According to the World Health Organization, the air inside our homes can be several times more polluted than the air outside. It’s a paradox. We treat home as a shelter from smog, while in fact we breathe a mixture of dust, carbon dioxide, volatile organic compounds released by furniture and cleaning products, and humidity that feeds mould. We inhale most of this air during sleep, when the body regenerates and is most vulnerable. Discover what really degrades the air inside four walls and how to improve the air quality at home without expensive devices.

Key facts about indoor air quality:

We spend 90 percent of our time indoors, mostly at home and in the office
VOCs, dust and mould are the three biggest threats inside our homes
A PM2.5 and CO2 sensor gives an objective answer to whether the air at home is healthy
Cross-ventilation three to four times a day for five minutes refreshes the air better than a tilted window left open for an hour
An air purifier with a HEPA filter reduces particulate matter, but it doesn’t replace ventilation

Why does indoor air quality matter so much for health?

The air we breathe at home reaches the lungs around 22,000 times a day and directly affects the respiratory, cardiovascular and nervous systems. Fine PM2.5 particles enter the bloodstream and raise the risk of heart disease, stroke and cognitive decline. Indoor pollutants accumulate faster than those outside, because there’s no wind or rain to cleanse the atmosphere.

The effects of poor air are surprisingly mundane. Headaches, dry eyes, a blocked nose, weaker concentration, worse sleep. Over the long term, the risk of asthma, allergies and chronic respiratory diseases grows. Research led by Joseph Allen at the Harvard T.H. Chan School of Public Health found that improving air quality in office spaces lifted cognitive test scores by as much as 61 percent compared with standard conditions (2016). A home behaves in the same way.

How much time do we spend indoors?

Statistically, we spend around 90 percent of every day indoors. At home, in the office, in cars, in shops. The US Environmental Protection Agency has confirmed this figure for decades and treats indoor air as one of the main routes of exposure to chemical pollutants. In practice, the air in your bedroom and kitchen affects your health more than the smog outside the window.

How to check and test the air quality at home?

The simplest method is a home sensor that measures PM2.5, PM10, carbon dioxide and volatile organic compounds. These devices cost from a couple of hundred zlotys and display real-time results, so you can see immediately when cooking, a scented candle or a lack of ventilation pushes pollution levels up. Without measurements, we’re acting blind.

What’s worth checking first:

PM2.5 and PM10 – particulate matter from cooking, candles and outdoor smog
CO2 – rises rapidly in a bedroom with closed windows and signals a lack of fresh air
Relative humidity – above 60 percent encourages mould, below 30 percent dries out mucous membranes
Volatile organic compounds (VOCs) – released by furniture, paints, perfumes and cleaning products
Radon – an odourless gas from the ground; in some regions of Poland a one-off test is worth doing

What should the air quality at home look like?

Four parameters kept within recommended ranges are crucial for health. PM2.5 should remain below 15 µg/m³ as a daily average. In line with the WHO guidelines from 2021. CO2 levels are best kept below 1,000 ppm. Above that figure concentration drops and sleep quality declines. Relative humidity in the 40 to 60 percent range limits the growth of mould and dust mites.

Temperature plays a smaller direct role in health, but it influences the other parameters. In rooms that are too warm and humid, mould grows faster. In spaces that are too dry and overheated, dust from textiles is more easily airborne. The bedroom, it’s worth keeping 18 to 20 degrees and humidity around 50 percent.

What are the symptoms of poor indoor air quality?

The first sign is a set of complaints that appear at home and ease after going outside. Dry eyes, an irritated throat, a morning cough, frequent headaches, fatigue after a night’s sleep. These are classic symptoms of excess CO2, dust or VOCs. They’re often confused with allergies or chronic exhaustion.

Signals worth taking seriously:

Mould in the bathroom or bedroom – black spots on grout, corners and windows
Breathlessness and a cough that worsen in the evening or after the night
Frequent upper respiratory infections in the household
A musty or chemical smell that lingers despite cleaning
Worse sleep and concentration with no other obvious cause

What are the biggest indoor air pollutants?

The most harmful are particulate matter PM2.5 and PM10 and volatile organic compounds, also known as VOCs. PM2.5 is created during cooking, frying, burning wood in a fireplace, lighting candles and when smog drifts in from outdoors. VOCs evaporate from new furniture, panels, glues, paints, deodorants, freshly washed laundry and air fresheners. The third source is bioaerosols – mould spores, dust mites and bacteria.

VOCs, mould, dust – which are the most dangerous?

VOCs are particularly hazardous because they’re invisible and don’t always have a smell. While long-term exposure is linked to airway irritation, headaches and a higher risk of chronic disease. Mould releases mycotoxins and spores that trigger allergies, asthma and can affect the nervous system. Dust in small amounts is tolerated, but once it carries mites, hair, synthetic fibres and a layer of fine particles, it becomes a leading trigger of allergies and asthma in children.

How to improve the air quality at home?

The fastest results come from refreshing the air and reducing pollution sources. Cross-ventilation three to four times a day for five to ten minutes exchanges the air in a flat better than a single tilted window left open all day. HEPA filters in air purifiers, regular vacuuming with a HEPA-rated machine, washing bedding at 60 degrees and cutting down on scented candles, incense and aerosol fresheners are also effective.

The second pillar is humidity and ventilation control. Switch on the extractor fan or hood while cooking. Open a window after a shower. Check that ventilation grilles are clear once a year. Daily contact with fresh air outdoors helps reset the respiratory system. The practice of forest bathing shows how surroundings affect the lungs and the nervous system. Small habits stack up into a clear difference after two or three weeks, and lowering exposure to pollutants at home eases the body’s burden while also dampening chronic stress, which amplifies the inflammatory response to airborne irritants.

A 7-step plan for clean air at home

If you’re wondering how to improve the air quality at home without chaos, start with measurement and then add one change a week.

Seven concrete steps:

Buy a sensor measuring PM2.5, CO2 and humidity – it’s your point of reference
Introduce cross-ventilation three to four times a day for five to ten minutes, especially in the morning and before sleep
Use the kitchen hood every time you cook or fry, even if you don’t see smoke
Place a HEPA purifier in the bedroom or living room and match the capacity to the floor area
Throw out scented aerosols and candles, and replace them with ventilation and natural essential oils
Wash bedding at 60 degrees every one to two weeks, and vacuum mattresses and upholstery
Inspect ventilation once a year – clear grilles, the heat-recovery unit and any signs of mould

A diet that supports the body in the face of polluted air is rich in antioxidants. The longevity diet is built around vegetables, fruit and plant fats, which soften the impact of exposure to particulate matter and VOCs.

Clean air at home – 5 rules that make the difference

Start with measurement, ventilate cross-wise three times a day. Switch on the hood while cooking. Place a HEPA purifier in the bedroom and cut down on scented aerosols. Five rules that achieve more than expensive devices used inconsistently. After two weeks, the sensor shows lower readings and sleep improves.

FAQ: Frequently asked questions about indoor air quality

Does an air purifier really work?

An air purifier with a HEPA filter and an adequate CADR rating reduces PM2.5 in a room by 70 to 80 percent. But it doesn’t remove CO2 or most VOCs, so it doesn’t replace ventilation.

Which plants clean the air at home?

Plants such as peace lily, snake plant or spider plant absorb a fraction of pollutants. But their real effect on air quality in a flat is small. They improve mood and humidity, but they don’t replace ventilation.

Is ventilation enough to improve air quality?

Cross-ventilation three to four times a day for five to ten minutes refreshes the air and lowers CO2, but with outdoor smog or strong indoor VOC sources it’s worth combining it with an air purifier.

How often should ventilation filters be replaced?

Filters in heat-recovery units and air purifiers are usually changed every 6 to 12 months, while in flats next to busy roads or after a renovation – every 3 to 6 months, in line with the manufacturer’s recommendation.

References:

Klepeis, N. E., et al. (2001). The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. Journal of Exposure Analysis and Environmental Epidemiology. https://doi.org/10.1038/sj.jea.7500165