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Clean air, year round.

The extreme cold offers no choice but to take refuge indoors, which is now the case for many parts of the nation. A frigid arctic freeze arrived in the U.S. last week, plunging temperatures in the Northeast and Midwest to record lows with the cold reaching as far south as Florida. And the cold wave continues—a powerful winter storm will spread from North Florida to New England later this week.

As schools close and many in the Northeast experience heavy snow and blizzard conditions, people will need to stay inside to avoid the freezing temperatures as well as hazardous traveling conditions. Yet, as more time is spent indoors because of the cold, there is another safety consideration to be made: protecting against indoor air pollution.

What cold temperatures mean for indoor air quality

Cold weather conditions mean greater use of fireplaces, gas heaters and other fuel-burning appliances, which can increase the levels of indoor air contaminants like carbon monoxide and wood smoke. These contaminants stay trapped indoors as windows and doors remain shut. This decreased ventilation, plus more time spent indoors, increases exposure to indoor air pollutants.

Higher Carbon Monoxide levels

The greatest concern for indoor air quality during the winter is carbon monoxide (CO) levels–the US Consumer Product Safety Commission says that November, December, January and February are the top months for CO poisoning. As people try to keep warm during these months, their use of gas heaters and fireplaces goes up. Carbon monoxide in homes is found in the fumes generated by fireplaces, furnaces, portable gas generators (often used during power outages) or other fuel-burning appliances. The symptoms of carbon monoxide poisoning according to the Centers for Disease Control and Prevention (CDC) include headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion.

Extreme cold and snow conditions cause dangerous travel conditions and prevent vehicle use. However, if car travel is needed, it is important to note that “warming up” a car in a garage, even if the garage door is open, can produce hazardous levels of CO and fumes may build up inside a home. In addition, CO can be found in car tailpipes blocked by snow.

Blizzard Iowa 1973

April 1973 Iowa blizzard (Image credit: National Weather Service (NWS) Des Moines)

Increased exposure time to existing indoor air pollutants like mold

The more time spent indoors during the extreme cold offers more opportunities for pollutant exposure. Common indoor air pollutants like mold, pollen, dust, and volatile organic compounds (VOCs, which are gaseous pollutants) may continue to cause harm. This problem is made worse because windows and doors are closed and every effort is made to keep the cold air from entering. This means that allergens can build up inside.

Mold is an indoor air pollutant that grows in moist conditions, which seems unlikely with the dry heat circulating inside homes during the wintertime. However, there are winter moisture problems to consider. Though forced air heating systems make the air drier, certain areas of the home can become moisture-intense because of a lack of ventilation. Measures like weatherstripping and caulking that are designed to keep cold air outside mean that less of it can infiltrate a home to reduce humidity levels. Additionally, water problems can occur during the winter, like melting snow from the roof that leaks into an attic.

Greater levels of wood smoke, viruses

wood smoke coming out of a chimney on a home

Image credit: Northwest Clean Air Agency (

People may use wood stoves or fireplaces as secondary sources of heat during extreme cold. Wood smoke contains fine, respirable particles as well as toxic gases, both of which may cause harmful health effects. Wood smoke becomes a big problem during the winter because the cold air prevents it from rising and dispersing in the outdoor air. In neighborhoods where wood is burned, smoke can enter the inside of any home in the neighborhood through cracks, even if windows and doors are closed.

Another type of pollutant that increases during the winter is viruses. Research suggests why flu viruses are more infectious during this time–their outer membranes become fortified in colder temperatures, protecting them so they can spread from person to person. Overall, as people spend more time together in confined spaces, there is a greater chance of spreading viruses.

7 steps to safer indoor air during the winter

Here are some steps to ensure safe air quality during the winter, especially when extreme cold weather strikes:

  1. Ensure carbon monoxide detectors are working properly.

    carbon monoxide detector
  2. Carbon monoxide detectors should be installed on every level of a home, located near bedrooms so that family members can awaken if the alarm sounds. The batteries should be changed according to directions–typically once or twice a year, and the CO alarm itself should be replaced every 5-7 years according to directions.
  3. Observe safe practices with generators, space heaters, fireplaces, and other fuel-burning appliances. It is best to have a licensed contractor check your fuel-burning appliances and maintain and properly vent them to the outside. Vent pipes, flues, and chimneys should be inspected for blockages or leaks. Always use portable generators outdoors in areas of good ventilation and away from windows, doors and vents.
  4. Never leave a car running in the garage. It is important to never “warm up” a car in the garage. Even if the door is open, this presents a big CO danger and can cause a buildup of fumes inside the house.
  5. Inspect for mold growth on windows or other areas of condensation, as well as ceilings. It is best to check for and remove mold from problem areas caused by winter moisture.
  6. Reduce levels of volatile organic compounds (VOCs) where possible. VOCs can be released into the air when using personal care products or cleaning products, as well as air fresheners. They are also released from products that are being stored. It is best to reduce their use as much as possible, as the lack of ventilation because of closed doors and windows can cause them to concentrate indoors.
  7. Clean inside to reduce dust and other allergens that have settled and can be released into the air. Dust and other allergens will settle into different places within the home but release back into the air when disturbed. To prevent an increase of these allergens and greater exposure because of sealed indoor conditions and more time spent indoors, it is best to reduce their levels with a thorough cleaning. It is also a good idea to replace or clean central heater filters, which can trap dust.
  8. Wash hands often. Washing hands often is important because colds and flu can be spread through contaminated surfaces, including hands. The CDC recommends washing for at least 20 seconds with warm water and soap.

Using air purifiers during the winter

There are three strategies the EPA lists for reducing indoor air pollutants: source control, ventilation, and air cleaners. The first one, source control, is removing or reducing the individual sources of indoor air pollution, some examples of which are discussed above. The second one, increasing ventilation, is usually not possible during cold weather conditions. Therefore, along with source control, using an air purifier may be an effective strategy to reduce indoor air pollution that is often exacerbated by extreme cold. Please note that an air purifier cannot address CO levels and it is important to follow the steps above to prevent dangerous levels of CO from accumulating inside.

If you are considering purchasing an air purifier to control indoor air pollution, especially during the extreme cold months of winter, you can learn more about the technology inside the Molekule air purifier here. Molekule’s technology can destroy VOCs that concentrate indoors during the winter, as well as viruses. It also eliminates other pollutants like mold, dust, pet dander and other allergens, which can also build up inside during the extreme cold.

Extreme cold weather persists

map of extreme cold weather in the eastern and southern us

Image credit: National Weather Service (

The National Weather Service has issued a winter advisory for this week, warning that “a powerful nor’easter is expected to bring snow, ice, rain, very strong winds, and rough surf to coastal locations of the Southeast U.S., Middle Atlantic, Northeast, and into New England.” As long as these conditions persist, it is important to stay safe from outdoor conditions. While inside, staying safe from indoor air pollution by following the steps discussed above should also be considered.

Headline image: A Chilly End to 2017 for the Northeast, December 29, 2017 (Image Credit: NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response)


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