Indoor air pollution – Causes, effects and solution (2022)


Outdoor air pollution is widely talked about today. Especially in places like Bangkok and London where people literally see a cloud of smog on the worst of days. But what’s less obvious, but just as dangerous, is the invisible indoor air pollution that exists in every home around the globe. 


Indoor air pollution exists mainly of volatile organic compounds (VOC), extensive Co2, mold as well as particulate matter (PM). The latter one comes from outside through opened windows and cracks in the building, and it then multiplies with the former ones. It is, with this information, suddenly obvious that the indoor air often is more polluted than the outside air. 


Are you now confused about what volatile organic compounds (VOC), extensive Co2, mold and particulate matter is and how it affects us? Don’t worry, that’s why we’re here. So in this article we’ll go in depth into what all of this is, as well as bring you the effects of these contaminants and the solution to the IAQ problem. 


Note: Jump to the summary session if you don’t have time to read the whole article. And if you read the whole article, you can jump from the summary section to the conclusion section since this will otherwise get double information. 


What causes indoor air pollution? And what effects does it have? 

We just touched on the main components of indoor pollution and we’ll now go in depth on each of these, as well as the effects they have on our human bodies. 


  • Particulate matter (PM)

When speaking about pollution people mostly speak of particulate matter. This makes sense because it’s the main contributing factor to outdoor pollution, but there are many more factors that contribute to indoor air pollution and we’ll cover these later. 


In the context of indoor air pollution particulate matter stems from outside of the home. It creeps in via cracks in buildings, poorly filtered ventilation systems or simply when we open our windows. It primarily stems from cars, trucks, buses and every operation that involves the burning of fuels such as wood, heating oil, coil and natural sources such as forests or when farmers in Thailand burn their rice straws. 


Particulate matter has different sizes and we mainly organize it in the categories of PM10 and PM2.5. PM10 is the larger one and it’s generally 10 micrometers in size whilst PM2.5 is 2.5 micrometers in size. To put these sizes in perspective, the average hair size of a human is 70 micrometers, so both PM sizes are completely invisible to the human eye. 


The dangers of these particles is just this. They are tiny enough to travel deeply into our respiratory system and reach our lungs. On their way down there they cause short term effects like irritation in the nose, throat and eyes, as well as shortness of breath and coughing. Multiple studies also show PM can possibly lead to asthma, lung cancer and heart disease. 


So. How do we solve this problem and lower the PM levels of our homes? 


If we live in a polluted area like Bangkok or London, the absolut first thing we need to do is to close the windows since this will stop the majority PM intake. But the second this is done there’s immediately no ventilation at all. This simply means that there is no fresh air coming into the building, and the used air is not leaving the building. This will therefore now lead to a number of other indoor pollutants to grow inside of the building, such as extensive Co2 and mold. It’s because of this of highest priority that some kind of ventilation system is installed.


  • Extensive Co2 (Carbon Dioxide) 

Us humans breathe in oxygen and out carbon dioxide. There is obviously nothing bad at all with this since it’s how nature intended it to be. But ever since we started making airtight houses the norm, we’ve basically mass manufactured buildings without a natural airflow. This means that the air we breathe out (Co2) doesn’t get replaced by oxygen, and we are therefore affected by extensive Co2. 


You have most likely experienced the consequences of this many times in your life. Some of the consequences of this can be that we feel tired, get brain fog, headaches, itchy eyes, itchy noses, dizziness, memory lapses, frequent colds and more. This is generally an impediment in day to day life, but it’s of especial cost if you experience these problems in a business environment because then many thousands are lost every day. 


So, how do we solve the problem of extensive Co2? 


The obvious thing to do here is first of all to open windows. But this will, as recently mentioned, allow PM levels to arrive from outside to get a foot inside your building and this is possibly even worse if you live in a highly polluted area. 


So, what we then need to do is to bring in fresh air from the outside but filter it before it arrives inside the home. We do this by installing an air handling unit that draws air from outside, and then filters the incoming air. It’s of course of highest importance that the air is highly filtered, and you can check out the best filters in the marketplace here, and read more about them here.  


  • Volatile organic compounds (VOC)

VOC’s are a large group of chemicals that exist in everything from smoking odors, to cosmetics, to cleaning products. There are actually over 10.000 different ordinary household products that contain VOCs. 


All VOCs have high vapor pressure, which means that they evaporate easily when in contact with air molecules. Paint, for example, evaporates VOCs directly when it’s put on a surface and can continue to do so for months depending on its chemical formula. The exact same process happens with, for example, cosmetica , cooking odors and cleaning products. All of these VOC transmitters contribute to the majority of our homes having 7 times VOC compared to the outside. 


The vast majority of us have experienced the short term consequences of VOCs in our life. These are: low energy levels, headaches, dizziness, itchy eyes, itchy nose and impaired mental focus. Whilst the long term effects are as dramatic as cancer, liver and kidney damage and it has also been associated with the development of dementia.  


So, how do we solve the problem of high VOC levels?


We first of all recommend everyone who has experienced any of aboves consequences on a regular basis to consult with your doctor and decrease the products that contain VOCs in your home. It’s important to note that this is especially important for children, elderely, as well as those who have asthma and the people who are extra sensitive to irritation from VOCs.


But since it’s really difficult (if not impossible) to remove all VOCs, it’s of extremely high importance to have exhaust fans where most VOCs are emitted. These should therefore be placed in your kitchen and bathroom, and there should moreover be a mechanical ventilation installed so that VOCs throughout the house constantly get removed. A very effective air purifier can also get the job done. There is, however, other problems with air purifiers that you can read about here.


  • Mold and mildew 

Mold and mildew are fungi that are created by moisture in stagnant air. This leads mold and mildew to commonly grow in places like bathrooms, kitchens, laundry rooms, as well as under carpets and wallpapers. It’s very common that mold affects common peoples homes, especially in humid countries, and it’s incredibly common that it affects hotels. Partly due to their often poor ventilation, and also partly due to often having carpeted floors since these contain moisture. 


Mold and mildew are easily noticeable thanks to their rotten kind of smell. This can be seen as a positive since we atleast notice this pollution with our senses and stop then it from affecting our indoor air quality massively. But the big problem here is that mold keeps on coming back if we don’t have a proper ventilation system, since it will always grow in moist and stagnant air.


The health consequences from constant mold and mildew pollution on the human body ranges from everywhere from nothing to serious damages. Nothing means that some people aren’t affected by mold at all, whilst others experience allergic effects such as irritating eyes, nose, skin and throats and others more severe health consequences like fever, profound fatigue, coughing and shortness of breath.  


So. How do we solve the problem of mold and mildew? 


We should first and foremost inspect our whole building and see if there is mold or mildew growing in any area of the house. We should secondly take time ourselves or hire someone to clean it up, and note that it’s really important to be using gloves and eye protection as this can affect your health poorly. 


This does, however, not solve this problem forever since the mold will grow back soon again. So to make sure that mold never grows back, we need to keep the air slightly moving and lower the humidity in the areas that mold has been growing. The former is done by installing an ongoing mechanical HVAC system, whilst the ladder is done by installing exhaust fans in the highly affected areas, as well as possibly installing a dehumidifier. 



Indoor air pollution is caused by outside pollutants as well as pollutants that grow from inside of the home. We went through how particulate matter (PM) comes into our building when we open windows, how this is particularly bad in areas that are heavily polluted and how the  solution is to have closed windows. 


This will however lead indoor pollutants such as mold, VOCs and Co2 to grow since the building now has absolutely no ventilation and therefore highly stagnant air. An air handling with a connection to a high quality filter must therefore be installed so the building can get fresh air from outside but with as few pollutants as possible.  


The other pollutants we went through all grow from inside and these are: 

  • Extensive Co2 
  • Volatile organic compounds (VOC) 
  • Mold and mildew. 


All of these are partly caused thanks to a poor airflow inside of the house, and the basis of the solution is to install a HVAC system so that air keeps moving in and out of the building at a stable pace. 


The effect of these ranges everywhere from, comparitibly, mild allergic reactions such as itchy eyes, nose and skin, to severe health issues such as incredible fatigue, heart and lung disease, asthma and lung cancer. It’s therefore very important to remove as many of these pollutants as possible. 


The complete and long term solution to all of these is to install a complete HVAC system with constant airflow so that the system always draws in fresh air and exhausts the pollution. It is, however, sometimes necessary to also add an air purifier if the inside pollution is extremely high, or if someone in the household is extra sensitive. 


Please read the in depth version in any of the pollutants if you wish to learn more.  



We see that the effect of particulate matter coming into our buildings from outside is huge when our homes are already filled with pollution. It’s therefore of vital importance not to allow outside pollution to come in and we do this by closing windows and filling in the cracks in the building.


This will, as you now know, create a multitude of other problems since the air will be completely stagnant. And the only reasonable long term solution is therefore a complete HVAC system that filters the incoming air and exhausts air where it’s most needed. If we’d for example tried to use an air purifier it would only clean up the VOCs, particulate matter and mold particles, but not the extensive Co2. 


You now have the exact information to clean up all of the indoor air pollutants in your home. If any of your questions weren’t answered or if you’d like to get a free guidance call on how your specific house needs to be ventilated – please feel free to contact us via our LINE, Facebook or just contact us through the messenger icon on the bottom left of this website. We’re happy to hear from you. 

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