Have you had to delay your return-to-office (RTO) date due to surges of COVID-19 in your community? If your employees have already returned, are you worried about the spread of the Omicron variant? Are you skeptical about the value of indoor air quality, or instead, have you wondered about adding portable air cleaners? Have you hoped life at work would just “go back to normal”?
Welcome to the new, new normal.
Ventilation and the science of transmission
COVID-19 is caused by the SARS-CoV-2 virus and is transmitted when someone breathes in small droplets or particles containing SARS-CoV-2, according to the Centers for Disease Control and Prevention (CDC).
The EPA explains that people infected with COVID-19 release particles and droplets of respiratory fluids containing the SARS-CoV-2 virus when they exhale through breathing, coughing, exercising, singing, or speaking. Very fine droplets or particles can continue to spread through the air in the room or space and can accumulate in spaces with poor ventilation.
The CDC recommends avoiding poorly ventilated spaces to help slow the spread of COVID-19, along with hand-washing, mask-wearing, and physical distancing.
One of the first documented outbreaks of COVID-19 in the United States was an indoor superspreading event affecting members of the Skagit Valley Chorale in Skagit Valley, Washington. Following a March 10, 2020, choir rehearsal, 53 members among the 61 attending were confirmed or suspected to have contracted COVID-19 from a single member experiencing cold-like symptoms. Two choir members later died.
The American Conference of Governmental Industrial Hygienists (ACGIH) points out that building ventilation systems are designed for comfort and general air quality and not the removal of particles from an infectious source. The placement of system inlets and outlets can even lead to a concentrated buildup of infectious particles.
The evidence linking poorly ventilated indoor spaces and respiratory infections was established decades before the COVID-19 pandemic. Ventilation problems may even be responsible for higher sick leave costs and lost productivity. In an often-cited December 2000 study, researchers analyzed the sick leave use among employees of a large manufacturer and established a clear risk of increased sick leave use among workers assigned to poorly ventilated spaces. Researchers suggested that the employer could have seen net savings of $400 per employee per year by increasing ventilation. They also concluded that the existing recommendations for outdoor air supply accounted for increased illness and lost productivity.
Earlier this year, a Harvard public health researcher pointed out that current heating, ventilation, and air conditioning (HVAC) standards for air changes per hour for buildings other than hospitals are not designed for infection control. Existing standards are designed for diluting odors and maintaining a basic level of acceptable indoor air quality. The commentary in the Journal of the American Medical Association recommended increasing the number of air changes per hour through increased outdoor air ventilation, recirculated air passed through a filter with at least a minimum efficiency rating value (MERV) of 13, or the use of portable air cleaners with high-efficiency particulate air (HEPA) filters to limit COVID-19 transmission.
The Occupational Safety and Health Administration (OSHA) has advised employers to consult a qualified HVAC professional to ensure optimal building ventilation and that HVAC systems are operating as intended. Ventilation and filtration are part of the agency’s guidance for employers on mitigating and preventing the spread of COVID-19 in the workplace, along with facilitating vaccination, ensuring that workers infected with COVID-19 stay home, implementing physical distancing in communal work areas, providing face coverings or surgical masks as a method of infection source control, training workers in both COVID-19 risks and control methods, and performing routine cleaning and disinfection.
OSHA’s ventilation recommendations are based on the American Society of Heating, Refrigerating, and Air-Conditioning Engineers’ (ASHRAE) guidelines for building operations and industrial settings during the COVID-19 pandemic and the CDC’s Ventilation in Buildings guidelines. The AHSRAE’s recommendations include improving building air filtration to MERV 13 or the highest filter compatible with the system’s filter rack and sealing edges of the filter to limit bypass; keeping systems running for longer hours—24/7 if possible; considering the use of portable air cleaners with HEPA filters; and considering installation of ultraviolet germicidal irradiation (UVGI).
A layered approach
The CDC has described improvements to building ventilation as part of a layered approach to controlling the spread of COVID-19. That layered approach also includes hand hygiene, physical distancing, vaccination, and wearing face masks. The CDC also cautioned that barriers to shield employees, customers, or visitors from infectious respiratory droplets sometimes can hinder good ventilation, unintentionally interrupting the airflow distribution within a space, which can allow a concentration buildup of aerosol particles. However, protective barriers can assist with improved ventilation when used to facilitate directional airflows or desired pressure differentials between clean and less clean spaces.
Methods to improve ventilation include increasing the introduction of outdoor air, using fans to increase the effectiveness of open windows, ensuring ventilation systems operate properly, and increasing air filtration.
Employer guidance from Washington’s Division of Occupational Safety and Health (DOSH) on ventilation in the workplace includes:
- Ensuring that you have an administrative system in place to prevent sick employees from being present at work.
- Ensuring all HVAC systems are fully functional, especially those shut down or operating at reduced capacity during the pandemic. Also, demand-controlled ventilation may have been adjusted or disabled, hindering the flow of maximum outdoor air.
- Using HVAC system filters with a MERV rating of 13 or higher where feasible. Ninety percent of particles are captured in filters with a MERV rating of 13.
- Inspecting filters and seals monthly, eliminating gaps around filters that allow nonfiltered air to recirculate, and changing filters and cleaning the system as needed.
- Bringing in as much fresh air as possible by increasing the HVAC system’s outdoor air intake and reducing recirculated air, as well as opening windows or other sources of fresh air where possible when weather permits.
- Ensuring that exhaust air is not pulled back into the building’s HVAC air intakes or open windows.
- Turning off ceiling fans or adjusting them to pull air up rather than down to reduce particle dispersal.
- Removing or redirecting personal fans to avoid blowing air from one worker to another.
- Considering the use of portable HEPA fan/filtration systems to increase clean air, especially in higher-risk areas.
- Ensuring that when building maintenance personnel change system filters, they wear appropriate personal protective equipment (PPE), including a respirator such as an N95 filtering facepiece respirator (FFR); eye protection such as safety glasses, goggles, or face shields; and disposable gloves.
- Ensuring that exhaust fans in restrooms are fully functional, operating at maximum capacity, and set to remain on.
DOSH recommends avoiding the use of ionizers or air purifiers that generate ozone, a health hazard itself.
Portable air cleaners
Federal OSHA also recommends considering the use of portable air cleaners with HEPA filters in spaces with high occupancy or limited ventilation in its COVID-19 employer guidance. The EPA states that portable air cleaners with HVAC filters can help reduce airborne contaminants, including viruses, in a building or small space when used properly.
Portable air cleaners are useful in providing additional ventilation when outdoor air ventilation is not possible or preferable due to outside humidity, temperature, or air pollution.
However, air cleaning is not a substitute for source control (the use of masks) and ventilation, according to the EPA. In July, the CDC concluded that portable HEPA air cleaners can reduce exposure to SARS-CoV-2 aerosols in indoor spaces, especially when combined with universal masking.
The EPA cautioned that while bipolar ionization or “needlepoint bipolar ionization” is marketed as a technology that helps remove viruses, including SARS-CoV-2, and facilitates surface disinfection, it is an emerging technology. As an emerging technology, there is little research so far on its efficacy and safety outside of lab conditions. The efficacy and safety of established technology like filtration are well documented.
Portable air cleaners can supplement HVAC systems’ air filtration and ventilation, especially in indoor spaces, where it is difficult to achieve adequate ventilation. However, while using portable air cleaners adds a layer of protection, there is not a consensus that air cleaners are enough by themselves to protect building occupants from COVID-19 exposures.
Researchers at the University of Bristol looked at the existing literature on commercially available HEPA filters and respiratory infections. While they found evidence that indoor air filters did capture bacteria, there was not yet evidence that they could satisfactorily capture viruses like SARS-CoV-2.
Getting assistance from building, facilities managers
The National Institute of Environmental Health Sciences (NIEHS) recommends the use of portable air cleaners to supplement increased outdoor air ventilation and HVAC air system filtration.
In its guidance to portable air cleaners, the NIEHS also offered a series of questions you can ask an HVAC consultant, your building manager, or a facilities engineer about your building’s systems:
- Does the building have a mechanical or natural ventilation system? If it has a natural ventilation system, then you may want to consider the use of portable air cleaners.
- How do the systems work?
- How many air changes per hour of outside air are brought into the building or produced by filters in the HVAC equipment, and where does the outside air enter the building?
- What is the MERV rating of the filters used in this building?
- Can the building’s current systems function with filters rated MERV 13 or higher?
- How often are the filters changed?
- Have renovations changed conditions in some of the rooms, and how is the filtered air distributed to the occupied spaces?
- How many zones and thermostats are used by the HVAC system?
- Are fans set to the “on” position to ensure outside air is introduced to rooms when cooling and heating are not required?
Your options for limiting COVID-19 infections in your workforce follow the traditional industrial hygiene hierarchy of controls: elimination, including ensuring that sick employees or visitors do not occupy your facilities; substitution, such as offering your employees the option to work remotely; engineering controls like increased ventilation and filtration and the use of portable air cleaners; administrative controls like workplace policies requiring face coverings; and PPE, including respirators.
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