Classroom Air Flow and HEPA filters

Brad WalchukUncategorized

You may have seen a recent COVID-10 updatep posted by McMaster online:

The above update confirms:

All McMaster classrooms and lecture halls have been assessed to ensure they meet ventilation requirements as outlined in ASHRAE 62.1. Standard 62.1 outlines minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimize adverse health effects.

Though all of our current operational classroom inventory meets or exceeds Public Health guidelines, McMaster further enhanced our ventilation plan to ensure all lecture theatres and classrooms on campus meet a minimum six equivalent air changes per hour (eACH), a standard considered ideal by Harvard T.H. Chan School of Public Health’s Healthy Buildings for Health guidelines.

This list (last updated January 28) indicates which classrooms and lecture halls on campus meet 6 eACH and actions taken. For classrooms do not meet our minimum standard of six equivalent air changes per hour (eACH), McMaster is:

  • Changing operations or equipment to increase air flow.
  • Equipping the space with appropriate standalone high efficiency particulate air (HEPA) filter units to increase equivalent air changes. The number of HEPA units and sizes were selected for each room in order to meet 6 eACH.

We have confirmed that the HEPAs do have a max speed and low speed setting (some have a 3 speed setting as well). The units need to be at max speed to meet the eACH for the room. When they were installed, the units were defaulted to max speed. There are signs in place indicating that the units should not be moved or turned off (see attached photo). Some instructors have put in microphones to address the noise, Facility Services has also moved units further from podiums to help with noise. They have also asked their custodial staff to turn units on if they are found in the off position.

You can find the eACH of your teaching room on the chart below. All figures should be above 6, especially when filter is running at full strength. If the figure was below 6 eACH, the HEPA filter will bring it to at least 6 eACH