Floating COVID-19 particles with a blue background.
Illustration: PGN

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What you need to know

  • The CDC set a first-ever target for how much ventilation a building should have to prevent virus spread. The agency recommends at least 5 air changes per hour (ACH) of clean air. 
  • Improving ventilation indoors can help reduce the spread of COVID-19 and other viruses, which is crucial as we enter a new stage of the pandemic. 
  • There are many easy ways to improve air circulation and cleanliness indoors. 

On May 12, the CDC updated its Ventilation in Buildings guidance to include its first-ever target for how much indoor spaces should be ventilated to prevent the spread of viruses. As we enter a new phase of the pandemic, the move highlights the importance of indoor air quality and ventilation to prevent the spread of COVID-19 and many other viruses like the flu. While there were ventilation recommendations before, they didn’t establish a specific ventilation target. “It’s a monumental shift,” said Joseph G. Allen, a Harvard University professor and director of the Harvard Healthy Buildings Program, to CNN. “We haven’t had health-based ventilation standards.”

Read on to find out more about what this means and how you can improve the air quality in your own spaces. 

What, exactly, did the CDC update in its guidance on ventilation in buildings?

The CDC updated its Ventilation in Buildings guidance to include a target for how much ventilation rooms and buildings should have. The agency now recommends at least 5 air changes per hour (ACH) of clean air to reduce the number of germs in a space. The agency added that “this can be achieved through any combination of central ventilation system, natural ventilation, or additional devices that provide equivalent ACH to your existing ventilation.” In a Washington Post op-ed, Allen explained that the goal is to replace the air in a room five or more times an hour. To put it in context, he said a typical home has less than 0.5 ACH. It’s the first time in history that the agency set a specific ventilation target to prevent the spread of respiratory illnesses. 

What does this mean in the new stage of the pandemic? 

The updated guidance is especially important as we enter a new stage of the pandemic following the end of the country’s COVID-19 public health emergency. Air quality experts say that having a target for air ventilation is a landmark move that will help prevent the spread of COVID-19, other respiratory illnesses like the flu and RSV, and hazards like wildfire smoke. Ventilation mitigation strategies can help reduce the concentration of viral particles in the air. The lower the concentration, the less likely the viral particles can be inhaled into the lungs; reach the eyes, mouth, and nose; or accumulate on surfaces. The new recommendations underscore the importance of air quality in preventing the spread of COVID-19. 

What are some ways I can improve ventilation in indoor spaces?

Some of the methods the CDC outlines in its guidance to improve air circulation include opening windows (when the weather allows) and using a window fan to “exhaust room air to the outdoors.” Additionally, to improve air cleanliness, the agency suggests upgrading your central HVAC filter efficiency to a Minimum Efficiency Reporting Value (MERV)-13 or better and using high-efficiency particulate air (HEPA) filters (also called air purifiers). Find the full list of ventilation mitigation strategies, including cost considerations for each, here.