Disabling demand-controlled ventilation
To save energy, some systems monitor building occupancy based on carbon dioxide levels, which rise when we exhale. When fewer people are in the building, the system reduces the rate of outdoor air. “It’s a way to stop ventilating the space to save money,” said Richard Corsi, incoming dean of the College of Engineering at University of California, Davis. “But after people leave an area, we need to continue to ventilate so we can purge the space of any aerosol particles left in the air.”
Increasing outdoor air
Air quality experts recommend adjusting outdoor air dampers, which are movable plates that can bring in more outside air. This isn’t advised in communities with poor outdoor air quality, such as areas with active wildfires.
Don’t be intimidated when asking about ventilation systems. A company that has done the work will have answers at the ready, and the right answers will be obvious. Recently I suggested that my friend ask his gym what it had done to improve ventilation. He is vaccinated and only goes to the gym when it’s not busy, but the reply was encouraging
“We have increased the heating ventilation air conditioning (HVAC) filters to hospital-grade MERV 13,” they wrote. “And opened outdoor HVAC dampers to achieve a higher level of air exchange in the center.”
Can the windows be opened?
Some older buildings and classrooms may not have modern ventilation systems, but simply opening windows can improve air quality. A recent study of infected college students in an isolation dormitory at the University of Oregon found that opening a window could reduce the amount of coronavirus in a room by half.
While opening a window can help, the effect is greater if you can cross ventilate by opening windows on different sides of the room. Open windows aren’t practical during cold weather or in areas with poor outdoor air quality. Adding box fans to windows and turning on exhaust fans in kitchen and bathroom areas can also improve ventilation in homes and in buildings without modern systems.
What is the air change rate?
The air changes per hour, or ACH, number is the industry standard to indicate how often the air in a room is replaced by outdoor air. (Cleaning the air with filters can create the equivalent of air change.) While some experts suggest four to six air changes per hour (that’s fresh or clean air every 10 to 15 minutes), many buildings fall short of that standard. It’s recommended that schools have an ACH of at least 3, but many classrooms are closer to 1.5, experts say. Airplanes and newer hospitals may have anywhere from 10 to 20 air changes per hour. Air change rates or their equivalent can be improved by upgrading the overall ventilation system or filters, increasing the amount of outdoor air (by opening windows or ventilation dampers), adding exhaust fans or by adding portable air filters. If your workplace is decided whether or not to buy an air purifier, this article may help.