How to create airflow in a room

With the next wave of COVID-19 around the corner and coinciding with the flu season, it’s apparent that the transmission of the airborne disease is a bigger problem during the fall, winter, and spring seasons. One big factor which causes this is the fact that people spend more time inside during these seasons than in the summer.

How we create airflow in a room is dependent on the building’s HVAC design and what we primarily design our systems to do is ensure we have adequate ventilation coverage. The idea is if we can ensure proper coverage the HVAC system has a better chance of diluting viruses and bacteria within a safe period. A building’s HVAC system can be degraded significantly if the airflow patterns are not calculated properly. If our systems are experiencing short-circuiting, then our effective airflow patterns are often below 10% of what the design shows. What this does is provides significantly less dilution and protection against airborne diseases than we originally thought.

There are three basic diffuser configurations in most buildings in use which are Ceiling Supply/Ceiling Return; Floor Supply/Ceiling Return and Ceiling Supply/Floor Return.

Ceiling Supply/Ceiling Return is the most common diffuser configuration and has the greatest potential for short-circuiting. This configuration also provides the greatest potential for virus transmissions as the airflow pattern is from high to low and back to high again.

Floor Supply/Ceiling Return is used in a lot of heating systems and takes advantage of the warm air’s reduced density to aid in the raising of airflow from low to high. This configuration is very effective in reducing airborne disease transmission as the airflow patterns as the airflow is always traveling from low to high with minimal cross-flow between occupants.

Ceiling Supply/Floor Return is the most effective way to create airflow in space as in this configuration any viruses transmitted have a lower probability of infection among occupants and if any viruses are present they will either be removed by the low-level diffusers or will attach to the floor where they can be easily disinfected by the cleaning process.

Atlabach Consulting is a world leader in providing Computational Fluid Dynamic Modelling of virus transmissions within a building along with Probability of Infection Analysis to fully understand the health and safety of your occupants currently and afterward. www.atlabach.com