Make Each Breath Count: An Introduction to Indoor Air Quality (IAQ)

Published: • Written by: Erik Rosen and Andrew Guido

Many people think about air pollution as an outdoor problem. However, according to the United States Environmental Protection Agency (EPA), indoor air can be 2 to 5 times worse. And now that we’ve been spending so much more time in our homes due to Covid-19, Indoor Air Quality (IAQ) is something we can no longer ignore.

A major culprit for poor IAQ are the building codes which mandate increasingly air-tight homes in pursuit of greater energy efficiency. The unfortunate consequence is that we trap and breathe in formaldehyde and other toxic volatile organic compounds (VOCs).

The image below shows some of the many sources of IAQ contaminants.

Indoor Air Quality Diagram

Image courtesy of

While chemicals have enhanced the quality of our lives, leading to new products we can’t imagine living without, some are simply too dangerous to breathe day in and day out. Even exposure to very low concentrations of chemical contaminants can result in delayed toxic effects. In addition, key hazards to human health of which we should be aware of fall into the following groups:


  • Radon – This odourless, colourless radioactive gas is naturally occurring, and can seep into a home from the basement and bedrock upon which a house is built. It can settle in your lungs, and long-term exposure can lead to lung cancer. All homes should be tested for radon, which is a relatively inexpensive test that can be done for under $100. If you find that you have an unsafe level of radon there are affordable options to reduce the gas concentration in your home. For further information and useful resources see:
  • Formaldehyde – A colourless gas with a pungent odour, this respiratory irritant primarily affects nasal passages, respiration and eyes. It is a known carcinogen and is used in pressed wood products such as particle board, plywood paneling, fiberboard, manufactured wood furniture (including beds and cribs), laminate flooring, and a host of other items found in most homes. The problem with formaldehyde is that it is a volatile organic compound that “off gasses” at room temperature. It’s almost impossible to avoid exposure to formaldehyde as it is used to manufacture many common building materials.
  • Volatile Organic Compounds (VOCs) – These are organic chemicals that have a high vapour pressure with a low boiling point. As well, the rate of VOC evapouration is influenced by temperature and humidity even at comfortable levels. New homes can have VOC levels 10 to 15 times higher than older homes.1 Common VOC gases found in homes include formaldehyde, benzene, ethylene, glycol, methylene, chloride, tetracholorethylene, toluene, and xylene.
  • Short-chain chlorinated paraffin – SCCPs are potential carcinogens that can be used in rubbers, sealants, adhesives, paints, and caulks.
  • Phthalates – These “plasticizers” are used in PVC piping and other plastics to make them more flexible and resilient. They are used in an extraordinary array of products, including wallpaper, carpet backing, flooring, blinds, roof membranes, acoustical ceiling tile, and electrical cord insulation. Phthalates are potential carcinogens, and may affect the development of the male reproductive system.
  • Lead – While this known carcinogen and developmental and reproductive toxin is no longer used in household paint (or gasoline), it can still be used in some building materials, such as metal flashing, roofing, and electrical cable jacketing.
  • Ozone – A molecule made up of three oxygen atoms often referenced as O3. Ozone has a good and bad side. In the upper stratosphere, it forms a protrective shield against solar ultraviolet radiation. On the ground, it’s a pollutant that can damage the lungs and cause respiratory problems in humans and even animals. Even relatively low levels of ozone can cause chest pain, coughing, throat irritation and shortness of breath.


  • Mould – Some species produce mycotoxins (by-products of metabolic processes) that are incredibly dangerous and can have serious health consequences, including neurotoxic effects. It is important to keep relative humidity levels in your home between 35% and 55% to reduce the incidence of upper respiratory infections and to minimize adverse effects on people suffering from asthma or allergies. Several species of bacteria and viruses survive best at low or high, rather than intermediate, humidity.
  • Particulate Matter – Inevitably found in every home, particulate matter includes dust, pet dander, pollens, spores, soot, smoke, liquid droplets, skin cells and cell debris, and insects like mites, which are all potential allergens if not kept under control. It is important to vacuum often. Particulate Matter (PM) is classified at PM10, PM2.5 & PM1.0. based on their size in micrometres (µg). As a visual reference, a human hair is 50 -70µg, dust and mould is less than 10µg and combustion particles can be less than 2.5µg. The smaller the particles the more dangerous they are to our health as they can be lodged deep in our lungs. Before COVID-19 most of the attention was on PM10 and PM2.5. As a result of COVID-19, the focus is now on PM2.5. and PM1.0. and even smaller particles as COVID-19 can attach to these particles and be inhaled.
  • Carbon Dioxide (CO2) – By simply breathing, we affect air quality by reducing the concentration of oxygen and increasing carbon dioxide. This can result in respiratory acidosis. Symptoms include fatigue or drowsiness, confusion, shortness of breath, and headache. The only truly effective way to reduce CO2 is to ventilate the space with fresh air.

Consumer Products

  • Artificial Fragrances – Found in almost all scented products that don’t explicitly advertise their scents are from solely natural sources, artificial fragrances are increasingly indicated in asthma, cancer, and other serious diseases.
  • Cigarette Smoke – So much has been written about this known carcinogen that most people know by now that if they must smoke, they should do so outside.
  • Chlorinated Hydrocarbons – Typically found in solvents, cleansers, aerosol propellants, hobby and craft products and has been detected in drinking water. They can be absorbed by inhalation, or through the skin and gastrointestinal tract, accumulating in the brain, bone marrow and body fat. Acute, short-term health effects can include dizziness, vomiting, fatigue, depression, and loss of consciousness. Chronic exposure can cause a range of symptoms, from dermatitis, to liver and kidney damage.
  • Pest Control Products – Pesticides contain a wide variety of chemicals and their use needs to be carefully monitored. Inadvertent exposure may occur because of contact with building products, surfaces, or household articles with pesticidal preservatives and subsequent release of these into the air. Exposure to pest control products can occur both by inhalation and by absorption through the skin or ingested following contact with foods. The health consequences range from a mild sore throat to death.

It is not our intention to scare you, but to make you aware that potentially harmful chemicals and biolocial matter reside in some surprising places in the home. The cheapest solution for many people that are sensitive to even low levels of these air borne offenders is to ventilate as often as weather permits. For those with the means, you should purchase a HEPA (High Efficiency Particulate Arrestance) filter system that can lower your exposure level. We will cover many of these in greater detail in future posts.

Erik Rosen is a former copywriter, journalist, and medical writer. He is currently the Director of Programs for the Building Biology Institute.

Andrew Guido is the President & Founder of ERTH. He is a Certified Building Biologist and Circadian (Lighting) Wellness Auditor.

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