What Affects Indoor Air Quality?

Indoor Air Quality (IAQ) – something that a lot of people, unfortunately, don’t realize the importance of. Since you’re spending most of the time indoors, be it at home, at work, or somewhere else, indoor air quality can significantly affect your health in both the short term and the long term. Since indoor air quality is so important, it’s important to know the factors that affect it.

Indoor Air Quality is affected by several factors, including air pollutants – such as tobacco smoke – in the vicinity, the quality and effectiveness of the indoor ventilation system, the outdoor air climate, and dust particles in the air. 

This article will go on to explore the factors that affect indoor air quality in further detail. I will also provide you with some warning signs of poor indoor air quality and highlight some actionable remedial steps along the way.


First and foremost – arguably the most important factor in determining the quality of air indoors at any place: the pollutants present in the environment. There are numerous air pollutants commonly found indoors.

Tobacco Smoke

A very popular example is tobacco smoke. Not only is it extremely harmful to the person who is smoking, but it also deteriorates air quality and negatively affects the health of other people who happen to be nearby and inhale the smoke – a phenomenon known as ‘passive smoking.’

Read: How To Tell Which Way Air Flows In An AC Unit?


Another better-known category of indoor air pollutants are VOCs (Volatile Organic Compounds). These can commonly be found in chemical products such as paints, cleaning products, insecticides, pesticides, and petroleum-based products, just to name a few. All households tend to have some level of VOCs in their air, but having too much of them can lower the indoor air quality and negatively affect occupant health.

According to the EPA, concentrations of VOCs are up to ten times as much indoors as they are outdoors. 

It can help to use VOC-free products or improve ventilation manually during times when VOCs are expected to be higher (such as during the painting of walls).

Read: Why Does My Central Air Have Two Filters?


All combustion processes and reactions tend to release Carbon dioxide, which typically isn’t harmful and not a cause for concern since it dissipates into the background naturally. 

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However, in cases where there is not enough oxygen, greater quantities of carbon monoxide tend to be released, which is extremely toxic to humans since it binds to the hemoglobin within our red blood cells and prevents the transport of oxygen in the bloodstream.

Exposure for extended durations of time can be fatal. Thankfully, this isn’t something you’ll likely have to worry about.

However, even small quantities of CO2, Carbon monoxide, and similar combustion by-products released into the air can noticeably lower air quality.

You’ll want to be especially careful if you have a fireplace that uses firewood as fuel and is poorly maintained. The chimney has to allow for the efficient escape of the released gasses. 

Take proper care of the equipment in your home that has to do with combustibles, such as your stoves.


Mold is also identified as a common indoor air pollutant. Mold can spread rapidly in areas of your home that are humid, damp, or moist. 

Mold in itself is probably something you don’t want in your house because it can deteriorate the condition of your walls and furniture. But what exactly does it have to do with indoor air quality and health?

If the mold is rampant, there will likely be an increase in the number of spores or tiny fragments of the mold in the air. Inhalation of these fragments can cause health problems, including – in extreme cases – allergic reactions, so their severity is not to be underestimated.

Generally, they will cause problems such as: 

  • Coughing 
  • Congestion 
  • Headaches 
  • Eye irritation 

They can also activate or exacerbate symptoms in people who already suffer from lung and nasal allergies or infections.

To prevent mold from building up in your house, one of the most important steps you can take is monitoring and controlling humidity. Mold needs a moist, damp environment to thrive, and humidity is conducive to said environment.

Aim for a humidity level of 30 – 50 %. A humidifier or dehumidifier are easy and effective ways to control humidity. 

Aside from counteracting the development of mold, keeping humidity at these levels also offers a more comfortable living experience.

Read: Does Air Handler Have Filter?


Another critical component that determines your Indoor Air Quality – Ventilation. Something that you may have noticed while I talked about pollutants is that they usually become a problem when in high, concentrated amounts.

Having an effective and well-functioning ventilation system can help massively with indoor air quality control.

Even in the absence of concentrated pollutants, poorly ventilated homes are often the victims of gradual pollutant and dust buildup. The air becomes stale and unpleasant. It starts containing higher levels of Carbon dioxide and lower levels of oxygen, which can make you feel dizzy and lightheaded. It also becomes a problem if you have asthma.

If your place does not have a ventilation system in place, you want to be careful about keeping all the doors and windows shut all the time, as there may not be another way for fresh air to get in. It can be beneficial to keep your windows open more frequently.

You could also, of course, get a manual or mechanical ventilation system. These will ensure that there is always a constant flux of fresh air in your house and will help remove stale polluted air.

Mechanical ventilation systems typically consist of several vents and ducts located at strategic positions in your house to allow maximum airflow, considering that air tends to flow based on differences in temperature and pressure.

Read: Does HVAC Purify Air?

Other Factors To Consider

Here are some other factors that can affect the air quality in your home, although they usually tend to not be too much of an issue, at least compared to the ones I described above.


By pets, I am referring specifically to pets that shed thin hair in large amounts, such as cats, dogs, and rabbits. Depending on the animal breed and time of the year, these animals can shed a lot of hair. If this hair isn’t combed or brushed off manually, it will end up in the surroundings and, of course, in the air.

This can be a problem, especially if someone in your household is allergic to a certain type of animal, but having too much pet hair in the air will generally result in poorer quality air and slightly poorer quality of breathing and respiration.

You can counteract this by installing air filters or by simply brushing the hair off of your pet on a regular basis.


Having too much dust lying around in your house will lead to more dust in the air which will, in turn, lead to poorer air quality. 

While better ventilation will help here as well, you should be looking to clean and vacuum your living environment regularly. Never let it get too dirty.

Dust can also be brought in from the outdoors, from the shoes of people who enter the house, or from windows when the wind picks up and brings dust with it. It goes without saying that you should close the windows in the event of dusty or sandy winds.

Getting a welcome mat can give the entrance of your house a nice look, while also reducing the amount of dust and dirt brought in. 

Read: How To Reduce Dust With Forced Air Heat?

The Long Term Effects of Poor Indoor Air Quality

While the short-term effects of poor indoor air quality were mostly described above and are generally well-known by people, the long-term effects often go unnoticed or are miscategorized.

While the research on the long-term effects of poor indoor air quality is rather limited, it is suspected that repeated or long-term exposure to poor indoor air quality can result in damaging health complications, such as respiratory diseases and cancer.

Final Thoughts

Indoor air quality can have a major impact on our health simply because of how much of our time we actually spend indoors. Therefore, it is important to be aware of what can cause changes in the quality of indoor air.

Pollutants are largely responsible for decreases in indoor air quality. Some of the most common air pollutants that can be found in residential homes are tobacco smoke, VOCs, combustion gasses and by-products, and mold. Poor ventilation can further decline IAQ, so it’s important to have your house well-ventilated.