Research Conducted by Associate Professor, Kevin Grosskopf
Balancing Airborne Infection Control and Energy Use in Hospitals
Hospitals are among the most energy intensive buildings in the U.S., averaging between 860-1,450kWh/m2/year, or, approximately 3-times the energy use of comparable office buildings. Nearly one-third of hospital energy consumption is used to maintain climate control and indoor air quality (IAQ) through the use of heating, ventilation and air conditioning (HVAC) systems. In spite of this, hospital acquired infections (HAIs) in the U.S. claim more than 90,000 lives and cost more than $US 20 billion each year.
Accordingly, a study was devised to observe the aerodynamic behavior of bioaerosols under various ventilation regimes in an actual hospital. Specifically, a series of four tests were conducted to map the spatial dispersion of aerosols with respect to particle size, ventilation rate, air pressure differential and door movement between two patient rooms and a corridor. Results indicate that under neutral (non-directional) airflow and a ventilation rate of 2.3-2.5 room air changes per hour (ACH), concentrations of aerosols 0.3-10.0µm were several times ambient levels in both the patient rooms and adjacent corridor. Under 2.5Pa negative (inward) airflow and a ventilation rate of 5.1-5.5 air changes per hour (ACH), containment of aerosol within patient rooms was mostly achieved. However, concentrations of aerosol were reduced on average only 25%-30%, remaining several times higher than ambient. In some cases, concentrations of aerosols ≥1.0μm increased with respect to ventilation rate, possibly as a result of turbulent mixing and subsequent suspension of larger particles.
The results of this study, when compared to other similar studies, may identify optimal levels of ventilation that maximize airborne infection control whilst minimizing energy use particularly in isolation and protective environments.