Using your HVAC System Against COVID-19

by Scott Henriques

Since the COVID-19 virus is primarily transmitted via the aerosol of human expiration, your school’s HVAC system can play a critical role in the virus’ transmission. As an HVAC engineer, people often ask me if they can do anything with their existing HVAC systems to help mitigate the spread of the virus. While each individual HVAC system will have limitations as to what can be achieved, here are some practical approaches that might be applicable for you.

1. 1. 

      Duct-mounted bipolar ionization generator

      Ensure your HVAC equipment is routinely serviced. Worn belts and clogged filters can reduce air flow, and malfunctioning or stuck dampers can inhibit proper amounts of outside and exhaust air.
   2. Increase the effectiveness of the HVAC filtration system. Air filters in the majority of existing buildings are not designed to capture microscopic biological matter. Filters such as MERV-13 filters, however, are designed to arrest particles the size of a water droplet, the primary carrier of COVID-19 and a host of other biological contaminants. These more restrictive filters, though, will increase the back pressure of the fan system and reduce the amount of air flow, but in some cases the fan speed can be increased to compensate for this.
   3. Increasing the amount of outside and exhaust air will reduce the concentration of particulates, decreasing the probability of an infection. This strategy is most effective when outside temperatures are moderate and the heating and cooling coils are not stressed. This may increase your energy costs though and will be limited by the actual equipment.
   4. If you’re interested in actually disinfecting the air in your buildings, two primary means are germicidal ultra-violet light (UV-C) and bipolar ionization (BI). A typical UV-C system involves exposing the air to biologically destructive UV light, killing the virus over time, similar to the way a pool skimmer collects surface contaminants. BI involves installing a BI generator in the HVAC equipment to flood the space to a specified concentration to destroy the virus and other contaminants, similar to shocking a pool with chlorine.

No matter your situation, my best advice is to hire a reputable HVAC engineer, the equipment manufacturer’s representative, or an HVAC contractor to help you determine your best option or combination of options.

Scott Henriques, PE, LEED AP, CEM is a senior project manager at Weston & Sampson.