technology" or "plasma" without ozone certification.
• "Lifetime filter."
• Very small, cheap units claimed to cover large rooms.
• Pressure to buy extra "anti-bacterial" accessories.

See spotting fake or poor-quality care products and medical device licences and safe buying.

When a purifier is not enough

If your parent is breathless, wheezy or coughing more in polluted seasons, tell the doctor, who may adjust treatment. A purifier cannot replace an inhaler, a nebuliser, vaccines or oxygen. See COPD at home guide and asthma in older adults.

When to ask a professional

Ask your doctor whether air quality is likely to be affecting your parent's lungs, and for a pollution-day plan. Ask a pharmacist about masks. Ask the seller for the CADR test report and ozone certification. Call the doctor if breathlessness or cough worsens. Call 112 for severe breathlessness, blue lips, confusion or chest pain.