EPA’s stand is that mere improvements in ventilation and filtration cannot eliminate the risk of SARS-CoV-2 transmission on their own. It suggests increasing ventilation and air filtration along with implementation of other precautions like social distancing, wearing cloth face coverings or masks, surface cleaning and disinfecting, and hand-washing.

ASHRAE’s take is that ventilation and filtration provided by HVAC systems can reduce airborne concentration of COVID virus and thus the risk of transmission through the air. ASHRAE recommends that building operators use a filter with a Minimum Efficiency Reporting Value (MERV) of 13, but suggests that a MERV 14 filter is preferred.

MERV system for filters

MERV system on the measurement scale (1-16), created by ASHRAE, is designed to report the effectiveness of air filters. Smaller particles are captured through filters with a higher MERV rating. A usual business, including a restaurant, might have a MERV-8 filtration system, which captures larger particles.

“Those filters don’t do anything really for COVID,” said Patrick O’Neill, North American President at mCloud Technologies, that works with retailers and restaurants to ensure their indoor air quality meets or exceeds commercial building standards established by ASHRAE.

WHO’s guidance on ventilation and AC systems

For safety, World Health Organization (WHO) along with World Meteorological Organization Joint Office for Climate and Health and U.S. National Oceanic and Atmospheric Administration – has recommended several steps to improve indoor ventilation and air filtration to improve air quality:

  • Consider using natural ventilation, opening windows if possible and safe to do so.
  • For mechanical systems, increase the percentage of outdoor air, using economizer modes of HVAC operations and potentially as high as 100%.
  • Consider running the HVAC system at maximum outside airflow for 2 hours before and after spaces are occupied.
  • Increase total airflow supply to occupied spaces, if possible.
  • Disable demand-control ventilation controls that reduce air supply based on temperature or occupancy.
  • Improve central air filtration.

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