r/) 9/23/2020 Epidemiological summary of COVID-19 cases in Canada - Canada.ca Normal fresh air ventilation trend in HVAC mixed air systems Consideration of normal fresh air intake to COVID cases relationship 2,000 1,800 “A” “B” HVAC maximum fresh air likely HVAC minimum fresh air more likely 90% to 100% fresh air probable Often 10% to 30% minimum fresh air Larger number of COVID cases Lesser number of COVID cases r/) Q) 1,600 ro 0 -c 1.400 0 a. 1,200 0 Qi 1,000 .0 E z::i 800 600 400 200 Canada’s COVID infection graph. Date of illness onset APRIL AVERAGE CANADA LOW/HIGH TEMPERATURES Vancouver, BC: 44 / 56F, (7 / 13C) Edmonton, AB: 31 / 52F, (-0 / 11C) Winnipeg, MB: 32 / 51F, (0 / 11C) Ottawa, ON: 34 / 52F, (1 / 11C) Toronto, ON: 39 / 54F, (4 / 9C) Montréal, QC: 34 / 49F, (1 / 9C) Halifax, NS: 33 / 47F, (0 / 8C) St. John's, NF: 30 / 41F, (-1 / 5C) (Temperature values via tripsavvy) MAY AVERAGE CANADA LOW/HIGH TEMPERATURES Vancouver, BC: 49 / 63F, (9 / 17C) Edmonton, AB: 42 / 64F, (6 / 18C) Winnipeg, MB: 44 / 64F, (7 / 18C) Ottawa, ON: 47 / 67F, (8 / 19C) Toronto, ON: 50 / 66F, (10 / 19C) Montréal, QC: 46 / 63F, (8 / 17C) Halifax, NS: 42 / 58F, (6 / 14C) St. John's, NF: 36 / 51F, (2 / 11C) JUNE AVERAGE CANADA LOW/HIGH TEMPERATURES Vancouver, BC: 54 / 67F, (12 / 19C) Edmonton, AB: 50 / 70F, (10 / 21C) Winnipeg, MB: 56 / 74F, (13 / 23C) Ottawa, ON: 56 / 75F, (13 / 24C) Toronto, ON: 59 / 76F, (15 / 24C) Montréal, QC: 58 / 75F, (14 / 29C) Halifax, NS: 51 / 67F, (11 / 19C) St. John's, NF: 43 / 60F, (6 / 16C) 1) HVAC mixed air fans are more likely to maximize fresh air close to 100% in the seasonal range “A” because the outdoor air day time average temperature is close to the supply fans’ normal low limit set point of 55˚F to 60˚F. 2) HVAC mixed air fans are more likely to minimize fresh air to design minimum fresh air quantities in the seasonal range “B”, as the fresh air “free cooling” is often prevented, as determined by enthalpy comparison or dry bulb fresh air high limits via economiser logic. (Fresh air and return air enthalpies compared or fresh air over about 70˚F reverts fresh air quantity to minimum reducing mechanical cooling energy requirements.) 3) The current position that more fresh air will assist in the reduction of COVID-19 infections seems to be questionable given the infection rate and normal HVAC seasonal fresh air intake as graphed. Other factors seem dominant. 4) Most case studies focus on virus concentrations in the occupied space, but do not quantify virus concentrations in the airflow to and from the HVAC fans. Data is required showing virus concentrations in the occupied space, fresh air, return air as it enters the mixing plenum, in the exhaust air and the supply fans’ discharge. This data is necessary in developing the most effective and most energy efficient plan. 5) It can be argued via some current case studies that there will be no gain in virus transmission reduction by flushing with 100% fresh air over mixed air, but 100% fresh air will increase operating costs and GHG emissions. https:llhealth-infobase .canada .ca/covid-19/epidemiological-summary-cov id-19-cases.html 11.208
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