Environmental and HVAC engineers all have heard the phrase – “the solution is dilution” on the best way to handle contaminants. There is even ASHRAE’s 62.1 Standard for determining the minimum outside air required for a space. But, there is another option – measuring things like CO2 and other contaminants and then deciding what the ventilation should be to maintain some level.
A study performed by the Yale Center for Ecosystems and Architecture with several other universities say the second option is better, especially in cities, using plants. Cities have higher outdoor CO2 levels because of population density, cars/trucks, and industry. They argue that plants can directly remove CO2 from the air in the space, reducing it to below outdoor concentrations. Indoor microbe diversity is also improved. So, maybe the solution is a green thumb instead of using that thumb to turn up the outdoor air ventilation rate. – Steve Terry, DTC HVAC & Refrigeration Instructor
