A new study found that even if put filters on your doors and windows as protection from outdoor pollution, 25 percent of it can still get indoors.

According to the World Health Organization (WHO), air pollution is the contamination of the indoor or outdoor environment by any irritants that affects the natural, clean air. Common source of air pollution includes household combustion appliances, motor vehicles, factories, and forest fires. Pollutants include carbon monoxide, ozone, nitrogen dioxide, and sulphur dioxide. Exposure to air pollution, whether indoor or outdoor, can cause fatal respiratory and other diseases.

Randy Martin, lead author of the study and a professor of Environmental Engineering, studied how air pollutants affect the quality of the air that we have indoors.

Martin explained that bad particles or pollutants in the air dissolve when heat is applied. This is the reason why red air days are most common during the colder months of the year. This is one of the reasons why the air inside our house is presumed to be safer.

However, the study found out that there are certain pollutants which can still enter the house and affect the quality of the air we breathe even if we are indoors.

“Our study shows the ammonium nitrate volatilizes very quickly once it becomes indoor,” Martin told Fox 13 News.

On the average, indoor air has at least 25 percent of particle pollution compared to outdoor air. However, that percentage varies according to other factors such as the use of air scrubbers, UV lights, or air filters.

On a similar note, a service technician from SameDay Heating and Air noted that the quality of the air indoors is an issue that people should start looking into. Branden Boyton revealed the culprit.

 “It’s an issue with their filtration system.” he told Fox 13.

The quality of air indoors may be influenced by air filters but homeowners should make sure that they have the right kind of air filter. Homeowners should look for the Minimum Efficiency Reporting Value rating. The higher the rating is, the cleaner the indoor air will be.