Air Quality and Ventilation Indoors

Learning about ventilation and indoor air quality is an important step in mastering your home and making it a safer, healthier and more comfortable place to live.

Consider this information for replacing polluted air indoors with fresh air.

According to the U.S. Environmental Protection Agency[1], typical indoor air quality can be four to five times more polluted than outdoor air quality. In order to achieve and maintain a healthy indoor atmosphere in the home, it is critical to be constant in removing polluted air and introducing fresh air cyclically.

Air Pollution Indoors

The air in a home can have any number of pollution sources. These can include:

Outdoor pollutants that can enter the home as well as air pollution moving through a home's HVAC system[2] can create a build-up of bacteria, pollen, mold spores and dust. In humid climates, humidity levels may cause the growth of mildew or create excessive condensation problems.

The more airtight the home, despite its good energy-efficiency, the more prone they are to have poorer indoor air quality. This is because polluted air cannot escape while fresh air is not introduced.

Improving Indoor Air Quality

Here are some ventilation options that can help to improve the quality of indoor air:

Air Conditioning

Using air conditioning units to reduce humidity and cycle air through a home works well at removing contaminants, especially those localized in the bathroom and kitchen.

However, they do not all introduce fresh air and they have a tendency to depressurize the home. This can draw unconditioned outdoor air into the home through cracks around doors and windows, introducing unwanted pollutants from outside as well as causing back-drafting of any unsealed combustion appliances.

Semi-Controlled Ventilation

This venting system would include a return duct to allow outdoor air to connect with the central air return plus an exhaust fan. This can help in the removal if indoor pollutants.

Using this approach, it is important to ensure all ducts are sealed to prevent the ingress of unwanted toxic fumes into the return ducts, causing toxins to be circulated throughout the home. This point is more especially true in a basement, where such substances as coal, paint, solvents, fertilizer and other household chemicals are generally stored.

Advanced Ventilation Options

By far the most effective type of home ventilation is a mechanical, fully ducted, whole-house system. This will provide a steady supply of freshly cycled, filtered and conditioned air from outdoors while it exhausts stale interior air.

In this case, the pressure inside the home will remain balanced because the same volume of air is drawn in as is exhausted out. This helps to prevent back-drafting of any combustion appliances while providing a better quality of interior air.

Mechanical Ventilation

There are mechanical ventilation systems that can be set to automatically maintain an air exchange rate generally recommended to maintain good air quality of 0.35 air changes per hour.

There are many sizes and configurations of this type of mechanical ventilation available. The best, most robust system will include air filtering, pre-conditioning and also booster fans.


Here's a look at each feature of this type of system:


A drawback to installing this type of mechanical ventilation is high upfront costs. These come from more complex installation and additional equipment.

Homeowners should be aware of the additional mechanical complexities involved with these systems, as well as being responsible for maintenance.


The air we breathe in our homes should be as clean and healthy as we can make it with whatever appliances or equipment we have at our disposal.

Air filters, air purifiers, air conditioning systems and ventilation systems all play a part in helping to clean and detoxify our breathable air in the home.

Further Reading

There is more information on this subject that can be found in the titles of articles in this category of the website as listed below: