With the colder months approaching, many of us will spend the majority of our time indoors. But, the indoor air we breathe is often more polluted than the air outdoors.

So when opening windows for fresh air is not an option, air duct cleaning can be an important home-winterizing approach to keep clean air circulating during these next couple of months.

Though no study has proven contaminated air ducts cause health problems, air ducts filled with dust, pollen, animal dander and microbes can circulate these harmful spores throughout your home or office, contributing to allergies or illness.

What’s more, air duct cleaning has been shown by NADCA (National Air Duct Cleaning Association) to improve efficiency and, therefore, heating savings, by 10-30 percent. Dirt — the No. 1 cause for failing heating systems — not only absorbs heat, but also restricts airflow.

To determine whether or not your air ducts need cleaning, check out the Environmental Protection Agency’s (EPA) checklist.

Once you’ve detected a contaminated system — you’ve inspected your air duct for visible spores, mold and dust — what should you look for in an air duct cleaning company?

First, be sure to evaluate their process. Proper cleaning services should include cleaning of all registers, the interior of the ducting, the furnace fan and the interior of the heating and ventilating system. It is extremely important that all components are properly cleaned or else the entire system can be exposed to recontamination.

Then, be sure the company uses a high-efficiency filtration system, such as HEPA, to protect your carpet and furniture from the extracted contaminants.

Lastly, to be sure your air duct received proper cleaning, review the EPA’s Post Cleaning Consumer Checklist