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The ultimate guide to indoor air quality and air pollution

Can technology help tackle air quality

In this ultimate guide to indoor air quality and air pollution we explain:

  1. What is air pollution and pollutants?
  2. Is indoor air quality worse than outdoor?
  3. How does indoor air quality impact our health?
  4. How to measure indoor air quality
  5. How contaminants get into your home
  6. How to improve indoor air quality
  7. What plants improve indoor air quality

1: What is air pollution and pollutants?

Pollutant: a substance that pollutes something, especially water or the atmosphere.

When we talk about pollutants, we may think about them being outdoors in the air, ground or in our water. In the case of air – some of us may overlook the fact that unless we manage it, the pollutants in our homes will be the same as those in the outside air.

2: Is indoor air quality worse than outdoor?

Indoor air pollution can be up to 10 times worse than outdoor air pollution. This is due to the fact that enclosed internal spaces allow pollutants to build up more compared to external, open spaces.

When it comes to our health and wellbeing, the quality of the air we breathe is important. We spend over 90% of our time indoors and most of that is in our homes. And if you think your home is safe from air pollution, you might want to think again.

Air pollutants of current interest among researchers include:

  • ozone
  • nitrogen oxides
  • VOCs
  • bioaerosols

3: How does indoor air quality affect our health?

The Lancet Commission on Pollution and Health has declared pollution as the greatest health risk to the world population, of which air pollution is by far the greatest contributor.

Source: Landrigan PJ, Fuller R, Acosta NJR, et al. The Lancet Commission on pollution and health. Lancet. 2018; 391: 462-512.

Air pollutants and poor indoor air quality can have a very real threat to our health.
The severity of the potential health effects from indoor air quality depends on a few things:

  • how polluted your indoor air is, and
  • the length of time of exposure.

Symptoms shown following exposure to indoor air pollution can range from:

  • coughing
  • sneezing
  • watery eyes
  • fatigue
  • dizziness
  • headaches, and
  • upper respiratory congestion.

Over the short term these symptoms don't sound too serious. Longer term however, these could have a serious effect on your health.

Long-term effects can include:

  • weight gain
  • depression
  • allergies
  • autoimmune disease
  • cardiovascular disease, or
  • even asthma.

Weight Gain

Have you been putting on weight but can’t understand why? Could indoor air pollution play a role in this unexplained weight gain? Yes, it is possible that polluted indoor air could be a factor.

A study, published in the Journal of the Federation of American Societies for Experimental Biology, observed two groups of rats. Both groups ate the same food. One group had clean air, the other polluted. The group of rats that had the more polluted air gained more weight than the group with clean, filtered air. The implication is that the same could be true for humans. Other studies seem to support this conclusion.

Source: Forbes: Will Air Pollution Lead to Weight Gain

Did you know that noise pollution has also been linked to obesity?


Depression can be a debilitating health condition. The World Health Organization consider it to be a lead cause of disability worldwide. The cause of depression can be genetic or a build-up of stress. Find out more about what causes stress here.

Have you considered that the air you breathe could also contribute to depression?

Whilst there are many causes of depression, there is potential evidence that long-term exposure to air pollution can magnify the intensity of the symptoms. Although there is an acknowledgement that more research is needed.


An estimated 4.2 million deaths, globally, are linked to ambient air pollution, mainly from:

  • heart disease
  • stroke
  • chronic obstructive pulmonary disease
  • lung cancer, and
  • acute respiratory infections in children.

In the UK

  • 5.4 million people are currently receiving treatment for asthma
  • The UK has some of the highest asthma rates in Europe and on average three people a day die from asthma.
  • In 2016 (the most recent data available), 1,410 people died from asthma.
  • The NHS spends around one billion a year treating and caring for people with asthma.


  • It’s estimated that 334 million people have asthma
  • 14% of the world’s children experience asthma symptoms
  • 8.6% of young adults (aged 18-45) experience asthma symptoms
  • 4.5% of young adults have been diagnosed with asthma and/or are taking treatment for asthma.

Could this increase in asthma be the result of poor indoor air quality? Asthma is a respiratory disease and can be impacted by poor indoor air quality. Pollutants are small particles that find their way into the air. They pollute the air you breathe which can then lead to potential respiratory issues.

Indoor air pollutants and allergens play a major role in triggering asthma attacks. They also trigger asthma symptoms or make a person’s asthma worse in general.


An allergen is a type of toxin, or other foreign substance, that produces a physical response - the body's immune system defends a perceived threat that would otherwise be harmless. We call this reaction “allergies”.

Allergens can be transported by the air. An allergy to pollen – which is carried in the air – is common. There's a strong chance that we all know somebody who has hay fever; you might even suffer yourself.

Pollen and other pollutants in your home’s air can trigger the onset of allergy symptoms such as:

  • skin rash
  • headaches
  • sneezing
  • runny nose
  • swelling, and
  • fatigue.

As the temperature falls in the winter, we tend to stay indoors more. As a consequence, allergens can increase as air pollutants build-up in your home’s air. Your home can contain indoor air pollutants from household items such as cleaning products, as well as outdoor allergens.

A good Mechanical Ventilation Heat Recovery (MVHR) system with efficient filters can help. Read more about this here 

Selecting cleaning materials based on their ingredients can also be beneficial.

Autoimmune Diseases

Autoimmune diseases: an immune system response which leads to the destruction of the body’s own tissues and organs.

Awareness of autoimmune disease is growing as increasing numbers of people are being diagnosed with these debilitating diseases.

A Canadian study suggests that the increase in diagnoses of autoimmune diseases can be linked to air pollution. While another found that one category of particulate matter, diesel exhaust nanoparticles, showed to have an inflammatory response on the cells of those who suffer from systematic autoimmune rheumatic disease

Cardiovascular Disease

Cardiovascular disease is the cause of thousands of deaths in the UK. Every year:

  • 160,000 people die from heart and circulatory disease
  • 73,000 people die from coronary heart disease
  • 40,000 people died from a stroke
  • 42,000 people died prematurely from cardiovascular disease.

Indoor air quality could be one of the contributing factors to cardiovascular disease.

Research, in America, has studied the possible link between air pollution and heart health, finding that when you breathe in, pollutants can affect your cardiovascular system.

Pollution particles smaller than 2.5 microns are the main cause for concern, according to researchers. Due to the fine size of these particles they are more easily digested by the human body, which than can lead to irritation of the lungs and blood vessels around the heart.

Further reading: http://www.heart.org/ and https://www.lung.org/   

4: How to measure indoor air quality

To measure indoor air quality, you will need a special tool called a VOC Meter which can measure Volatile Organic Compounds.

How Do VOC Meters Work?

When air enters the VOC meter, a UV light interacts with the molecules in the air. Organic compounds release charged ions when they pass through the light. These are then captured by a negatively charged plate producing a measurable electrical current. The electrical current is measured and used by the VOC sensor to determine the type and quantity of the detected VOCs. The higher the electrical current, the more pollutants in the air. The UV lamp used in the VOC meter determines what contaminants can be detected by the VOC sensor.

You can also use a carbon dioxide (CO2) meter. The problem with these is that although they track the CO2, they don’t detect any other dangerous chemicals. You should also consider having a radon detector and a carbon monoxide detector in your home.

Interpreting the Results

Most of the devices available for home use are good for spotting trends. For example, if you notice that when you clean there's a spike in air pollutants inside, you know to look at the products being used and swap for alternative cleaning products that don’t release as many pollutants.

5: How contaminants get into your home

Indoor air can contain many pollutants including:

  • pollen
  • dust
  • minute scales from hair, feathers, or skin that may be allergenic
  • cleaning solvents
  • formaldehyde
  • fungi
  • viruses, and much more.

These tiny particles, some too small to see, make their way into your home’s air and into your lungs. Particles like dirt, dust, and pollen enter your home through open windows, doors, cracks, and chimneys. Bacteria and mould find their way into your home and reproduce to stay alive.

Pets are a common allergen source that cause bad indoor air quality from their hair, skin and saliva. Other sources of contaminants include perfume, cleaning products, paints, and cooking fumes.

Poor Ventilation

Without proper ventilation, indoor air cannot circulate and becomes stale and stagnant. This means all the contaminants floating around indoors have no way to escape. This causes allergic reactions, discomfort, and other health concerns.

High Humidity

Too much moisture in the air also creates an issue with indoor air quality. High humidity allows dust mites, mould, mildew, viruses and bacteria to breed. These tiny contaminants get released into the air and then into your lungs. High humidity can also promote household materials to release chemicals such as formaldehyde into the air as a vapour. Formaldehyde is a colourless, strong-smelling gas and is a strong irritant that affects the eyes, nose, throat, and skin.

6: How to improve indoor air quality

As the above information explains, air pollution can be a real risk – but there are ways you can improve indoor air quality.

Keep your floors fresh

Vacuum. Chemicals and allergens can accumulate in household dust for decades. By using a vacuum with a HEPA filter you can reduce concentrations of lead in your home. You can also get rid of other toxins and allergens. Using a vacuum cleaner with strong suction, rotating brushes, and a HEPA filter ensures that dust and dirt won’t get blown back out in the exhaust. In high traffic areas, vacuum the same spot several times. Don't forget walls, carpet edges, and upholstered furniture, where dust accumulates. For best results, vacuum two or more times each week and wash out your filter.

Mop. Mopping picks up the dust that vacuuming leaves behind. Use plain water to capture any lingering dust or allergens. Consider a microfiber mop as they collect more dust and dirt than traditional fibres.

Mats. Put a large floor mat at every external door. People traipse all sorts of chemicals inside via the dirt on their shoes. A door mat will reduce dirt, pesticides, and other pollutants from getting into your home. To best protect your family, ask visitors to remove their shoes when entering your home. Keep house shoes, slippers, and socks near the door.

Keep a healthy level of humidity

Dust mites and mould love moisture. Keeping humidity around 30%-50% helps keep them and other allergens under control. To manage humidity at home you can also:

  • Use mechanical vent or open a window when cooking, running the dishwasher or bathing
  • Don't overwater houseplants
  • Vent the tumble dryer to outside
  • Fix leaky plumbing to prevent moisture-loving mould.

Make your home a no-smoking zone

Cigarette smoke contains more than 4,000 chemicals. Research shows that second-hand smoke increases a child's risk of developing ear and respiratory infections, asthma and cancer. For the smoker, this addiction causes cancer, breathing problems, heart attacks, and stroke.

Test for radon

Whether you have a new or old home, you could have radon – which is a radioactive gas. This colourless, odourless gas raises the risk of lung cancer and comes from the natural decay of uranium found in soils. Testing is easy, inexpensive, and takes only a few minutes. If you discover a radon problem, there are simple ways to reduce levels of the gas that are not too costly.

Use natural air-fresheners. Do you associate that lemony or pine scent with a clean kitchen or clean clothes?

Did you know, synthetic fragrances in laundry products and air fresheners can emit dozens of different chemicals into the air. So what can you do?

  • Look for fragrance-free or naturally-scented laundry products
  • Switch to mild cleaners that don't include artificial fragrances
  • Stop using aerosol sprays - deodorants, hair sprays, carpet cleaners, furniture polish, and air fresheners
  • Let in fresh air. Open windows so toxic chemicals don't build up in your home
  • Use sliced lemons and baking soda to get a clean scent in the kitchen
  • Bring nature indoors. Any room is prettier with a plant. NASA research shows that indoor plants act as living air purifiers - the foliage and roots work in tandem to absorb chemical pollutants released by synthetic materials

7: What plants improve indoor air quality?

Plants are a great way to improve the air quality inside your home. These top ten indoor houseplants were analysed by NASA in 1989. NASA found that each had a unique way to cleanse the air of toxins. Read the full report from NASA here.

1. Spathiphyllum (Peace Lily)
An evergreen perennial with erect, lance-shaped, glossy dark green leaves, and ovate white flowering spathes to 15cm in length, each with a slender cream spadix within. NASA’s analysis of indoor houseplants revealed that the Peace Lily was the most efficient at removing airborne Volatile Organic Compounds, including formaldehyde, trichloroethylene and benzene.

2. Chrysanthemum morifolium (Florist’s Chrysanthemum)
Chrysanthemum morifolium (also known as florist's daisy and hardy garden mum) is a species of perennial plant from Asteraceae family. These blooms not only help brighten the room, they also help cleanse the air of many chemicals that are common in homes. These include formaldehyde, xylene, ammonia, benzene, toluene, and trichloroethylene.

3. Epipremnum aureum (Devil’s Ivy)
Epipremnum aureum is a species of flowering plant in the family of Araceae. The plant has a multitude of common names including golden pothos, Ceylon creeper, hunter's robe, ivy arum, money plant, silver vine, Solomon Islands ivy and taro vine. It is sometimes called devil's vine or devil's ivy because it is almost impossible to kill and it stays green even when kept in the dark. The most important benefit of Epipremnum aureum is that it is quite efficient at cleansing the air of pollutants, such as benzene, trichloroethylene, xylene and formaldehyde.

4. Dracaena reflexa (Red-Edged Dracaena)
Dracaena reflexa (commonly called song of India) is a tree native to Mozambique, Madagascar, Mauritius, and other nearby islands of the Indian Ocean. It is widely grown as an ornamental plant and houseplant, valued for its richly coloured, evergreen leaves, and thick, irregular stems. According to the NASA Clean Air Study, Dracaena reflexa is one of the most efficient plants at removing formaldehyde from the air in your home, as well as other VOCs, including benzene, trichloroethylene, and xylene.

5. Sansevieria trifasciata (Snake Plant)
Sansevieria trifasciata is a species of flowering plant in the family Asparagaceae, native to tropical West Africa from Nigeria, east to the Congo. It is most commonly known as the snake plant, mother-in-law's tongue, and viper's bowstring hemp, among other names.
According to NASA, it is one of the best houseplants for absorbing airborne toxins, including formaldehyde, nitrogen oxide, benzene, xylene and trichloroethylene.

6. Rhapis excelsa (Lady Palm)
Rhapis excelsa, also known as broadleaf lady palm or bamboo palm, is a species of fan palm (Arecaceae subfamily Coryphoideae, tribe Corypheae) in the genus Rhapis, thought to be native to southern China and Taiwan. It is not known in the wild; all known plants come from cultivated groups in China. The NASA Clean Air Study discovered Rhapis excelsa to be one of the best houseplants at cleansing the air of formaldehyde, ammonia, xylene and toluene.

7. Anthurium andraeanum (Flamingo Lily)
Anthurium andraeanum is a flowering plant species in the Araceae family. It’s most characteristic feature as an ornamental is its brightly coloured spathe leaf, and the protruding inflorescence called the spadix. Common names for plants in the Anthurium genus include tailflower, flamingo flower, and laceleaf. Its name comes from the Greek words anthos, meaning flower, and oura, meaning a tail, referring to the spadix.
According to the NASA Clean Air Study, the Flamingo Lily was incredibly effective at removing airborne formaldehyde, ammonia, toluene and xylene in your home or office.

8. Hedera helix (English Ivy)
Hedera helix, the common ivy, English ivy, European ivy, or just ivy, is a species of flowering plant in the family Araliaceae, native to most of Europe and western Asia. According to NASA’s Clean Air Study, English Ivy is effective at cleansing benzene, formaldehyde, xylene and toluene from the air. Additionally, other studies have indicated that English Ivy also helps reduce mould in your home.

9. Gerbera jamesonii (Barberton Daisy)
Gerbera jamesonii is a species of flowering plant in the genus Gerbera. It is indigenous to South Eastern Africa and commonly known as the Barberton daisy, the Transvaal daisy, and as Barbertonse madeliefie in Afrikaans. This may be a wise decision for your indoor air quality, as NASA’s Clean Air Study found that Gerbera jamesonii is effective at cleansing the air of formaldehyde, benzene and trichloroethylene.

10. Ficus benjamina (Weeping Fig)
Ficus benjamina, commonly known as weeping fig, benjamin fig or ficus tree, and often sold in stores as just ficus, is a species of flowering plant in the family Moraceae, native to Asia and Australia. It is the official tree of Bangkok. According to NASA’s Clean Air Study, Ficus benjamina was effective at cleansing airborne formaldehyde, xylene and toluene.

Hopefully this ultimate guide to air pollution and indoor air comfort has given you some useful information about the topic. If you’d like to find out more about what indoor air comfort is and how design, construction and materials can help to improve it, watch this explainer video.

Disclaimer: The sole responsibility for any views expressed lies with the author(s). Any opinions shared do not necessarily represent the views of Saint-Gobain.

Ieuan Compton
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