Understanding Your Ventilation System

By: Allen M. Chung, CIH and Paul Linnartz

As people start to return to office buildings and public areas after more than a year of “pandemic life,” there will undoubtedly be a heightened awareness of air quality in closed spaces.

Certain viruses, such as SARS-CoV-2, are known to spread through aerosolized respiratory droplets at close range. Airborne transmission from exposure to tiny droplets is unlikely over long distances but possible in certain indoor spaces. General ventilation typically addresses common contaminants often found in commercial environments, but many commercial systems have not been designed to protect occupants from contagions like the SARS virus. Therefore, understanding a facility’s general ventilation system is an essential step toward improving indoor air quality (IAQ) as well as moderating the risk of spreading disease at your facility.

To help you moderate the spread of contagious diseases in an indoor space, the National Center for Biotechnology Information (NCBI) published an article that recommends the following:

  • increasing air exchange rates above current conditions
  • using high‐efficiency filtration for recirculated air (MERV 13 or higher)
  • verifying that sensitive areas, such as bathrooms and rooms where infected patients are cared for in hospitals and senior homes, are negatively pressurized relative to adjacent areas
  • managing airflow direction and speed to prevent the spread of aerosols across occupants
  • considering additional technological controls, such as UV germicidal irradiation and portable air purification, in areas and situations where typical building‐level controls are not sufficient

Ventilation effectiveness is measured in terms of Air Changes per Hour (ACH). By running the recirculated air through high-efficiency filtration (MERV 13 or higher), possibly adding UV germicidal irradiation and portable air purification units, more “clean” air is provided to the indoor space. The amount of clean air needed can vary widely depending upon building design and occupancy. ASHRAE, which sets ventilation standards and guidelines, recommends ACH levels up to 3x/hr for offices, 6x/hr for schools, and 8x/hr for restaurants.

Do you know what your ACH rate is?

Evaluating air exchange rates (ACH), checking negative pressure at sensitive areas, and mapping airflow direction and speed in your facility can determine whether your ventilation systems promote healthy indoor environmental conditions. This can be a complicated process.  If Emilcott can be of any assistance, reach out to

Summertime IAQ Checklist

June is National Safety Month! For 25 years, the National Safety Council (NSC) has been celebrating National Safety Month as an annual reminder to “keep each other safe from the workplace to anyplace.”

The topic for this week is: Address Ongoing COVID-19 Safety Concerns.

Public spaces are preparing their returns to normal operation as we finally turn the corner on this pandemic. After a year of reduced capacities and heightened awareness of air quality in closed spaces, property managers need to make sure their air handling maintenance is ready.

Using our 30 years of experience with indoor air quality, Emilcott has compiled a checklist to help you verify that your building’s air quality is in peak shape for summer openings.