New Guidance From CDC: Pay Attention to Ventilation

The Centers for Disease Control (CDC) recently updated its guidance “Improving Ventilation in Buildings”. The COVID-19 pandemic led to increased attention to indoor air and methods to reduce the transmission of viruses that cause respiratory infections (Morawska et al., 2021). The updated guidance can assist occupational health professionals (OHPs) who are responsible for employees in indoor workplaces like office settings and enclosed indoor spaces where employees work close together or are in contact with visitors, patrons, clients, patients, or customers.

The CDC recommends three basic strategies. First, ensure that heating, ventilation, and air conditioning (HVAC) system is operating as designed and meeting local codes. OHPs can review the new CDC guidance with the Building and Facilities Manager responsible for the HVAC system. OHPs can inquire about the state of air circulation focusing on code requirements, areas of improvement, and success in increasing the amount of clean outdoor air brought into the workplace without an undue burden or cost. Some workplaces can increase air circulation by opening windows, but it is imperative to check with the building facilities manager.

The second and third strategies center around filtration and virus inactivation. Discuss air cleanliness with the facilities manager. Discuss the methods that remove particles from the air. This is critical for infectious particles such as viruses but can also be beneficial to remove particles from wildfire smoke, allergens, and other pollutants. HVAC systems provide filtration of the circulating air. You can also add filtration systems such as portable high efficiency particulate air (HEPA) filters. It is also possible to inactivate viruses with germicidal ultraviolent systems (GUV). UV systems must be installed by competent and specially trained technicians (see FAQ #7); U. S. CDC, 2023).

The CDC recommends at least five or more air changes per hour (ACH). This is a significant and very specific change. These new recommendations partly come from the Task Force on Safe Work, Safe School, and Safe Travel 2022 report, (Sachs et al., 2022). Improving ventilation reduces the likelihood of infections; however, there are many factors to consider including how many sick people are shedding viruses and how closely they work near other. When airborne viruses are circulating, such as in the winter during flu season, COVID surges, or respiratory syncytial virus (RSV) outbreaks, improving ventilation is associated with reducing absenteeism (Milton et al., 2000).

The new guidance includes a “Cost Considerations” table which assists OHPs and building managers in prioritizing interventions according to cost and location feasibility. This list provides information about up-front costs, ongoing daily costs, ongoing maintenance requirements, and energy usage for a list of nine interventions. The Frequently Asked Questions section delves into questions we all have such as “Can COVID-19 be transmitted through HVAC (ventilation) systems?” and “How long will it take to dilute the concentration of infectious particles in a room once they are generated?.” OHPs should also review the section FAQ #8 on emerging technologies (U. S. CDC, 2023).

Finally, this guidance addresses the use of carbon dioxide (CO₂) monitors. Carbon dioxide is a proxy for exhaled breath and, as such, elevated levels may indicate that levels of fresh air are too low. The CDC provides a CO₂ target of 800 parts per million (ppm). Achieving this target is one piece of information in the complex world of indoor air quality. Asking questions, reviewing this guidance, and partnering with building management professionals are well within the scope of OHPs and should be considered a “best practice” for the pending winter virus season. It can add ventilation, filtration, and virus inactivation technology to their prevention toolbox to reduce respiratory infections such as colds, flu, RSV, and COVID-19.