It’s no secret that indoor air quality is critical for overall health and wellbeing. Indoor air pollutants can have adverse effects ranging from short-term eye and throat irritation to long-term effects like respiratory disease and even cancer. When it comes to diseases that can be transmitted through infectious aerosols passed through the air, such as SARS-CoV-2, ventilation, filtration, air distribution systems and disinfection technologies have the potential to limit airborne pathogen transmission through the air and thus break the chain of infection.
Decreasing exposure is an important step in diminishing the spread of infectious diseases like COVID-19. Designers of mechanical systems must be aware that ventilation is not capable of addressing all aspects of infection control. Small aerosols may persist in the space, available for inhalation directly or settling onto surfaces, where they can be indirectly transmitted by resuspension or contact with an object (such as a dish or a doorknob) that may be contaminated.
On April 14, 2020, ASHRAE issued recommendations for mitigating infectious aerosols. Some of those recommendations include:
- Improve central air and other HVAC filtration to MERV-13 (ASHRAE 2017b) or the highest level achievable.
- Add portable room air cleaners with HEPA or high-MERV filters with due consideration to the clean air delivery rate (AHAM 2015)
- Bypass energy recovery ventilation (ERV) systems that leak potentially contaminated exhaust air back into the outdoor air supply
- Increase outdoor air ventilation (disable demand-controlled ventilation and open outdoor air dampers to 100% as indoor and outdoor conditions permit)
- Add duct- or air-handling-unit-mounted, upper room, and/or portable ultraviolet germicidal irradiation devices in connection to in-room fans in high-density spaces such as waiting rooms, prisons, and shelters
- Temperature and humidity control (between 40% and 60% Relative Humidity)
- Upper-room ultraviolet germicidal irradiation (with possible in-room fans) as a supplement to supply airflow
- Keep systems running longer hours (24/7 if possible).
- (For Healthcare buildings) Maintain negatively pressurized intensive care units (ICUs) where infectious aerosols may be present.
- (For Healthcare buildings) Maintain rooms with infectious aerosol concerns at negative pressure.
- (For Healthcare buildings) Capture expiratory aerosols with headwall exhaust, tent or snorkel with exhaust, floor-to-ceiling partitions with door supply and patient exhaust, local air HEPA-grade filtration
Design engineers can make an essential contribution to reducing infectious aerosol transmission through the application of these strategies. Managing indoor air to control distribution of infectious aerosols is an effective intervention which adds another strategy to medical treatments and behavioral interventions in disease prevention.