I've been spending a lot of time recently debunking lies about HEPA filters. They have been propagated by school boards and politicians as an excuse to not put them in classrooms. Who started them?
In August 2020, I asked my kid's school to put HEPA filters in the classrooms. I was overruled by a public health official who raised these misguided concerns. For the record, this is no longer the case and the school is making great efforts to make the place safer.
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It's bad actors in IPAC, infectious disease physicians and public health officials who have been controlling the response to this pandemic. They still deny that #COVIDisAirborne . The politicians, media and school boards listen to them.
3/8
There is unanimity amongst engineering organizations, engineers, air quality experts, aerosol scientists and airborne transmission researchers that HEPA filters are extremely beneficial. There is no debate about this, but we have been shut up and shut out of the response.
4/8
In the summer of 2020 ASHRAE stated that aerosol transmission of COVID is significant enough that it needs to be mitigated.
Here is the unheeded call from the Ontario Society of Professional Engineers to mitigate airborne transmission:
Doctors who discuss ventilation or filtration with the media or schools should quote the unanimous opinion of engineering organizations and not offering their own uninformed lies.
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Science tables are ignoring engineers
PH officers/organizations are ignoring engineers
IPAC is ignoring engineers
ID specialists are ignoring engineers
School boards are ignoring engineers
Politicians are ignoring engineers
The pandemic will continue until this stops.
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Many schools have replaced the standard MERV-7 or 8 with MERV-13 filters in the ventilation systems. It's a simple method to filter viruses from recirculated air, but doesn't always work. Here are some issues to consider:
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MERV-13 filters are efficient at filtering out aerosols that contain viruses unlike MERV-8, but they also create a greater pressure drop and restrict flow. This is why ASHRAE recommends units to be rebalanced when filters are upgraded:
In my mind, there are 3 different issues at play: 1. New construction/Renovation - I'm not concerned about this. There will be a lot more research on air quality and health and there is now public awareness about its importance.
1/9
I have confidence that ASHRAE will update the guidelines based on our new societal values and we can make new designs better moving forward.
2. Under-ventilated buildings - many buildings built in the 50s-80s don't have proper mechanical ventilation.
2/9
How do we deal with this? Do we mandate filtration or UVGI? Do we have to demolish and rebuild a significant percentage of our buildings? Do we continue on as in the past? Heat recovery ventilators can be used sometimes, but not always.
3/9
When the novel coronavirus burst onto the scene, it quickly realized that the mighty HEPA filter was one of its greatest foes.
It began an aggressive anti-HEPA filter lobbying campaign with politicians, public health officials and school boards.
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The goal was to spread lies about HEPA filters to ensure it could infect as many kids as possible. These gullible individuals have been doing PR for the virus and the lies need to be put to rest.
2/9
Myth: HEPA filters blow the virus around
Fact: They remove the virus from the air
This is one of the most prevalent lies against HEPA filters. It’s been used by school boards and politicians as an excuse to not put HEPA filters into schools. This myth needs a thorough debunking.
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AEROSOL SPREAD IN A CLASSROOM
The air in a classroom is well mixed. Anyone who is concerned about blowing the virus around needs to know that it's already been blown around. Here's a diagram of what classroom airflow looks like:
I've been asked about sizing a HEPA filter for your home. This is different than sizing one for public spaces with other people.
This does not provide fresh air. Ventilation is required for that. Here are some things to consider:
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WHAT IS YOUR GOAL?
Do you just want to improve the air quality in your house in general or do you want to have a gathering and use the HEPA filter to mitigate risk of COVID transmission? The clean air delivery rate (CADR) for these two goals is very different.