1/ #VENTILATION is a key factor in #SafeSeptember for #onted. In this thread I'll cover:
🔸My immediate 3 asks of @sfleece and @fordnation
🔸A suggested room-by-room assessment and implementation methodology
🔸Who to follow
🔸My immediate 3 asks of @sfleece and @fordnation
🔸A suggested room-by-room assessment and implementation methodology
🔸Who to follow
2/ My immediate asks of Ontario:
1⃣ Update the Guide to Reopening Ontario's Schools to add #ventilation, currently absent. I recommend using Schools for Health: Risk Reduction Strategies for Reopening from Harvard School of Public Health schools.forhealth.org/risk-reduction…
1⃣ Update the Guide to Reopening Ontario's Schools to add #ventilation, currently absent. I recommend using Schools for Health: Risk Reduction Strategies for Reopening from Harvard School of Public Health schools.forhealth.org/risk-reduction…
3/
2⃣ Also update the Guide to Reopening Schools to reflect current knowledge regarding the relative importance of airborne transmission of COVID-19 compared to surface transmission.
2⃣ Also update the Guide to Reopening Schools to reflect current knowledge regarding the relative importance of airborne transmission of COVID-19 compared to surface transmission.
4/ Final immediate ask of #Ontario:
3⃣ Require that each school room be *measured* for occupant spacing and outdoor air ventilation. Prior to occupancy, each room should have a maximum COVID-19 occupancy posted on the door, with operational requirements of the room,
3⃣ Require that each school room be *measured* for occupant spacing and outdoor air ventilation. Prior to occupancy, each room should have a maximum COVID-19 occupancy posted on the door, with operational requirements of the room,
5/ such as placement of portable air cleaner and speed setting, window or ceiling fans on/off.
This must be done PRIOR to occupancy. Some rooms may end up with a temporary occupancy of 1 or 2 people if a ventilation system is broken.
This must be done PRIOR to occupancy. Some rooms may end up with a temporary occupancy of 1 or 2 people if a ventilation system is broken.
6/ Here is a possible methodology to ensure school room risk from airborne transmission is reduced.
Steal it, improve it!
🔸Examine all central equipment and maintain, repair, upgrade, and measure:
🔸Tighten fan belts (increases air flow), fully open outdoor air dampers,
Steal it, improve it!
🔸Examine all central equipment and maintain, repair, upgrade, and measure:
🔸Tighten fan belts (increases air flow), fully open outdoor air dampers,
7/ install better filtration (MERV-13).
🔸After the repairs and upgrades, measure the airflows to determine the maximum actual outdoor air volume being supplied.
🔸For exhaust-only systems, the same applies but there is no filtration, and only measure the exhaust air flow.
🔸After the repairs and upgrades, measure the airflows to determine the maximum actual outdoor air volume being supplied.
🔸For exhaust-only systems, the same applies but there is no filtration, and only measure the exhaust air flow.
8/
With the central systems known, do a room-by-room physical assessment:
🔸Measure room dimensions. Calculate floor area and room volume.
🔸Photograph all walls and ceiling. Determine all HVAC equipment present.
With the central systems known, do a room-by-room physical assessment:
🔸Measure room dimensions. Calculate floor area and room volume.
🔸Photograph all walls and ceiling. Determine all HVAC equipment present.
9/
🔸*Measure* the air volume rate entering and leaving from all supply air diffusers, return air grills, exhaust fan openings.
🔸Examine & photograph all windows. Determine current and maximum possible open area and area orientation (h vs w), mention outdoor air concerns,
🔸*Measure* the air volume rate entering and leaving from all supply air diffusers, return air grills, exhaust fan openings.
🔸Examine & photograph all windows. Determine current and maximum possible open area and area orientation (h vs w), mention outdoor air concerns,
10/ and what repairs are needed (are window cranks missing?)
🔸For rooms served by central systems, use the measured air flows with engineering calculations to determine the outdoor air supplied to the room. Consider using a tracer gas (CO2) as a proxy in some situations
🔸For rooms served by central systems, use the measured air flows with engineering calculations to determine the outdoor air supplied to the room. Consider using a tracer gas (CO2) as a proxy in some situations
11/
🔸Determine occupant capacity based on minimum allowable proximity, accounting for built-in and movable furniture. Should be 2 meter radius, don't lower until public health guidance & science allows it.
🔸Determine occupant capacity based on minimum allowable proximity, accounting for built-in and movable furniture. Should be 2 meter radius, don't lower until public health guidance & science allows it.
12/
🔸Given the room dimensions, determine the minimum outdoor air requirements by ASHRAE Standard 62.1 for different occupancy scenarios: ASHRAE default, actual typical for the room (almost always higher than ASHRAE), and maximum occupancy (fire or structural limit).
🔸Given the room dimensions, determine the minimum outdoor air requirements by ASHRAE Standard 62.1 for different occupancy scenarios: ASHRAE default, actual typical for the room (almost always higher than ASHRAE), and maximum occupancy (fire or structural limit).
13/
🔸Translate the volume of outdoor airflow into air changes per hour for the room. Should be approx 3 ACH. Current suggested COVID-19 ventilation by @ShellyMBoulder is around 6 ACH, or approx double the ASHRAE amounts:
🔸Translate the volume of outdoor airflow into air changes per hour for the room. Should be approx 3 ACH. Current suggested COVID-19 ventilation by @ShellyMBoulder is around 6 ACH, or approx double the ASHRAE amounts:
14/
🔸Check measured outdoor air volume against various required amounts, and improve:
🪟Under some ACH threshold (TBD) or with natural/exhaust-only ventilation, select a portable HEPA air cleaner. Calculator here:
🔸Check measured outdoor air volume against various required amounts, and improve:
🪟Under some ACH threshold (TBD) or with natural/exhaust-only ventilation, select a portable HEPA air cleaner. Calculator here:
15/
🪟Consider box fans in windows (best practice of pointing in or out or both, and/or taping a furnace filter to inlet still TBD) to force air changes and filter pollen/pollutants from outdoor air. Natural ventilation from windows is NOT reliable!
🪟Consider box fans in windows (best practice of pointing in or out or both, and/or taping a furnace filter to inlet still TBD) to force air changes and filter pollen/pollutants from outdoor air. Natural ventilation from windows is NOT reliable!
16/
🔸Determine maximum occupancy given all factors. Be open about how it is determined - it's not a hard limit, though if equipment is inoperable some rooms may only be suitable for a single occupant.
🔸Determine maximum occupancy given all factors. Be open about how it is determined - it's not a hard limit, though if equipment is inoperable some rooms may only be suitable for a single occupant.
17/
🔸Post a sign on the door indicating maximum COVID-19 occupancy and indicate how the room is to be operated:
-Door, windows open/closed
-Fans on/off
-Portable air cleaner settings and location
-Who to contact for questions/issues
🔸Post a sign on the door indicating maximum COVID-19 occupancy and indicate how the room is to be operated:
-Door, windows open/closed
-Fans on/off
-Portable air cleaner settings and location
-Who to contact for questions/issues
18/
🔸Place/install an inexpensive temperature/RH/CO2 meter in the room along with recommended limits and actions to take.
As temperatures fall, further decisions and actions will be needed to address relative humidity and temperature.
🔸Place/install an inexpensive temperature/RH/CO2 meter in the room along with recommended limits and actions to take.
As temperatures fall, further decisions and actions will be needed to address relative humidity and temperature.
19/ After the immediate needs are taken, the capital repair planning can be started. The photographs and measurements will be valuable.
Let's make permanent changes. Improved indoor air quality improves many aspects of health and performance.
Let's make permanent changes. Improved indoor air quality improves many aspects of health and performance.
20/ There will be increased energy use with proper ventilation. Thankfully there are many ways to address energy and emissions, so don't let that get in the way of action. The many benefits of improved indoor air quality are worth it.
21/ Need more technical detail? ASHRAE is the place. They have made relevant standards available online for free! Check it out: ashrae.org/technical-reso…
22/ ASHRAE continues to update its COVID-19 resource page. Deep link to Schools and Universities section: ashrae.org/technical-reso…
23/ Some clarifying information.
When talking about ventilation in this context, it's outdoor air volumes provided, in cubic feet per minute or liters per second. (5 L/s approx = 10 CFM)
When talking about ventilation in this context, it's outdoor air volumes provided, in cubic feet per minute or liters per second. (5 L/s approx = 10 CFM)
24/ While a "stuffy" room is an indication of poor indoor air quality, a stuffy room can feel much better with A/C, which removes moisture and moves the air around - but without outdoor air and filtration, it's still just as unhealthy as before.
25/ more to come...
26/ Some FAQ's.
💬Why not install HEPA filters?
If it even fits, too much pressure drop, causing large airflow reduction (bad). A MERV-13 filter is kind of like an N90 mask (pretty good!) & is good balance between pressure loss and filtration. HEPA more like N100 mask.
💬Why not install HEPA filters?
If it even fits, too much pressure drop, causing large airflow reduction (bad). A MERV-13 filter is kind of like an N90 mask (pretty good!) & is good balance between pressure loss and filtration. HEPA more like N100 mask.
27/ 💬How does more frequent filter changes help?
Filters are often changed out when the pressure drop reaches a set amount. Following the fan performance curve, the flow reduces as the resistance increases. Change out earlier to have less pressure drop.
Filters are often changed out when the pressure drop reaches a set amount. Following the fan performance curve, the flow reduces as the resistance increases. Change out earlier to have less pressure drop.
28/ 💬My classroom doesn't even have an HVAC system!
Heating: Yes
Ventilation: Yes, but might be exhaust-only, with makeup air coming in through cracks or a makeup air system. Very old schools had natural ventilation (chimney effect) but (should) be using exhaust fans now.
Heating: Yes
Ventilation: Yes, but might be exhaust-only, with makeup air coming in through cracks or a makeup air system. Very old schools had natural ventilation (chimney effect) but (should) be using exhaust fans now.
29/ Compare: many homes have no (outdoor air) ventilation system at all! In 2000's most have a primary exhaust ventilation fan, supposed to run 24h/day. More recently we finally have effective and energy efficient ventilation systems like HRVs in homes.
30/ 💬My school is too old!
I'd be more concerned about some schools designed to 1980's ventilation standards, caused sick building syndrome. Seems we're coming around back to 1900-1940's levels by recommending double the ASHRAE minimum for optimal health.
I'd be more concerned about some schools designed to 1980's ventilation standards, caused sick building syndrome. Seems we're coming around back to 1900-1940's levels by recommending double the ASHRAE minimum for optimal health.
31/ Some more interesting history of older schools in this September 1999 ASHRAE Journal article:
32/ 💬The school board says "all HVAC equipment has been assessed to ensure it is operating as designed"
Ask:
1) which design, 1980's?
2) how do you know, was anything measured?
3) are there records for proof?
Ask:
1) which design, 1980's?
2) how do you know, was anything measured?
3) are there records for proof?
33/ 💬Tell me more about air cleaners
This thread by Jose-Luis Jimenez. Even includes a link to a sizing calculator for classrooms👉
This thread by Jose-Luis Jimenez. Even includes a link to a sizing calculator for classrooms👉
34/ Ventilation is NOT a substitute for lack of masks and physical distancing! Make indoors be more like outdoors in terms of air quality. Otherwise, poor ventilation increases risk.
35/ In safety language, ventilation is an engineering control. Masks are normally last resort PPE, but masks are also a form of source control, and so masks can be considered an engineering control too. Require masks in schools!
36/ PEOPLE TO FOLLOW on ventilation/air quality - so much to learn!
Dr. Shelly Miller @ShellyMBoulder;
Jose-Luis Jimenez @jljcolorado;
Dustin Poppendieck @Poppendieck;
Joseph Allen @j_g_allen;
Marina Eller Vance @marinavance;
Linsey Marr @linseymarr;
Dr. Richard Corsi @CorsIAQ
Dr. Shelly Miller @ShellyMBoulder;
Jose-Luis Jimenez @jljcolorado;
Dustin Poppendieck @Poppendieck;
Joseph Allen @j_g_allen;
Marina Eller Vance @marinavance;
Linsey Marr @linseymarr;
Dr. Richard Corsi @CorsIAQ
37/
This is an opportunity to begin making schools healthier, where disease is prevented rather than incubated, and indoor environmental quality allows students to reach their full academic potential.
Hey @fordnation want to academic scores improve?
Fix our schools.
This is an opportunity to begin making schools healthier, where disease is prevented rather than incubated, and indoor environmental quality allows students to reach their full academic potential.
Hey @fordnation want to academic scores improve?
Fix our schools.
This is a handy decision tree for just the ventilation part from Harvard Healthy Buildings for Schools. Still need masks for source control, and distancing.
