Engineering Strategies for Airborne Diseases

H V A C S Y S T E M S T R A T E G I E S

O2

AIR FILTRATION – CENTRAL

Air Filtration systems are utilized to remove air borne contaminants from HVAC systems. Contaminants can be in form of particles and chemical gases and vapors. Conventional filtration systems capture particles by passing airflow through the media. The fraction of particles removed from the air is termed “filter efficiency” and is provided by the Minimum Efficiency Reporting Value (MERV) under standard conditions. These systems are not very effective in removing gas and vapor molecules. • MERV 13 or greater are efficient at capturing airborne viruses. • MERV 14 filters are preferred. • HEPA filter efficiencies are higher than MERV 16 but will have higher pressure drops . Carbon filters are effective with chemical gasses but cannot be utilized for capturing airborne viruses. Utilization of carbon filters on outside air can be beneficial in areas with poor outside air quality. Filtration systems utilize different mechanisms for capturing particles. “Straining” captures particles larger than the openings on the media, but it is not the only method. Inertial impingement, interception, diffusion and electronic effects allow capturing particles that are smaller than the filter openings.

Silt

Gravel

Sand

Volcanic & Industrial Ash