Breathing clean air is crucial for good health.1 But we all spend most of our time inside buildings where the air supply gradually grows stale.2 In other words, there’s less oxygen and more carbon dioxide (CO2) within our spaces. CO2 is a direct proxy for the overall wellness of the air supply.3 As levels rise, the likelihood of pollutant and pathogen concentration increase in tandem.

The most common solution is refreshing the air with some form of ventilation; usually opening windows. Unfortunately, it isn’t always possible to allow outside air to circulate in. This can be due to outdoor pollution, significant temperature differences, not having a window, etc. But even so, maintaining proper IAQ is essential. 

In this article, we’ll detail 11 practical tips for boosting IAQ without having to open the windows.  

  1. Open the doors: By leaving internal doors open, air can circulate freely between rooms, allowing fresh air to flow in and stale air to move out. In addition, cracking doors can help to distribute conditioned air more evenly throughout building spaces, helping ensure that occupants are comfortable.
  2. Use alternate forms of ventilation: Exhaust fans and similar machinery are ideal for removing excess moisture and pollutants in high-risk areas like bathrooms and kitchens. When cooking, try using vented range hoods that lead outside. These are particularly effective for removing the fumes and contaminants generated by heating food. From there, devices like air purifiers can help clean indoor environments. These work by running air through various filters: high-efficiency particulate air (HEPA), activated carbon, UV-C light, etc. Using air purifier reduces the concentrations of allergens, dust, smoke, and other pollutants. Please be aware that filters require regular cleaning and replacement to continue functioning optimally. 
  3. Maintain HVAC systems: Heating ventilation and air conditioning (HVAC) systems can become breeding grounds for mold and bacteria if they aren’t well maintained. This can become a big problem, as the pollutants could be dispersed through every vent the system feeds into. As such, it’s worth regularly checking, cleaning, and maintaining HVAC pathways to ensure functional performance. 
  4. Choose low VOC paint: Many commercial paints emit volatile organic compounds (VOCs) that can compromise air quality.4 To prevent these releases, choose low-VOC or zero-VOC paint to minimize indoor air pollution. When remodeling a space, consider using natural paints made from plant-based ingredients for healthier indoor environments. 
  5. Do regular cleaning: Dust, pollen, and other contaminants gradually accumulate indoors. However, regular cleaning effectively removes these pollutants. Vacuuming carpets, rugs, and upholstered furniture makes a big difference – particularly when paired with specialized high-efficiency particulate air (HEPA) filters. It’s important to remember to clean and/or replace aged vacuum components and filters. And if vacuuming isn’t an option, consider mopping floors and wiping surfaces with wet materials to gather impurities rather than simple sweeping and wiping.
  6. Use doormats: A massive amount of outdoor pollutants enter buildings on the bottoms of our shoes.5 Using doormats at entry points can help trap dirt and dust before it enters a home, apartment, etc. For additional protection, consider using a series of doormats (outside and inside) to maximize their effectiveness. Then, make sure to clean doormats regularly to prevent material buildups that can be tracked inside. 
  7. Use natural cleaning products: Many commercial cleaning products contain harmful chemicals that can compromise air quality.6 On the other hand, natural cleaning products such as vinegar, baking soda, and lemon juice can clean effectively without emitting harmful vapors. It’s not difficult to make your own cleaning products using natural ingredients or buy naturalistic cleaning products from stores.
  8. Control internal humidity: Fluctuations in humidity can cause mold and mildew growth, which worsens IAQ and contributes toward health problems.7 If you’re aware of spikes in humidity, devices like dehumidifiers can help maintain optimal IAQ. Keep overall humidity levels below 50% to prevent mold growth. It’s worth keeping a ready eye on high-risk areas such as the bathroom and kitchen.
  9. Avoid smoking indoors: Tobacco smoke is a major indoor air pollutant that can contribute to a range of health problems. If you smoke, it’s best to do it outside so the vapors aren’t trapped inside with inhabitants. 
  10. Keep pets clean and groomed: Pet dander, hair, and odors reduce air quality. To keep things healthy, regularly groom and bathe pets. This minimizes shedding and dander release. In addition to normal cleaning efforts like vacuuming, air purifiers can help remove pet dander from the air.
  11. Add some houseplants: Houseplants are considered by many to be a natural method of improving indoor air quality. This theory stems from a study by NASA on the ability of plants to scrub out harmful materials and CO2 from the air while releasing oxygen.8 However, it is important to note that the effectiveness of houseplants in improving indoor air quality is still somewhat controversial due to the restrictions placed on that study. With this in mind, people seeking air-purifying houseplants tend to gravitate toward spider plants, peace lilies, and snake plants.  

By following these tips, you can create a healthier, more comfortable indoor environment without opening windows. As good indoor air quality is essential for health, it’s worth taking some time to implement these strategies and maybe breathe a bit easer. If you’re interested in tracking CO2, we recommend the Aranet4 HOME Indoor air quality monitor. It’s accurate, durable, portable, easy to understand, and comes with its own app.


  1. Air.
  2. People in the US spend roughly 90 percent of their time indoors. So it’s a little odd that we don’t think more about indoor air quality.
  3. Is CO2 a good proxy for indoor air quality in classrooms? Part 1: The interrelationships between thermal conditions, CO2 levels, ventilation rates and selected indoor pollutants.
  4. VOC Paint vs No-VOC Paint Comparison Guide.
  5. Leave It at The Door: A Guide to Reducing Contaminants in Your Home.
  6. What is indoor air quality and how is it affected by cleaning, sanitizing, and disinfecting?
  7. Moisture Control, Part of Indoor Air Quality Design Tools for Schools.
  8. NASA Plant Research Offers a Breath of Fresh Air. 

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