Back to Basics, Personnel Safety

Back to Basics: Spotlight on Indoor Air Quality

Back to Basics is a weekly feature that highlights important but possibly overlooked information that any EHS professional should know. This week, we examine how to manage indoor air quality.

How well are you managing the indoor air quality in your workspace? The biggest indoor air concerns for decades were exposure to radon, mold, and tobacco smoke. The focus has now shifted to respiratory infections and wildfire smoke.

Is your facility located in a region beset with wildfire smoke? Are you prepared for a triple surge in respiratory infections—COVID-19, influenza, and respiratory syncytial virus (RSV)—anticipated this fall and winter? In its October 28 influenza surveillance report, the Centers for Disease Control and Prevention (CDC) reported early increases in seasonal flu.

The White House recently hosted a summit on indoor air quality that included academics, executives, and current and former government officials.

Dr. David Michaels, former assistant secretary of labor for occupational safety and health under President Barack Obama, moderated the “Panel on Why Improving Indoor Air Quality Makes Good Business Sense.”

“I’m proud to say that OSHA understood from the very beginning that this understanding of COVID spread,” primarily through respiratory droplets and fomites (infectious particles on objects or surfaces), “was inadequate.”

“We learned during the H1N1 pandemic in 2009-2010 that many viruses like coronavirus, like influenza, were spread not just by droplets, but by aerosols, tiny airborne particles.”

The existence of aerosolized SARS-CoV-2 was firmly established in 2020.

Airborne particles “can travel the air far more than six feet in distance, and they can accumulate in the air, leading to greater exposure,” Michaels said at the White House summit.

“This means that respirators like N95s are far superior to surgical masks, and that it’s vitally important to ensure the indoor air we breathe is as virus-free as possible.”

OSHA urged to act

This past spring, a group of public health experts urged the Occupational Safety and Health Administration (OSHA) to establish federal workplace standards for ventilation and other controls like appropriate personal protective equipment (PPE) and physical distancing in anticipation of future surges in COVID-19 infections. The group recommended that OSHA incorporate ventilation and air filtration requirements for indoor work environments into federal standards and the agency’s employer guidance.

This summer, the Lancet COVID-19 Commission’s Task Force on Safe Work, Safe School, and Safe Travel released a report recommending that employers and building owners take steps to reduce COVID-19 transmission that include the following:

  • “Commissioning” or “recommissioning” building systems to ensure that their buildings are operating as designed.
  • Increasing outdoor air ventilation either through greater air exchanges in heating, ventilation, and air conditioning (HVAC) systems or by opening windows to dilute the concentrations of infectious particles in an indoor space. The group recommended four to six air changes per hour to reduce the risk of airborne infectious disease transmission indoors.    
  • Upgrading air filtration in HVAC systems to Minimum Efficiency Reporting Value (MERV) 13 filters or higher in systems that can accommodate high-filtration filters.
  • Supplementing HVAC systems or open windows with portable air cleaners where necessary.

The task force’s recommendations are based on an understanding of the danger posed by virus-laden aerosols.

Evolving science

Many of the recommendations in early COVID-19 guidelines and requirements of the first state-level emergency temporary standards (ETS) were based on the assumption that COVID-19 spread through larger respiratory droplets. However, interventions like clear plastic barriers, which were recommended in early COVID-19 guidelines and early regulations, can actually allow infectious particles to accumulate. When OSHA issued its healthcare COVID-19 emergency temporary standard, the American Industrial Hygiene Association (AIHA) expressed concern about requirements for physical barriers.

The group pointed out to the agency that while barriers might offer a sense of security for workers and members of the public, they effectively decreased the mixing of air in any room where they are erected.

Newer requirements stress the importance of ventilation and air filtration. For example, Oregon’s permanent COVID-19 regulation requires that employers optimize and maintain workplace ventilation systems.

To conform to these updated recommendations and regulations, you will need the services of facilities staff and vendors to properly operate or upgrade HVAC systems.

While hospitals and healthcare facilities may have HVAC systems with components like high-efficiency filters and ultraviolet germicidal irradiation (UVGI) that can effectively eliminate viruses, taking some simple steps may help you prevent or reduce infections in your workplace. These steps include:

  • Letting outdoor air in by opening windows—the easiest way to ventilate indoor spaces,
  • Rearranging office seating to avoid having too many people in the same path of airflow, and
  • Allowing your HVAC systems to run even when buildings are unoccupied instead of shutting down systems on evenings and weekends.

Much of the science around ventilation and infection control predates the COVID-19 pandemic by a century. In the wake of the global influenza pandemic of 1918–1919, the widespread adoption of steam radiator heat enabled building occupants to open windows during winter, diluting the concentration of infectious particles in indoor air.

The CDC now confirms that COVID-19 is spread when someone breathes in small droplets or particles containing SARS-CoV-2, the virus that causes COVID-19.

The Environmental Protection Agency (EPA) explains that when people infected with COVID-19 cough, exhale during exercise, sing, or even speak or breathe normally, they release droplets and particles of respiratory fluids containing the SARS-CoV-2 virus. Unlike droplets that may quickly fall to the ground, very fine particles can continue to spread through the air in an indoor space. Particles can accumulate in spaces with poor ventilation.

The CDC recommends avoiding poorly ventilated spaces. In fact, one of the first documented outbreaks of COVID-19 in the United States was a “superspreading” event in a poorly ventilated space affecting members of the Skagit Valley Chorale in Skagit Valley, Washington. A single member experiencing cold-like symptoms at a March 10, 2020, choir rehearsal spread the disease to 53 members among the 61 attending. Two choir members later died.

Brave new HVAC world

Addressing indoor air quality represents a significant change from “business as usual.” Building ventilation systems have long been designed for comfort and general air quality (removing odors), not the removal of particles from an infectious source, the American Conference of Governmental Industrial Hygienists (ACGIH) points out.

In some buildings, system inlet and outlet placement can lead to a concentrated buildup of infectious particles.

Long before the COVID-19 pandemic, professionals and researchers knew about the link between poorly ventilated indoor spaces and respiratory infections. However, there are indoor air quality issues besides risks of infection. Research has established a link between poor indoor air quality, higher sick leave costs, and lost productivity. Researchers in December 2000 analyzed the sick leave use among employees of a large manufacturer. They found increased sick leave use among workers assigned to poorly ventilated spaces. Their analysis found the employer could have seen net savings of $400 per employee per year by improving ventilation.

Joseph B. Allen, a Harvard public health researcher who spoke at the White House indoor air quality summit, points out that HVAC standards for buildings other than hospitals do not recommend enough air changes per hour to achieve infection control. In a commentary in the Journal of the American Medical Association, Allen recommended increasing the number of air changes (four to six per hour in small spaces like retail shops) through increased outdoor air ventilation, recirculated air passed through a filter with a MERV rating of at least 13, or the use of portable air cleaners with high-efficiency particulate air (HEPA) filters to limit COVID-19 transmission.

OSHA recommends that employers consult a qualified HVAC professional to ensure that building ventilation systems operate optimally. Ventilation and air filtration also are part of the agency’s guidance for employers on mitigating and preventing the spread of COVID-19 in the workplace. Other controls include encouraging and facilitating vaccination and ensuring that workers infected with COVID-19 stay home to eliminate infectious disease risks for others.

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has recommendations for protecting building occupants during COVID-19 surges, including using portable air cleaners. The ASHRAE even offers guidance on protecting commercial building occupants from wildfire smoke.

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 the level of air filtration.

Washington’s Division of Occupational Safety and Health (DOSH) revised its employer guidance on workplace ventilation earlier this year. DOSH recommends that employers and building owners:

  • Change filters and clean ventilation systems as needed, eliminate gaps around filters that can allow nonfiltered air to recirculate, and inspect filters and seals monthly.
  • Use 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.
  • Bring in as much fresh air as possible by increasing the HVAC system’s outdoor air intake and reducing recirculated air or opening windows or other sources of fresh air, weather permitting.
  • Ensure that exhaust air is not pulled back into the building from HVAC air intakes or open windows.
  • Turn off ceiling fans, or adjust them to pull air up rather than down to reduce particle dispersal.
  • Remove or redirect personal fans to prevent blowing air from one worker to another.
  • Ensure that workers changing air filters wear appropriate PPE, including a respirator with N95 filters, eye protection (safety glasses, goggles, or face shields), and disposable gloves.
  • Make sure exhaust fans in restrooms are fully functional, operating at maximum capacity, and are set to remain on.
  • Encourage workers to report ventilation issues and other safety and health concerns.
  • Consider using portable HEPA fan/filtration systems to clean air, especially in higher-risk areas like enclosed smaller spaces with little or no ventilation or capability to provide outside air, but avoid using ionizers or air purifiers that generate ozone, a health hazard itself.

Portable air cleaners

Federal OSHA also recommends using 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 help provide additional ventilation when outdoor air ventilation is not possible or preferable due to outside humidity, temperature, or air pollution.

Whether you’re dealing with wildfire smoke or spikes in respiratory infections, interventions like increased ventilation, high-efficiency air filtration, or even the use of portable air cleaners can improve indoor air quality.

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