CDC Updates Recommendations for Ventilation in Buildings

On March 23, 2021, the Centers for Disease Control and Prevention (CDC) updated their recommendations to improve ventilation in buildings to reduce the spread of COVID-19 and lower the risk of exposure. Protective ventilation practices and interventions can reduce airborne concentration and reduce the overall viral dose to occupants of a building.

COVID-19 viral particles spread between people more readily indoors than outdoors. Even a light wind can rapidly reduce concentrations of the COVID-19 viral particles. The lower the concentration, the less likely the viral particles can be inhaled into lungs, contact eyes and mouth, or fall out of the air to accumulate on surfaces.

The following list of tools can be universally applied across indoor environments. Applying them to different building types, occupancies, and activities under environmental and seasonal changes can be challenging. The specific combination of tools chosen for use at any point in time can change. It will be important to identify which tools are appropriate for each building throughout the year. Further, not all interventions will work in all scenarios.

The list of tools to improve ventilation includes:

• • Increase the introduction of outdoor air:
    • Open outdoor air dampers beyond minimum settings to reduce or eliminate HVAC air recirculation. In mild weather, this will not affect thermal comfort or humidity. However, this may be difficult to do in cold, hot, or humid weather, and may require consultation with an experienced HVAC professional.
    • Open windows and doors when weather conditions allow to increase outdoor air flow. Do not open windows and doors if doing so poses a safety or health risk (e.g., risk of falling, triggering asthma symptoms) to occupants in the building. Even a slightly open window can introduce beneficial outdoor air
  • Use fans to increase the effectiveness of open windows:
    • To safely achieve this, fan placement is important and will vary based on room configuration. Avoid placing fans in a way that could potentially cause contaminated air to flow directly from one person to another. One helpful strategy is to use a window fan, placed safely and securely in a window, to exhaust room air to the outdoors. This will help draw outdoor air into the room via other open windows and doors without generating strong room air currents. Similar results can be established in larger facilities using other fan systems, such as gable fans and roof ventilators.
  • Improve central air filtration:
    • Increase air filtration to as high as possible without significantly reducing design airflow. Increased filtration efficiency is especially helpful when enhanced outdoor air delivery options are limited.
    • Make sure air filters are properly sized and within their recommended service life.
  • Ensure restroom exhaust fans are functional and operating at full capacity when the building is occupied.
  • Inspect and maintain exhaust ventilation systems in areas such as kitchens, cooking areas, etc.
    • Operate these systems any time these spaces are occupied. Consider operating them even when the specific space is not occupied to increase overall ventilation within the occupied building.
  • Generate clean-to-less-clean air movement by evaluating and repositioning, as necessary, the supply louvers, exhaust air grilles, and/or damper settings.

The ventilation intervention recommendations come with a range of initial costs and operating costs, which, along with risk assessment factors, can affect the selection of tools. Consider consulting an experienced heating, ventilation, and air condition (HVAC) professional when deciding on changes to HVAC systems and equipment.

In addition to ventilation improvements, the CDC continues to recommend the layered approach of physical distancing, wearing a face mask, hand hygiene, and vaccination to reduce the spread of COVID-19.

The CDC’s complete list of tools to improve ventilation can be accessed here.

Compliance Perspective

Issue

Each facility should do all that can be done to reduce the spread of COVID-19 and other infectious diseases. As facilities begin to open more freely to visitors, it is a critical time to review your facility’s Infection Control Plan, including ventilation of the building. Although we are seeing a decrease in the number of COVID-19 cases in facilities, likely due to the COVID-19 vaccination and other factors, all facilities must remain vigilant in enforcing their Infection Control Plan.

Discussion Points

• • Review your Infection Control Plan and ensure that it includes discussion on ventilation for your building to reduce the spread of COVID-19 and other infectious diseases.
  • Train all staff on your Infection Control Plan. Ensure that those individuals in your facility with responsibility for building maintenance and ventilation oversight have access to the CDC’s latest guidelines on this topic. Document that these trainings occurred and retain the signed document in each employee’s education file.
  • Periodically audit to ensure that employees are competent in infection control, and that the facility’s Infection Control Plan is being followed at all times. Consider reviewing ventilation requirements, equipment settings, and proper function with an HVAC professional.