An Air Filtration Primer for Building Owners and Developers

The coronavirus pandemic has left all of us eager for a return to some form of normalcy. At Gensler we’re looking at ways to make key changes to the built environment so we can help our clients create safer spaces for people as they return to work.

To that end, we recently hosted a panel discussion with three leading mechanical engineering firms to discuss indoor air quality. Gary Pomerantz, Mechanical, Engineering, and Plumbing leader from WSP; Robert Ioanna and Robert Bolin, MEP and architectural engineering leaders at Syska; and Kurt Karnatz and Saagar Patel, respectively the president and Energy+Eco studio leader at ESD Global, all participated in this discussion and contributed to this blog post.

According to our panel, in order to consider indoor air quality as a way to mitigate the spread of viruses, we first have to determine how air quality impacts viruses and other air-driven pathogens.

Per the CDC, there are three basic means of disease transmission for non-bloodborne pathogens: direct physical contact, droplets from coughing and sneezing, and inhalation of airborne particles. While rigorous cleaning and social distancing can help address direct contact and transmission from droplets, airborne transmission may be directly impacted by the specific air distribution system of the building you inhabit.

As noted in ASHRAE’s recent position document on infectious aerosols, there are three ways to potentially mitigate airborne pathogens with a mechanical system: trap it (filtration), kill it (disinfection), or flush it (ventilation). From a design perspective, these different approaches typically overlap, and the right strategy depends on the HVAC system you are starting with.

To trap airborne particles, review your current air filtration system, replace the existing filters and look at upgrading to a higher rated filter. In some cases, this can be done with little impact to the existing system. In others, modifications might be necessary depending on the air pressure available in the system. Filter types and selection should be reviewed with a mechanical engineer for the desired outcomes.

For “hot-spots” such as conference centers, restrooms, and lobbies consider adding stand-alone filtration units such as portable HEPA filters that are visible and will help make your mitigation efforts more apparent. And be sure to prepare a filter replacement program that considers the potential contamination of the replaced filters.

Another approach beyond filtration is to disinfect the air that is being conditioned. One of the most common disinfectant systems for HVAC uses UVC light to kill viruses in ductwork. Some mechanical systems may already have this feature, so simply replacing the UVC lamps can increase the potency of the system.

Beyond UV disinfectants, developers could consider bipolar ionization and photocatalytic oxidation. These systems charge the existing air to kill pathogens, and they don’t require more outside air. Reliable testing for these systems is still in early stages, but the advanced technology shows potential.

Increasing the amount of fresh or outdoor air and increasing the air change rate is the most common and proven approach to reducing unwanted airborne particles. Shifting your system into full air economizer mode, increasing your outdoor air damper positions, and adding air changes by night-flushing the system or running it continuously can all be effective approaches. Such frequent air exchanges will impact energy use and operating costs, but they are a necessary first step in helpi