Air Quality Monitors for Homes With Older Adults

What an air quality monitor measures

Home monitors typically report some of the following:

• PM2.5: fine particles smaller than 2.5 micrometres, from smoke, traffic exhaust, burning, cooking and dust. They reach deep into the lungs and bloodstream. This is the most important number for health.
• PM10: larger particles such as road dust, pollen and construction dust.
• CO2 (carbon dioxide): not a pollutant at home levels but a good indicator of ventilation. High levels mean stale air in a closed room with many people.
• TVOC (total volatile organic compounds): gases from paints, cleaning products, fragrances, mosquito coils and incense. The reading is rough and not very specific.
• Temperature and humidity: useful for comfort and for damp, mould-prone rooms.
• Formaldehyde (HCHO) on some models, relevant after new furniture or paint.
• Carbon monoxide (CO) is measured by dedicated alarms, not by most general air monitors. A CO alarm is a safety device, not just a monitor, and is important wherever gas heaters, charcoal, kerosene or generators are used indoors.

Understanding the numbers

PM2.5 and AQI. Many devices and apps show PM2.5 in micrograms per cubic metre and/or an Air Quality Index. India's national AQI, used by pollution control authorities, has categories commonly described as Good, Satisfactory, Moderate, Poor, Very Poor and Severe, rising through 0 to 500. Other countries use slightly different scales. The World Health Organization's 2021 air quality guidelines recommend much lower levels than most countries' standards: a 24-hour average PM2.5 not exceeding about 15 micrograms per cubic metre, and an annual average of about 5. Most Indian cities exceed these levels for much of the year, so reaching the WHO values indoors may not be realistic. Use the numbers as a relative guide: lower is better.

CO2. Outdoor air has roughly 400 to 450 parts per million (ppm). Indoors, readings of about 800 to 1,000 ppm or more suggest poor ventilation, and above that, stuffiness, headaches and tiredness can appear. In a bedroom with the door and windows shut overnight, CO2 can climb high.

Humidity. Around 40 to 60 per cent relative humidity is comfortable. Above 60 to 70 per cent, damp and mould are more likely, which can irritate older lungs. Very dry air can irritate airways.

Accuracy: what low-cost monitors can and cannot do

Consumer monitors use a light-scattering sensor, which counts particles by how they scatter a laser beam. They are useful for trends and comparisons, such as "the kitchen is worse when I fry" or "the purifier lowered levels", but they are not precise. Limits include:

• They can over- or under-read in humid air, because water droplets are counted as particles.
• Different devices disagree with each other and with official stations.
• TVOC and formaldehyde sensors are rough and may respond to many things.
• CO2 sensors vary; some use a reliable method and others estimate it from other gases, which is not accurate. Look for a monitor that states it measures CO2 directly.
• They do not detect everything, and a "good" reading does not prove the air is safe.
• Placement affects readings.

Treat any single number with caution and look for patterns. Compare with outdoor AQI from official sources for context.

Choosing a monitor

• PM2.5 and PM10 at minimum, with a clear display and a traffic-light colour scale for easy reading by older eyes.
• CO2 and humidity for ventilation and damp.
• Large screen, adjustable brightness, no confusing menus.
• Power: a rechargeable battery that lasts, or mains with a cable that does not trail across the floor; handle power cuts by keeping it charged.
• Alerts that can be silenced.
• App connection is optional; useful for a relative far away; see health devices for a parent far away.
• Brand and support: a maker that states what its sensors measure and offers support and replacement.
• Budget: costs vary widely; a mid-priced PM2.5 and CO2 monitor is usually enough. See health device budgets and quality checks in India.

Where to place it

• At breathing height in the room where your parent spends the most time, usually the bedroom or sitting room.
• Away from kitchens, windows and doors, air conditioner vents, fans, purifiers and direct sun.
• On a stable surface, not in a corner or behind furniture.
• For comparison, place a second monitor, or move the same one, between rooms to see where air is worst.
• Run it for at least a day to see the day and night pattern, and then occasionally.

Using the readings

When PM2.5 or AQI is high indoors:

• Check for sources: frying, incense, mosquito coils, agarbatti, wood or coal stoves, smoking, dust from sweeping and construction next door.
• Reduce sources. Use exhaust fans or chimneys when cooking, avoid burning coils and incense in the room where your parent sleeps, and clean with a damp cloth rather than dry sweeping.
• Keep windows closed during severe outdoor pollution, especially early morning and evening, and ventilate briefly when outdoor air is better.
• Run an air purifier with a HEPA filter, in a closed room, sized for the room. See air purifiers: choosing one for an older adult's room and air purifier filters: replacement, costs and maintenance.
• Limit outdoor walks on very polluted days. See a pollution season plan for older adults.

When CO2 is high:

• Open a window or door for a few minutes, or use a fan to bring in fresh air, ideally when outdoor air is cleaner.
• Avoid too many people in a small closed room.
• Accept a balance: ventilation can let in outdoor pollution on bad days, so use a purifier and short, timed ventilation.

When humidity is high:

• Use a dehumidifier or ventilation, fix leaks and avoid drying clothes in the bedroom.
• Clean mould safely, avoiding disturbing it near your parent. See indoor air quality for older lungs: dust, smoke and damp.

Linking air quality to health

Bad air does not cause identical symptoms in everyone. People with COPD, asthma, heart failure, previous stroke or heart attack, and frail older adults are more sensitive. Warning signs include more coughing, wheeze, breathlessness, chest tightness, eye or throat irritation, headache and unusual tiredness. If symptoms rise on days of poor air, tell the doctor, and ask for a written action plan; see building a COPD action plan with your doctor. A pulse oximeter can help in people with lung disease, though a normal reading does not rule out a problem; see pulse oximeters: how they work. Masks, if the doctor advises, need to fit well to filter fine particles, and some people with lung disease find them hard to tolerate.

Carbon monoxide: a separate danger

Burning charcoal, wood, kerosene or gas in closed rooms, running a generator indoors or a faulty water heater can produce carbon monoxide, which is invisible and odourless. Symptoms include headache, dizziness, nausea, drowsiness and confusion, and it can be fatal. A pulse oximeter may read falsely normal. If you suspect it, get everyone into fresh air at once and call 112. Use a dedicated CO alarm where fuel is burned indoors, and never use a monitor that does not state it measures CO for this purpose. See also pulse oximeter accuracy.

Care of the monitor

• Keep the air inlet and outlet clean; dust blocks the sensor. Clean with a soft brush or a gentle puff of air, following the maker's instructions.
• Do not place it in steam, water or heavy grease.
• Recalibrate or replace if readings seem stuck, strange or out of line with others. Sensors age over a year or two. See calibration, batteries and replacement of home health devices.
• Keep it charged and away from children.

When to ask a professional

Ask a doctor or chest physician if your parent's breathing worsens on polluted days, and for a personal action plan. Ask a pharmacist about masks and inhalers. Do not rely on a monitor to decide treatment. Call the doctor if symptoms such as breathlessness, wheeze or chest tightness increase. Call 112 for severe breathlessness, chest pain, blue lips, confusion or suspected carbon monoxide poisoning.