Since the COVID-19 pandemic hit North America last February, building IAQ has come into an entirely different focus. A flurry of virus safeguards have been added to commercial building indoor air quality (IAQ) strategies. Now the question arises whether one safeguard is enough.

The most popular strategies for mitigating airborne pathogens have been outdoor air dilution, various media filter improvements ranging from MERV 13 to high efficiency particulate arrestance (HEPA), off-hours building purging, ultraviolet germicidal irradiation (UVGI), and ionization. Building operators frequently choose one of the above methods; however, the question arises whether a better strategy is to combine two or more methods. A better building environment might be established by employing any of the above methods and then supporting it with outdoor air increases for dilution. The reasoning is based on the fact that most methods can stop working due to equipment failure, poor maintenance, or human intervention errors.