— By Danny Miller, Transformative Wave —
The airborne transmission of COVID-19 has impacted many retail and restaurant facilities in their ability to safely operate indoors. As facility operators look to comply with COVID-19 safety guidance, there are three battlefronts that have arisen: disinfection, filtration and ventilation. Numerous products are being marketed and confusion can arise about what should be the priority.
Disinfection attempts to kill the virus include using products like UV-C lights or bipolar ionization. UV-C has been shown to be effective but largely on stationary surfaces. Both technologies require a sufficient amount of exposure to effectively kill the virus. These technologies can be deployed as central installations in the HVAC system or as local devices dispersed around a facility. Standalone portable appliances have limits because they may only be treating a very small portion of the room air.
Central deployments in the HVAC units or ducts are in a better position to expose a greater volume of room air to the UV light, but there are still going to be questions about exposure. It may take multiple passes of the virus before lethality is achieved. The flow rate of air through an HVAC system varies by design and level of maintenance. Slower airflow will allow more exposure time and faster flow will decrease exposure. Because of this, it is uncertain at what level these technologies are effective in killing the virus. Both technologies have safety concerns to consider.
Installing air filters rated for capturing particles down to the size of the COVID-19 virus does not guarantee removal of the virus. One of the reasons is related to how circulated air can bypass any filtration via paths around the filter in most HVAC systems.
As filters get dirty, resistance increases and the propensity for air to bypass them becomes greater. Air takes the path of least resistance. Special care must be taken to seal off any of these alternative paths so that “all” of the air is forced through the filters. Most HVAC systems serving restaurants or retail are limited in their ability to accommodate filters capable of trapping viruses. Improved filtration is an important step but not a cure-all.
Ventilation is being emphasized by the CDC as key to diluting and removing the virus from indoor environments. Specific steps are recommended and critical to retail and restaurant facilities looking to reopen and keep customers safe. Increased ventilation brings more fresh air indoors to flush out and dilute possible contaminants. Facility operators can do this by manually reconfiguring each HVAC unit’s outside air dampers to a higher level and extending the operation of the HVAC fan. This can be a time-consuming and costly process if multiple locations are involved. Alternatively, facility managers can retrofit the HVAC unit with a suitable technology to enable remote automated adjustments of the schedules and damper positions.
Retail and restaurant facility operators must take seriously the airborne transmission of COVID-19 and carefully evaluate disinfection, filtration and ventilation options for ensuring safe indoor operation. All three measures should be considered as they are not a substitute for one another.
— Danny Miller is president of Transformative Wave, a leading innovator in HVAC energy efficiency and building automation solutions, specializing in HVAC ventilation strategies.