What Are The World Health Organization Guidelines for Indoor Air Quality?

June 12, 2020

The World Health Organization, or WHO, is a group of health scientists, doctors, and public health specialists who create guidelines around all types of issues that affect human health, including indoor air quality. The indoor air in most homes is two to five times more polluted than the outside air, and the air in Hudson, FL, houses is no exception. At Mario's AC, our technicians will follow WHO guidelines when evaluating your property’s indoor air quality and making recommendations for solutions. Here is what you need to know about WHO’s indoor air quality guidelines and some tips on what you can do in order to improve the quality of your home’s air.

Household Fuel Combustion

The WHO has created guidelines around the combustion of household fuels. While most Americans do not burn coal to heat their houses, natural gas furnaces, propane heaters, and wood fireplaces count as household fuels. The WHO guidelines around burning fuels for heat or cooking in your home include a recommendation of no particles less than 2.5 microns in size. The guidelines also recommend that carbon monoxide levels should not exceed 0.16 grams per minute of flow rate in a vented room. The amount of nitrous oxide should also not exceed 0.16 grams per minute. In their guidelines, the WHO recommends that all kitchens have active and passive vents to remove carbon monoxide that is used for cooking and heating.

Outdoor Fuel Combustion

The WHO guidelines recommend that you follow the same rules when burning fuel outside as you do inside. For example, if you are using a gas grill, you will be exposed to a lot of byproducts from the combustion of the propane gas. Even though the exposure duration is relatively short, standing next to the grill puts you at a relatively high exposure level. The same is true for using a gas-powered lawnmower, leaf blower, or another outdoor item. If you burn yard waste or light a bonfire in your yard, follow the WHO’s guidelines for indoor exposure to fuel combustion in order to stay safe and protect your health.

Chemical Indoor Air Pollutants

There are many types of indoor air pollutants tracked and evaluated by the WHO. The WHO is concerned about many chemicals that off-gas from products that are a part of your house or that you bring into your home, particularly formaldehyde. It is the most common chemical involved in off-gassing. The WHO guidelines recommend that the level of formaldehyde in your residence be no higher than 2.0 parts per billion. In a typical home that is made with standard construction techniques, the level is 20 parts per billion. In a manufactured house, the average level of formaldehyde is 40 parts per billion. Exposure to formaldehyde causes many short-term health problems, including eye, nose, and throat irritation, dizziness, nausea, fatigue, and confusion. If you are constantly exposed to a high level of formaldehyde in your home, you may also suffer from long-term health effects. These include an increased risk of heart disease, lung cancer, kidney disease, and other types of cancer.

Biological Indoor Air Pollutants

The WHO tracks biological forms of indoor air pollution, which include mold and bacteria. These microorganisms release spores. When you breathe in the spores, they settle into the tiny air sacs in your lungs. Once the spores are in your lungs, your body starts an inflammatory response. The inflammation leads to chronic breathing problems. In the short-term, exposure to mold spores can lead to headaches, dizziness, fatigue, malaise, and nausea. Exposure to bacterial spores can lead to lung infections such as pneumonia. The WHO recommends that indoor mold spore levels be no higher than 1,500 counts per cubic meter of air. However, some molds are toxic to your body even at very low levels. For example, 50 to 200 spores per liter of air of Stachybotrys or Memnoniella can have serious health consequences.

Secondhand Smoke

The WHO offers guidelines on exposure to secondhand tobacco smoke. No level of exposure to secondhand smoke is safe. The WHO recommends that smoking not be allowed in homes, including multi-unit apartment buildings. Secondhand smoke can transfer from one room to another or one unit to another through the HVAC system. Levels of secondhand smoke higher than 10 micrograms per cubic meter can impact a child’s breathing. The same level also increases everyone’s risk of lung cancer and other chronic breathing disorders.


Radon is another indoor air quality problem with these guidelines. The WHO states that no level of radon is safe. However, the organization also recognizes that there is no way to eliminate all radon from a structure. Radon is a byproduct of the natural decomposition of uranium in the soil. Some places have higher radon levels than others. For example, glaciers deposited clay soil throughout the Ohio Valley, so many houses throughout Ohio have naturally high radon levels. Radon is the second-highest leading cause of lung cancer after smoking, and it is the top cause of lung cancer in people who do not smoke. Radon is a gas, and it is heavier than air. It seeps into a home through gaps and cracks in the foundation or footing. The average amount of radon outdoors is 0.4 picocuries per liter. The WHO and the United States Environmental Protection Agency recommend installing a radon mitigation system if the level of radon in your residence is higher than 2.0 picocuries per liter.

Controlling the Sources of Indoor Air Pollution

The WHO and the Environmental Protection Agency recommend controlling the sources of indoor air pollution. When you buy a new piece of furniture or plastic item, let it off-gas outdoors. Choose paints, adhesives, and cleaners that are low in volatile organic compounds. Select items that are free of formaldehyde and other chemical treatments, too.

Recommended Products for Improving Indoor Air Quality

The WHO does not recommend any specific products for improving indoor air quality. However, you can review each manufacturer’s literature about how many mold or bacterial spores or particles an air purifier or air filter can remove from your house’s air. There are many makes and models of whole-home air purifiers available. They use different types of technology. The WHO has evaluated some of these technologies, including UV-C, ozone, and electrostatic filters. The WHO has found that UV-C air filters are able to inactivate most bacteria and other biological pollutants in residences. The United States Environmental Protection Agency recommends using an air filter with a minimum efficiency reported value (MERV) rating of at least 13. These filters remove particles as small as 3.0 microns in size. For even better filtration, invest in a filter with a MERV rating of at least 16. This is a medical-grade filter that captures viruses, bacteria, mold spores, oil droplets, aerosols, chemical vapors, and other air pollutants.

At Mario's AC, we are proud to be your local indoor air quality experts in Hudson. Our NATE-certified technicians also offer reliable heating and air conditioning maintenance, repairs, replacement, and installation services. Additionally, you can count on us for duct cleaning, which removes the dust and dirt from your home’s air ducts. We also provide commercial heating and cooling services. To learn more about the WHO guidelines for indoor air quality or any of our residential or commercial services, call us today.

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