Face coverings, physical distancing, hand washing, and surface disinfection are well documented actions to minimize potential for occupational transmissions of the virus causing COVID-19 (SARS-CoV-2). But let’s consider how these proven tactics align with the hierarchy of controls from the National Institute for Occupational Safety and Health.
In the case of SARS-CoV-2, the use of Personal Protective Equipment (PPE), i.e. respirators or face coverings, is considered the least effective method of controlling exposures to a hazard. Hand washing, surface disinfection and physical distancing fall in the category of Administrative Controls, one step up from PPE, changing the way people work to reduce exposure to the hazard.
Given that Elimination (physically removing the hazard) and Substitution (replacing the hazard) are not viable options for COVID-19, we suggest implementing the next best control: Engineering Controls, isolating people from the hazard, such as through the use of ventilation and air handling systems.
The Center for Disease Control and Prevention acknowledges that when people with COVID-19 cough, sneeze, sing, talk, or breathe they produce respiratory droplets. Infections occur mainly through exposure to these respiratory droplets, which may occur, the CDC acknowledges, via airborne transmission. One or more of the following factors are typically involved in airborne transmission of SARS-CoV-2:
- Enclosed spaces
- Prolonged exposure to respiratory particles
- Inadequate ventilation or air handling
We suggest employers and building owners take the following ventilation and air handling actions to minimize potential for airborne transmissions of SARS-CoV-2 in workplaces:
1. Equip air handling units with MERV-13 filters or the highest efficiency air filters possible without having detrimental effects on air handling system performance.
Many commercial buildings utilize filters in air handling units that are less efficient than a MERV-13 filter. MERV-13 filters will not remove all virus particles from an airstream, but they can be effective in reducing airborne virus concentrations.
2. Increase the outdoor air supply to the maximum allowed by air handling systems.
Though outdoor air dampers are often set at minimal settings to conserve energy (and energy costs) during winter and summer months, we suggest opening them to their maximum allowed to take advantage of dilution ventilation. Though dilution ventilation will not eliminate airborne contaminants, increasing outdoor air supply rates will dilute airborne viral concentrations in airstreams.
3. Ensure that air handling fans run continuously while buildings are occupied.
With a typical thermostat-controlled system, the air handling fan may only run if room temperatures deviate from the programmed setpoint. Continuous operation of the air handling fans will enable filtration and dilution ventilation to reduce airborne virus concentrations within affected spaces. We recommend turning off demand-control settings for air handling fans that are based on temperature or occupancy.
4. Exercise caution when using personal or pedestal fans for comfort, which can direct exhaled SARS-CoV-2 aerosols from an infected person to nearby people.
If local exhaust ventilation systems (e.g., fume hoods, snorkel exhausts) are being used for other air contaminants, their use should continue. These local exhaust ventilation systems are needed to control occupational exposures to hazardous air contaminants.
If you would like more information about how to optimize your ventilation and air handling systems for COVID-19 protection, please contact us.