5 techniques to improve indoor air quality

Indoor air quality refers to the condition of the air inside your home or building. According to the International Energy Agency on Ventilation (AIVC (1)), good indoor air quality is characterised by air that is free from pollutants causing irritation, discomfort, or illness.

A study conducted in Denmark by Professor Jan Sundell (2004) identified four key aspects influenced by indoor air quality (2):

• Comfort: The air’s freshness is immediately noticeable when entering a building.
• Health: Poor air quality can negatively affect respiratory and overall health.
• Performance: High-quality air boosts mental performance and well-being.
• Connection to nature: Fresh air fosters a sense of connection with the outdoors, particularly when accessed through windows.

The quality of the air inside your home (IAQ) is affected by various factors, including ventilation rates, pollution sources, and environmental conditions (3).

An analysis conducted by Navigant Ecofys, featured in the Healthy Homes Barometer (VELUX, 2017) eveals that one in six Europeans lives in unhealthy buildings.

These are homes that are damp, overheated, lack natural light, or suffer from inadequate heating. The study further highlights that Europeans living in damp houses are 1.7 times more likely to report poor health. Similarly, living in homes with insufficient daylight or overheating increases the likelihood of reporting poor health by 1.5 times.

According to a study conducted by Professor Philomena Bluyssen in 2009 (4), indoor air contains numerous compounds that can negatively affect health and comfort. These include:

• Gases (particularly formaldehyde)
• Volatile organic compounds (VOCs)
• Inorganic chemical compounds (e.g., nitrogen oxides (NOx) and sulfur oxides (SOx))
• Particles (such as household dust and combustion by-products)
• Radioactive gases (like radon)
• Biological elements (including mould, fungi, pollen, and dust mites)
• Moisture in the form of water vapour

Bluyssen's study highlights that the majority of these pollutants originate from indoor sources, including:

• Human activities: Tobacco smoke, particles from cooking, and the use of cleaning and personal care products
• Consumer and office electronics: Devices such as laser printers
• Building materials: Thermal insulation, plywood, paint, furniture, and floor and wall coverings

To create a comfortable and healthy indoor space, it is essential to:

• Control pollution at the source: Use building materials and furniture with certified low chemical emissions, opt for low-emission cleaning products, avoid smoking indoors, and manage humidity levels effectively.
• Monitor indoor air quality: Regularly check levels of CO2, humidity, VOCs, and other indoor pollutants.

CO2 levels are a useful indicator of ventilation effectiveness within a space. Since CO2 is produced by human respiration and some household appliances, its build-up can signal inadequate ventilation, which may amplify the effects of other indoor pollutants.

Outdoor air typically contains around 400 ppm of CO2. Indoors, this level rises due to human activity, and concentrations exceeding 950 ppm – as defined by the European standard EN 16798-1 from May 2019indicate poor air quality.

High CO2 levels can lead to symptoms such as drowsiness, headaches, and reduced productivity. Monitoring and managing CO2 levels is especially critical in spaces where people spend extended periods, such as bedrooms, classrooms, and offices.

Natural ventilation is a simple and effective way to lower CO2 levels. By allowing fresh air to enter and circulate, you can dilute and expel accumulated carbon dioxide.

Natural ventilation is essential for maintaining healthy indoor air, and the strategic placement of windows can significantly improve its effectiveness.

Installing roof windows alongside vertical windows enhances air circulation by creating upward air currents. This arrangement allows for better air renewal and the removal of indoor pollutants, such as VOCs and fine particles.

This ventilation method, known as cross ventilation, is particularly effective in rooms with high humidity or pollutant levels, such as kitchens and bathrooms. By combining vertical and roof windows, you can improve the evacuation of indoor contaminants and maintain a healthier living environment.

Exposure to poor indoor air quality can lead to a range of health problems, many of which appear almost immediately. The most common symptoms include:

• Respiratory issues: Irritations in the throat, nose, and eyes, breathing difficulties, and worsening of pre-existing asthma. These are often the first warning signs of deteriorating indoor air quality.
• Allergies: Indoor pollutants like dust mites, mould, and pollen can intensify both seasonal and year-round allergies, causing sneezing, nasal congestion, and itchy eyes or skin.
• General symptoms: Headaches, fatigue, and dizziness are common indicators of exposure to poor indoor air quality. These symptoms can easily be mistaken for those of a cold or flu, making it more challenging to pinpoint the true cause.

Recognising these signs early is essential to address and improve the air quality in your indoor environment.

The effects of prolonged exposure to poor indoor air quality can be severe and may not appear until years later. These consequences include:

• Chronic respiratory conditions: Continuous exposure to pollutants can lead to long-term respiratory diseases such as chronic bronchitis, asthma, or chronic obstructive pulmonary disease (COPD).
• Cardiovascular diseases: Indoor air pollution has been linked to an increased risk of heart disease, high blood pressure, and strokes (CVA), largely due to the chronic inflammation and oxidative stress caused by airborne pollutants.

To mitigate the immediate impacts of poor indoor air quality and minimise long-term risks, consider adopting these five practical measures:

Natural ventilation is one of the simplest and most effective ways to improve the indoor air quality of your home. Regularly open windows, including roof windows, to allow fresh air to circulate and reduce the concentration of indoor pollutants.

Mechanical ventilation systems provide a continuous supply of fresh air while removing stale air. These systems often include filters to remove harmful particles, making them particularly useful in spaces with high pollution levels or in buildings where natural ventilation is insufficient.

Air purifiers equipped with HEPA filters or UV sterilisation technology effectively capture particles, allergens, and microorganisms. These devices are especially beneficial in environments where pollution sources cannot be fully eliminated or in areas with elevated levels of fine particles and allergens.

Reduce pollution at its source by:

• Using materials with low VOC emissions
• Maintaining combustion appliances to prevent harmful gas leaks
• Keeping indoor humidity levels between 40% and 60% to inhibit the growth of mould and dust mites

Maintaining a clean home is essential for reducing indoor air pollutants. This includes regular vacuuming of floors, dusting surfaces, and using non-toxic cleaning and decorating products to minimise harmful chemical residues.