Back to Basics is an article series that highlights important but possibly overlooked information facilities management professionals should know.

Now that fall has arrived, are you ready for this year’s winter respiratory disease season?

The Centers for Disease Control and Prevention (CDC) predicts that COVID-19, influenza, and respiratory syncytial virus (RSV) infections will lead to a similar or lower number of combined peak hospitalizations this winter than the 2023-2024 season. The CDC’s predictions are based on expert opinion, historical data, and scenario modeling conducted by its Center for Forecasting and Outbreak Analytics for COVID-19, influenza, and RSV.

However, there’s inherent uncertainty in any long-range scenario. Factors that could drive higher rates of serious illness and hospitalizations include the following:

• A new COVID-19 variant with an increased ability to evade the body’s prior immunity or a new variant associated with higher clinical severity.
• An influenza subtype with more severe outcomes.
• A lower-than-projected uptake of the COVID-19 vaccine, the seasonal influenza vaccine, or RSV vaccines and immunizations.
• A lower effectiveness against hospitalization for the 2024–2025 COVID-19 vaccine than the 2023–2024 vaccine.
• A lower seasonal influenza vaccine effectiveness against hospitalization than projected.

There are no federal standards for infectious diseases in the workplace. The burdens of a severe respiratory disease season would show up in lower productivity and higher health insurance claims.

Could improved ventilation and air filtration ease the burden of respiratory diseases?

Occupational and public health researchers and the heating, ventilation, and air conditioning (HVAC) industry have long been interested in indoor air quality (IAQ). The HVAC industry’s primary concerns, however, are occupant comfort and system efficiency.

Decades before the COVID-19 pandemic, researchers knew of a link between poorly ventilated indoor spaces and respiratory infections. They also established links between poor IAQ, higher sick leave costs, and lost productivity. Twenty years before the emergence of SARS-CoV-2, researchers analyzed sick leave use among employees of a large manufacturer. They found increased sick leave use among workers assigned to poorly ventilated spaces. Their analysis concluded that the employer could see a net savings of $400 per employee per year by improving ventilation.

Before the pandemic, the American Industrial Hygiene Association (AIHA) formed an Indoor Environmental Quality Global Alliance (IEQ-GA) with other groups to serve as a platform for exchanging indoor environmental knowledge and information and promoting education and research into health and indoor environmental quality. Indoor environmental quality includes air quality, damp conditions, and lighting.

Legionnaires’ Disease—Beyond Seasonality

Any time of year, your employees could face risks from Legionella, the bacterium that causes Legionnaires’ disease, a serious and potentially fatal lung infection, and Pontiac fever, a less serious infection with milder symptoms similar to seasonal flu.

Legionnaires’ disease got its name after a previously unknown strain of bacteria led to a respiratory disease outbreak at a state American Legion convention in Philadelphia in summer 1976. The Legionella bacterium was identified the following year.

Legionella can show up in a building’s water systems. In 2019, Ford Motor Company reported trace amounts of the Legionella bacterium in the water system at the company’s Rouge plant in Dearborn, Michigan.

Legionella growth occurs when water disinfection systems fail, external changes like nearby construction affect water quality in a building, or water temperatures aren’t cold or hot enough to prevent bacterial growth.

Preventing Legionnaires’ disease or Pontiac fever outbreaks requires you to regularly perform risk assessments of your buildings’ systems.

Steps that facilities or workplace safety and health managers can take include:

• Evaluating a water system’s susceptibility to Legionella growth and amplification,
• Prioritizing corrective actions for or improvements to systems found to be at high risk, and
• Validating the effectiveness of control measures.

COVID-19 and Its Aftermath

While severe influenza outbreaks occasionally led to concerns about IAQ and disease transmission, the COVID-19 pandemic raised those concerns to new levels because no vaccines were available at the start of the pandemic.

During the third year of the pandemic, a group of public health experts urged the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) to develop standards to improve IAQ and protect workers and building occupants from inhalation exposure.

In the report “Getting to and Sustaining the Next Normal: A Roadmap for Living with COVID,” the group laid out a series of goals for the CDC, the EPA, OSHA, and the National Institute for Occupational Safety and Health (NIOSH). They emphasized the risks posed by the aerosol transmission of SARS-CoV-2, which causes COVID-19. They recommended a layered approach to worker safety and health that included effective ventilation and air filtration and appropriate respiratory protection.

They also called on OSHA to incorporate ventilation and air filtration requirements for indoor work environments into federal standards and employer guidance to prevent the transmission of airborne infectious diseases like COVID-19 and seasonal influenza.

The group even suggested implementing new respiratory viral illness recordkeeping and reporting requirements, including employer reporting of respiratory viral clusters and outbreaks in their workplaces.

In 2022, a private “Safe Work, Safe School, and Safe Travel” task force recommended that building owners begin taking four steps to address SARS-CoV-2 infection risks in schools and workplaces: verifying that building systems are performing as designed, increasing outdoor air ventilation, upgrading air filtration, and deploying portable air cleaners as needed. The group’s recommendations sought to address the role of virus-laden aerosols in COVID-19 transmission.

At the beginning of the pandemic, epidemiologists and infectious disease experts assumed COVID-19 was primarily transmitted by airborne “droplets,” which prompted their 6-foot “social distancing” recommendations. Researchers went on to find infectious aerosol particles beyond 6 feet.

The Safe Work, Safe School, and Safe Travel task force went on to recommend stronger ventilation and filtration targets in building standards.

How much ventilation is enough? Last year, the CDC updated its “Ventilation in Buildings” guidelines, encouraging employers and building owners to aim for five or more air changes per hour of clean air to help reduce the number of bacteria and viruses in the air.

In addition to recommending five or more air changes per hour, the CDC recommended using Minimum Efficiency Reporting Value (MERV)-13 filters or better and performing post-occupancy flushing of building air. The updated guidelines also include a discussion on whole-room ultraviolet germicidal irradiation (UVGI), sometimes known as “Far UV.”

MERV-13 filters must be compatible with a building’s systems but may be helpful when ventilation options like enhanced outdoor air delivery are limited. The use of portable or built-in high-efficiency particulate air (HEPA) fan/filtration systems, known as “air cleaners” or “air purifiers,” may aid central HVAC systems in curtailing aerosol transmission. Do-it-yourself (DIY) air cleaners like the “Corsi-Rosenthal box,” a cube made up of MERV-13 (or better) filters as the cube’s sides and bottom and a 20-inch box fan attached on top, may reduce COVID-19 transmission, but the CDC considers DIY solutions only appropriate during emergencies or for short-term use. The CDC recommended obtaining commercial air cleaners as a permanent, long-term solution.

UVGI, sometimes referred to as “GUV,” may offer a supplemental treatment to inactivate airborne viruses, such as SARS-CoV-2.

In summer 2023, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) published its Standard 241, “Control of Infectious Aerosols.” The ASHRAE is a professional society that sets HVAC standards for the industry. The industry standard covers aspects of air system design, installation, operation, and maintenance, including requirements for an infection risk management mode; an equivalent clean airflow rate target per occupant of pathogen-free airflow to reduce the risk of infection; the use of filtration and air cleaning (such as HEPA filters, air ionizers, or UV lights) to cost-effectively achieve equivalent clean airflow requirements; and assessment, planning, and commissioning.

Dr. David Michaels, former assistant secretary of labor for occupational safety and health under President Barack Obama, has been vocal about IAQ. In 2022, he moderated a “Panel on Why Improving Indoor Air Quality Makes Good Business Sense” at a White House summit on IAQ.

Joseph B. Allen, a Harvard public health researcher, spoke at the same summit, suggesting that the HVAC standards for buildings other than hospitals don’t recommend enough air changes per hour to achieve infection control. In a published commentary, he recommended increasing the number of air changes through increased outdoor air ventilation, passing recirculated air through a filter with a MERV rating of at least 13, and using portable air cleaners with HEPA filters to reduce respiratory disease transmission.

How Can You Manage Indoor Air Quality?

So, being mindful of the hazards posed by respiratory diseases like COVID-19, influenza, and RSV, what steps should you take to improve IAQ? How can you protect the most vulnerable among an aging workforce?

Steps you can take to achieve adequate ventilation and air filtration include:

• Increasing your HVAC system’s outdoor air intake and reducing the air recirculated to bring in as much fresh air as possible.
• Opening windows or other sources of fresh air when possible when weather and outdoor air conditions permit.
• Ensuring all HVAC systems are properly maintained and fully functional.
• Determining whether demand-controlled ventilation has been adjusted or disabled, which could hinder the maximum flow of outdoor air.
• Using filters with a MERV rating of 13 or higher when feasible. Some systems may not support or need adjustment to support higher-filtration filters. Ninety percent of particles are captured in filters with a MERV rating of 13.
• Inspecting filters and seals monthly, ensuring gaps around filters that could allow nonfiltered air to recirculate are eliminated, changing filters, and cleaning the system as needed.
• Ensuring exhaust air isn’t pulled back into the building’s HVAC air intakes or open windows.
• Turning off ceiling fans or reorienting fans to pull air up rather than down, thereby reducing infectious particle dispersal.
• Considering the use of portable HEPA-equipped air cleaners or purifiers to increase clean air, especially in higher-risk areas.
• Ensuring exhaust fans in restrooms are fully functional, operating at maximum capacity, and set to remain on.

Public health experts are predicting a rate of hospitalizations from respiratory infections like or lower than last year’s. However, several factors involving vaccine uptake, vaccine effectiveness, and viral mutation could change that. If so, implementing targeted IAQ practices could reduce the levels of infectious particles in your facilities.

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