Indoor Air Quality and Children's Health

Children aren't just small adults when it comes to air pollution exposure. Because their lungs, brains and immune systems are still developing, and because they breathe faster and take in more air relative to their body weight, the same air can affect a child more than it affects an adult in the same room.

Infants, in particular, take in a much larger volume of air relative to their body weight than adults; a resting infant can move up to twice as much air through the lungs, on a body-weight basis, as a resting adult. Lung development also continues well beyond infancy, with the structures involved in gas exchange still forming throughout early childhood. Combined with the fact that children, especially younger ones, spend a large proportion of their time indoors, at home, in nurseries and in classrooms, this adds up to a meaningfully different level of exposure for the same indoor conditions.

The World Health Organization estimates that environmental risks, including indoor and outdoor air pollution, contribute to more than one in four deaths of children under five worldwide, with air pollution linked to a substantial share of childhood respiratory infections globally. These figures reflect a global picture that includes far more severe conditions than most homes in higher-income countries will ever experience, but they illustrate why children's air quality receives particular attention from health authorities.

Closer to home, indoor air quality is one of several recognised triggers for childhood asthma and allergy symptoms. Reducing exposure to indoor allergens and pollutants, alongside appropriate medical treatment, is recognised by paediatric health bodies as an effective way to help manage symptoms in children who already have asthma. Common effects linked to poor indoor air quality in children include coughing, wheezing, congestion, eye and throat irritation, and, less directly, disrupted sleep and reduced concentration.

Not every pollutant matters equally in every home, but a handful come up consistently in research and guidance on children's indoor air quality.

Children spend more time asleep, relative to their day, than adults, which makes bedroom air quality particularly relevant. Bedroom CO₂ tends to build up overnight in a closed room, and research on ventilation and sleep has found links between elevated CO₂, poorer sleep quality and reduced next-day performance on cognitive tasks, patterns that plausibly extend to children, though most of the direct research has focused on adults.

Classroom-based research offers a more direct picture for concentration specifically: studies of school ventilation have found that better classroom air quality and lower CO₂ are associated with improved concentration and academic performance. This is one reason schools and nurseries increasingly pay attention to ventilation rates, and it's a useful reminder that the same principle applies to bedrooms and playrooms at home.

Temperature is one of the most consistent influences on sleep comfort. Overheating can disrupt the body's natural overnight temperature decline, which is part of how sleep is regulated, and a bedroom that is too warm is generally more disruptive to sleep than one that is slightly too cool. Most comfort guidance places bedroom temperature at approximately 18-22°C (64-72°F), somewhat cooler than typical daytime comfort ranges.

Relative humidity affects comfort in several ways. Air that is too dry can leave the throat and nasal passages feeling irritated on waking, while air that is too humid can feel stuffy and encourages both dust mites and mould growth over time, particularly if condensation forms on windows or walls. A practical target for most bedrooms is approximately 40-60% relative humidity, though some guidance uses a slightly lower range of 30-50%.

Humidity is best interpreted alongside temperature and any visible signs of condensation, rather than as a number on its own; a reading of 55% in a warm room can feel very different from the same reading in a cool one. Research reviewing thermal environments and sleep has found that excess heat and high humidity, especially in combination, are associated with reduced slow-wave and REM sleep and increased overnight wakefulness, reinforcing why a cooler, moderately humid bedroom tends to support better rest.

A few practical points are worth keeping in mind for the rooms children spend the most time in. Ventilate bedrooms and nurseries daily where possible, and consider leaving a door or window slightly open overnight when conditions allow, since a closed room with a sleeping child will generally show CO₂ rising through the night.

New furniture, cots, mattresses and freshly decorated nurseries can all contribute to elevated VOCs and formaldehyde in the weeks after purchase or renovation, so ventilating well and, where practical, allowing time for new items to off-gas before extended use is a reasonable precaution. If placing a monitor in a child's room, position it at a typical breathing height for the room's main use, away from direct sources like a radiator, window or the changing table, so it gives a representative reading rather than one skewed by a single nearby influence

Cooking is one of the most significant everyday sources of PM2.5 in most homes, and young children are often nearby during meal preparation. Using an extractor fan during and after cooking, particularly frying or grilling, meaningfully reduces the particles a child is exposed to in the kitchen and surrounding rooms.

Cleaning products, air fresheners, scented candles and new furniture all contribute VOCs, and pets, dust and pollen contribute allergens that can trigger symptoms in sensitive children. None of these need to be eliminated entirely; ventilating during and after use, choosing lower-emission products where practical, and washing bedding and soft toys regularly all help reduce the everyday load without requiring major lifestyle changes.

Most improvements come down to a manageable set of practical actions:

Continuous monitoring is particularly useful for parents because many of the pollutants that matter most for children's health, including CO₂, PM2.5 and formaldehyde, have no smell and often produce no obvious symptoms until exposure has been sustained for some time. A monitor doesn't replace paying attention to how a child seems, but it can reveal patterns that aren't otherwise visible.