The CDC’s Recommended Ways to Reduce COVID-19 Transmission

A whole range of technologies and solutions for COVID reduction in schools, offices, and homes have burst onto the market. But which ones work at reducing COVID-19 spread, and which ones don’t? The CDC has published a detailed article outlining their recommended ways to improve ventilation and reduce COVID exposure. In this article, we run through the most important points.

CDC: Ways to Reduce COVID-19 Spread Indoors

1) Improve Ventilation

The CDC’s top recommendation to reduce COVID-19 spread is to improve indoor ventilation. They suggest improving ventilation by:

  • Adjusting HVAC systems to increase airflow to occupied spaces when possible.
  • Opening windows and doors to increase outdoor air flow (even a slightly open window can help ventilation).
  • Using indoor fans to increase the effectiveness of open windows.
CDC recommends opening windows to reduce COVID-19 spread
Simply opening a window can significantly reduce viral concentrations indoors

The great thing about these strategies is they are often free or low-cost and are very effective. A CDC study of schools in Georgia showed that simple strategies to improve ventilation lowered COVID-19 spread by 30%.

CDC studys shows improved ventilation reduced COVID-19 spread by 30%

2) Use Filtration Methods Such as Portable HEPA Air Purifiers

The CDC also recommends mechanical filtration as a method of removing COVID from the air. This method works by using filters that are able to capture virus-sized particles and remove them from the air.

The CDC provides two ways to filter the air in a building:

  • Using central air filtration. Filters rated MERV-13 and above are efficient at capturing airborne viruses. They can typically be installed in existing central air systems, as long as it does not over-work the system’s fans.
MERV-13 filters for HVAC system to filter out COVID-19
MERV-13 being installed in an HVAC system

Portable HEPA filtration units that combine a HEPA filter with a powered fan system are a preferred option for auxiliary air cleaning, especially in higher risk settings such as health clinics, vaccination and medical testing locations, workout rooms, or public waiting areas.

Center for Disease Control and Prevention (CDC) on HEPA filters for COVID-19 mitigation
Smart Air Sqair air purifier used for clean air filtration in school classroom

In the same Georgia school study mentioned above, the CDC found that HEPA filter air purifiers in the classroom lowered infection rates by 41%. That’s even better than the 29% by ventilation alone.

When choosing a HEPA air purifier, the CDC states it’s important to select a purifier that is appropriately sized for the area it will be installed in.

Read More: How to Calculate if a Purifier Is Strong Enough for an Area

3) UV Light – Only When Other Options Are Limited

The CDC recommends using UV light only as a last, supplemental solution “when options for increasing room ventilation and filtration are limited.” There are two types of UV Light solutions available:

  1. Ultraviolet Germicidal Irradiation (UVGI) – either in air ducts or in upper rooms
  2. Far-UV (or Far-UVC) – an emerging technology that is currently heavily marketed.

The CDC does not recommend UV light as a primary solution to COVID protection because:

  1. UVGI is more costly to install and maintain, and may cause temporary eye or skin damage as well as damage to plants.
  2. Questions remain about Far-UV’s overall safety and its mechanisms for killing organisms. As an emerging technology, there is also little peer-reviewed data to show how well it works, unlike for example HEPA filters.
UVGI UV light for COVID-19 protection
UVGI for HVAC systems

4) Ozone

ASHRAE notes that because ozone is dangerous to humans – and plants and all living animals – it should only be used to disinfect unoccupied spaces.

Many companies claim to limit their ozone levels to within the ‘safe’ limits. However, the EPA points out that at these lower levels, ozone “does not effectively remove viruses, bacteria, mold, or other biological pollutants”.

CDC does not recommend ozone for COVID-19 protection indoors
Ozone generator on Amazon

5) Bi-polar Ionization & Other Emerging Technologies

The CDC takes a cautious stance regarding “emerging technologies” that include the use of ionization, dry hydrogen peroxide, and chemical fogging disinfection. The CDC notes “relative to other air cleaning or disinfection methods, they have a less-documented track record when it comes to cleaning/disinfecting large and fast volumes of moving air within heating, ventilation, and air conditioning (HVAC) systems or even inside individual rooms.”

Convincing scientifically-rigorous, peer-reviewed studies do not currently exist on these emerging technologies; manufacturer data should be carefully considered.

ASHRAE on bipolar ionization and other emerging technologies
CDC is cautious regarding emerging technologies such as bipolar ionizations for COVID-19 protection indoors
Plasma Air 600 Bipolar Ionizer

The CDC encourages consumers to exercise caution with these emerging technologies and the claims they make. They also mention that when considering technologies that can expose building occupants, the “safety data should be applicable to all occupants, including those with health conditions that could be aggravated by the air treatment.”

For further information on the CDC’s recommendations for COVID mitigation indoors, check out the CDC’s website.

Bottom Line: CDC Recommended Ways of Reducing COVID Spread Indoors

The two primary recommendations the CDC makes on making indoor spaces more COVID safe include: dilution (improving ventilation) and mechanical filtration (MERV-13+ filters in HVAC and portable HEPA purifiers).

UV lights can be used if these two options are unavailable, otherwise UV lights serve little benefit. The use of ozone is not recommended as any effective dose will exceed health guidelines and be dangerous to humans. Finally, the CDC takes a cautious stance on “emerging technologies” such as ionization due to its lack of track record in cleaning/disinfecting large volumes of air and lack of scientifically-rigorous studies.

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