Source Control

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Christine G. Crocker, Executive Director, Maine Indoor Air Quality Council (Originally published in Green & Healthy Maine Homes Magazine, September 2021)

The ongoing COVID-19 global pandemic has underscored a critical fact that those of us in the building and environmental health industry have known for a long time:  the air indoors can be significantly more polluted than the air outdoors.  Even before the pandemic closed schools and workplaces, indoors–at home–was still the location where we all spent most of our time. And, because exposures to indoor pollutants can be much greater than exposures to outdoor pollutants, the concern for the risks to our health from so much time spent indoors is real.

Two of the primary causes of indoor air quality problems are 1) indoor pollutant sources that release gases or particles into the air, and 2) excessive moisture/humidity levels that can lead to mold and bacterial growth, as well as mechanical/structural systems failures.

The most effective strategy to improve indoor air quality in homes is to practice source control. Source control is the process of eliminating a pollutant at its source, followed by reducing or managing the individual sources of pollution and their emissions. 

How to Implement Source Control in Your Home

Step #1:  Eliminate.

Keeping pollutants out of the indoor environment is the primary means to prevent the risk of exposure to it.  If it isn’t there, it cannot hurt you.  Examples of pollutant elimination in your home can include:

  • Choose furnishings and products with the lowest gas and vapor emissions. Homes today are loaded with furniture, carpeting, and coatings that release chemicals into the indoor air.  Avoid pressed wood products, products with flame and stain retardants, and always use low-VOC paints and finishes.
  • Choose electric or induction cooktops over gas cooktops.
  • Avoid pesticides by practicing more natural pest control techniques.  Stuff copper mesh into foundation cracks to deter mice, use traps instead of chemicals, and keep your home clean and dry to make it less attractive to insects.
  • Switch to more natural cleaning products.  Soap, water, vinegar, and baking soda are excellent options.
  • Go fragrance free.  The scents in laundry detergents, cleaning products, and air fresheners are created by chemicals that may make you sick.
  • Maintain your indoor humidity between 30-50% to prevent mold and bacterial growth indoors.

Step #2:  Reduce and Manage.

Sometimes, completely eliminating a pollutant from the indoor environment just isn’t possible.  Reduce and manage the pollutant source when elimination of the pollutant is not an option.  Examples include:

  • Ventilate! Ventilation provides a pathway for pollutants that find their way indoors to leave your home before they can make you sick. Open windows, use window fans, or install a balanced heat or energy recovery ventilation system to bring fresh air into your home and exhaust out pollutants. Install a properly sized range hood that is vented to the outdoors rather than recirculated indoors. Use properly sized bathroom fans that vent to the outdoors to remove odors and excess moisture from showers and baths.
  • Test the air and water (if you have a well) in your home for radon, and install systems to reduce radon to acceptable levels if needed.
  •  Filter the indoor air to capture dust, pollen, allergens, mold spores, pet dander, smoke, viruses and bacteria, and other small particles
  • Carefully consider the value of a product, appliance or system with the risk of its use
  • Always follow the label instructions for application of all chemical products used indoors
  • Properly store and ventilate hazardous materials, and dispose of unused products to limit exposures
  • Schedule use of contaminants at times when people aren’t around to limit exposure.
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