The model assumes that if you select Terminal Unit or Central/Rooftop Unit, the unit would be operating continuously during school hours. This tool uses data from the National Institute of Standards and Technology. The results are estimates and might not be exact in the real world. Our model assumes an infected occupant (teacher or student) inside a 790 square-foot classroom for 6 hours. The second panel shows the reduction in particles over the 6 hours in the classroom.
The base filter in the “No HVAC” system is no filter, in the “Terminal Unit system” is MERV 6, and in the “Central/Rooftop Unit” is MERV 8. The portable HEPA air cleaner is assumed to be operating at high speed (300 cfm). The exhaust fan is assumed to be 1,200 cfm. The 100% Outside Air option is only available on the “Central/Rooftop Unit” and means that no air is recirculated. All scenarios are compared against a classroom with no central ventilation system with no filter, no HEPA air cleaner, and no exhaust fan. For this model, a “premium” filter is based on one rated for MERV 13 filtration. Note that NIST reported reduction in exposure but reduction in particle levels is reported here. Learn more about HVAC filters and portable air cleaners. Visit Ventilation in Buildings to learn more about MERV ratings.