Who in the world is installing UV in forced air systems without running an activated carbon filter to remove ozone? The guides I followed when I installed mine called this out multiple times.
All the tech in the world won't change anything if people don't focus on airflow and airchanges. Air needs to move and be replenished with air from the outside. Filters/UV/etc are just a bonus.
Even basic airflow understanding is surprisingly not common knowledge. IE for air to leave a room occupied by humans, then air needs a path into that room too.
I commonly see ceiling exhaust fans in bathroom showers and toilets with windows sealed shut. The door is meant to be closed... so the only gap for air to come into the room is around the door somehow - while the exhaust fan struggles.
I even visited one host who implemented a seal along the bottom of the door because:
1. Shower creates steam and with the above mentioned little airflow, that steam stayed around.
2. So the exhaust fan had to run while they dried themselves with a towel.
3. But they didn't like getting cold feet from the draft of air coming in under the door...
I could not convince them they needed an air intake vent. :-(
Similar but different, a couple of times now I've been in hotel rooms with a bar fridge buzzing away entirely enclosed in a cupboard. Extrapolate that to the hundred rooms or more of the hotel and it is a colossal waste thanks to a "simple" understanding of airflow.
I live in an apartment above a busy road, and my building has no central HVAC. Opening my windows makes the air (much, much) worse.
It took a while to figure this out, so from the ~1.5 years I've lived here, I've accumulated huge, thick coats of brake dust on my windowsills, in my carpets, on the blades of my air-circulation floor... and so on. Probably am half-way to developing COPD.
I do still "replenish air from outside", though! ...through a three-stage filter. (I put an industrial air scrubber on my balcony, and fed the exhaust from it inside through the same kind of doorjam seal you'd use for a portable AC unit.)
I still get noxious fumes coming in sometimes, though. I had to set the thing up on a timer so it wouldn't pull air in during rush hour.
Fair argument, but let’s not forget that indoor air quality, HEPA filters, and upper air UV systems weren’t even allowed to be discussed as solutions to airborne transmission of viruses not that long ago. It was all about masks/no masks, remember? It’s a little unfair to say that things haven’t been studied, when it would have been career damaging to do so until very recently.
No I don't. What I remember is that they said a lot about social distancing and going outside, and for those who do have to be around others, they initially said you gotta wear N95 since ordinary masks aren't very effective, then they said there's a shortage of N95 masks so please just wear normal masks since at least it's better than nothing, and save the N95s for the hospitals and other high-risk settings/workers.
If you remember it differently, please explain what I'm misremembering, because (unlike a sizable fraction of the population) I don't remember hearing anything nonsensical or misleading about masks, especially given the information and resources they had available at the time.
Yep, I agree. Other comments here seem to display a collective amnesia but there was very clearly a mandatory authoritarian single solution to COVID and alternatives were not allowed to be considered even if they were good substitutes. Bringing up alternatives would get you censored or banned or just attacked.
Every jurisdiction had an overreaction fetish. Masks, social distancing and vaccine cards on the left. Ivermectin, detergent pods and intentional exposure on the right.
Maybe there was one with an anti-air filter message. But between New York, the Bay Area, Arizona, Tennessee, Wyoming, London, Frankfurt and New Delhi, I didn’t see it.
this is similar to anti-vax propoganda - setting an ever higher bar and saying we need that first there is no particular reason to think lab tests are not most of what we need.
Double blind studies are helpful when we do not understand they underlying dynamics of a complicated system (like a body) but we want to learn what effect a change has on that system (like a medicine).
If we know pathogens cause disease, and we know filtering removes pathogens from the air (and we can test and verify that) we don't need to run a double blind study to verify they work.
It's the same reason you don't need to run a double blind study on whether seat belts work. We understand the cause and effect of car ejections and windshield/steering wheel impacts on human bodies. Seat belts are designed to mitigate these incidents and are tested and validated in the lab using formal science and engineering.
> It's the same reason you don't need to run a double blind study on whether seat belts work
Actually, seat belts are a weird example. After they were invented, there were more car crashes since people trusted they were protected. Without seat belts people were more cautious. They were a net positive of course, but some different situations/inventions/studies might have effects that are the opposite of what you would expect.
Breathing and sleeping in negative ionized air for 40 years. Just high voltage potential -7 to -10kVDC and spread carbon hairs (better than metal spikes) to launch it.
Walls and floors always have positive charge conducted from the ground outside relative to the air, no sparks means ozone in too small concentrations to worry about. Dust, smoke, bacteria and viruses stick to walls not the inside of lungs and the air is clean and odorless. You can shine a very bright flashlight through it in a dark room and see absolutely no beam. Every so often you sponge off the walls with strong cleaning solution. Latex paint stains easily near the device which is a subtle way of reminding you how germy it really would have been. Use plastic over walls near the device to save yourself some color matching and painting.
Over all these years, the most annoying thing has been other people trying to sell me HEPA filter solutions with screaming fans that need accessory replacement often. They insist I'm killing myself with ozone as a fear tactic. Few people sell just ionizers or sabotage the concept by selling weak/ineffective ones... because HEPA is big money.
Ionizers use tiny energy and no recurring supplies. Just make sure your electronics are grounded well.
I support more research but anecdotally HEPA air filters changed my life. I used to get pretty bad respiratory infections every winter but after getting these that went away. I’m talking the simple kind with basic charcoal prefilter and fiber HEPA filter which are about $150 at most home stores or big box stores. Never used any ionization or ozone. The interesting bit is the newer ones even measure air particulates and have a variable speed option where they will speed up when they detect high pollution… Which turns out is mostly from me cooking.
Your HEPA filters must be real ones. HEPA is just an acronym anyone can slap on anything, there's no accreditation.
Recent testing on the Vacuum Wars channel showed big differences between filters from the vacuum manufacturer and off-brand "HEPA" filters. Probably the same applies everywhere.
I think the next big thing is going to be fixing cooking air pollution. Now that smoking has been in freefall it's becoming increasingly clear that cooking is the next big issue for lung cancers. Especially anything smoky or on a gas stove. It wouldn't be terribly impractical to put a much higher power extraction fan and some side walls to create a kind of fume hood like you'd get in a lab.
For those interested the cheap option is box fan, something like this or duct tape https://a.co/d/3BEXNGp and a hepa filter. Works great and costs about 50 bucks.
In 2023 there was a conference about Chemistry of Indoor Environments (CIE) that looked at the research that was done over a ten-year period; opening presentation:
Generally: avoid any use of electronics to 'do stuff' to the air or pathogens (e.g. UV) and just use high-MERV / HEPA filters, and use an ERV to vent stale air and bring in (filtered, conditioned) outside air.
Even HEPA isn’t a requirement, you just need a high CADR. Doesn’t matter if the filter doesn’t catch a particle on the first pass as long as it does one a subsequent one and the flow rate is high!
I think it's worth mentioning to people that for non-infection purposes, HEPA is honestly not a great idea.
The problem is that such low-porosity filters struggle to even let air move through them. And if you don't move a lot of air, you aren't cleaning a lot of air. At low fan speeds they're effectively placebo for how little they do.
You can get around this by adding yet more powerful fans and cranking up their speed, but then it sounds like a jet engine. Everyone just ends up turning them off (or way down) because they're too noisy - defeating the purpose.
If you just want non-virus stuff (pollen, smoke, dust) then don't go HEPA. Go with something like MERV-13. They come in standard off the shelf furnace style filters. They're way cheaper than HEPA and way better for most use cases.
HEPA only makes sense for something as fine as viruses, or if you only get a single pass to do the filtering. For anything that circulates (like in a house) it makes 0 sense.
There doesn't need to be tests on humans. We have plenty of research showing that viruses harm humans as do small particles in the air this isn't in question at all. These devices have been shown to remove these items from the air using engineering testing based on physics like the electrostatic force and the laws of motion. That they work is not in question, they do filter the air.
The only remaining aspect is how well do they clear air that is constantly getting dirty that has been tested as well, for the most part 6 air changes an hour seems to drastically reduce the particle count.
The problem with medical research "questions" on filtration currently is it thinks random control trials are the gold standard of proof. They aren't physics and engineering tests are a much higher quality of science and evidence. Filters work, respirators do work to remove viruses because we know the size of aerosol they tend to live in (1-5 microns mostly for something like Covid) and how effective the filters are at those particle sizes.
I don't really know if they help to prevent infections but my wife has Long Covid and every time there is too much dust, pollen or smoke around us she gets pretty bad.
So we decided to buy them with little proof after she noticed she feels somewhat better when staying in a room with one. It could even be partially placebo but for the days with too much particles from outside I think it really helps.
Maybe we should rather have a full control of air flows in our home but that would be a huge investment for a very old house, also having air flowing with windows partially open on dry days also seems to help. Humidity ( and certainly mold) also has a clear negative effect so I had to buy a dehumidifier too
35 comments
[ 2.9 ms ] story [ 56.1 ms ] threadEven basic airflow understanding is surprisingly not common knowledge. IE for air to leave a room occupied by humans, then air needs a path into that room too.
I commonly see ceiling exhaust fans in bathroom showers and toilets with windows sealed shut. The door is meant to be closed... so the only gap for air to come into the room is around the door somehow - while the exhaust fan struggles.
I even visited one host who implemented a seal along the bottom of the door because:
1. Shower creates steam and with the above mentioned little airflow, that steam stayed around.
2. So the exhaust fan had to run while they dried themselves with a towel.
3. But they didn't like getting cold feet from the draft of air coming in under the door...
I could not convince them they needed an air intake vent. :-(
Similar but different, a couple of times now I've been in hotel rooms with a bar fridge buzzing away entirely enclosed in a cupboard. Extrapolate that to the hundred rooms or more of the hotel and it is a colossal waste thanks to a "simple" understanding of airflow.
I live in an apartment above a busy road, and my building has no central HVAC. Opening my windows makes the air (much, much) worse.
It took a while to figure this out, so from the ~1.5 years I've lived here, I've accumulated huge, thick coats of brake dust on my windowsills, in my carpets, on the blades of my air-circulation floor... and so on. Probably am half-way to developing COPD.
I do still "replenish air from outside", though! ...through a three-stage filter. (I put an industrial air scrubber on my balcony, and fed the exhaust from it inside through the same kind of doorjam seal you'd use for a portable AC unit.)
I still get noxious fumes coming in sometimes, though. I had to set the thing up on a timer so it wouldn't pull air in during rush hour.
No I don't. What I remember is that they said a lot about social distancing and going outside, and for those who do have to be around others, they initially said you gotta wear N95 since ordinary masks aren't very effective, then they said there's a shortage of N95 masks so please just wear normal masks since at least it's better than nothing, and save the N95s for the hospitals and other high-risk settings/workers.
If you remember it differently, please explain what I'm misremembering, because (unlike a sizable fraction of the population) I don't remember hearing anything nonsensical or misleading about masks, especially given the information and resources they had available at the time.
Every jurisdiction had an overreaction fetish. Masks, social distancing and vaccine cards on the left. Ivermectin, detergent pods and intentional exposure on the right.
Maybe there was one with an anti-air filter message. But between New York, the Bay Area, Arizona, Tennessee, Wyoming, London, Frankfurt and New Delhi, I didn’t see it.
If we know pathogens cause disease, and we know filtering removes pathogens from the air (and we can test and verify that) we don't need to run a double blind study to verify they work.
It's the same reason you don't need to run a double blind study on whether seat belts work. We understand the cause and effect of car ejections and windshield/steering wheel impacts on human bodies. Seat belts are designed to mitigate these incidents and are tested and validated in the lab using formal science and engineering.
Actually, seat belts are a weird example. After they were invented, there were more car crashes since people trusted they were protected. Without seat belts people were more cautious. They were a net positive of course, but some different situations/inventions/studies might have effects that are the opposite of what you would expect.
Walls and floors always have positive charge conducted from the ground outside relative to the air, no sparks means ozone in too small concentrations to worry about. Dust, smoke, bacteria and viruses stick to walls not the inside of lungs and the air is clean and odorless. You can shine a very bright flashlight through it in a dark room and see absolutely no beam. Every so often you sponge off the walls with strong cleaning solution. Latex paint stains easily near the device which is a subtle way of reminding you how germy it really would have been. Use plastic over walls near the device to save yourself some color matching and painting.
Over all these years, the most annoying thing has been other people trying to sell me HEPA filter solutions with screaming fans that need accessory replacement often. They insist I'm killing myself with ozone as a fear tactic. Few people sell just ionizers or sabotage the concept by selling weak/ineffective ones... because HEPA is big money.
Ionizers use tiny energy and no recurring supplies. Just make sure your electronics are grounded well.
Edit: Sorry, you did address that.
> no sparks means ozone in too small concentrations to worry about.
Have you actually measured?
Recent testing on the Vacuum Wars channel showed big differences between filters from the vacuum manufacturer and off-brand "HEPA" filters. Probably the same applies everywhere.
https://www.youtube.com/watch?v=eAIYRykQkMk
* https://www.youtube.com/watch?v=vt0GLbi20Q4
* https://indoorchem.org/publications/
Playlist of the various presentations from the conference:
* https://www.youtube.com/watch?v=J2iHOCI2hz4&list=PLsc2-5fAgM...
Generally: avoid any use of electronics to 'do stuff' to the air or pathogens (e.g. UV) and just use high-MERV / HEPA filters, and use an ERV to vent stale air and bring in (filtered, conditioned) outside air.
Really feels like they went so meta here they lost the plot.
Complaints about fails to catch covid. People are buying air filters to fish out particulate matter not fix a 2022 pandemic.
To say they failed to see the forest for all the trees would be a kindness
The problem is that such low-porosity filters struggle to even let air move through them. And if you don't move a lot of air, you aren't cleaning a lot of air. At low fan speeds they're effectively placebo for how little they do.
You can get around this by adding yet more powerful fans and cranking up their speed, but then it sounds like a jet engine. Everyone just ends up turning them off (or way down) because they're too noisy - defeating the purpose.
If you just want non-virus stuff (pollen, smoke, dust) then don't go HEPA. Go with something like MERV-13. They come in standard off the shelf furnace style filters. They're way cheaper than HEPA and way better for most use cases.
HEPA only makes sense for something as fine as viruses, or if you only get a single pass to do the filtering. For anything that circulates (like in a house) it makes 0 sense.
The only remaining aspect is how well do they clear air that is constantly getting dirty that has been tested as well, for the most part 6 air changes an hour seems to drastically reduce the particle count.
The problem with medical research "questions" on filtration currently is it thinks random control trials are the gold standard of proof. They aren't physics and engineering tests are a much higher quality of science and evidence. Filters work, respirators do work to remove viruses because we know the size of aerosol they tend to live in (1-5 microns mostly for something like Covid) and how effective the filters are at those particle sizes.
Yes that's technically true, but this is just a grant money grab.
It's not a serious attempt to study these things.
I don't really know if they help to prevent infections but my wife has Long Covid and every time there is too much dust, pollen or smoke around us she gets pretty bad.
So we decided to buy them with little proof after she noticed she feels somewhat better when staying in a room with one. It could even be partially placebo but for the days with too much particles from outside I think it really helps.
Maybe we should rather have a full control of air flows in our home but that would be a huge investment for a very old house, also having air flowing with windows partially open on dry days also seems to help. Humidity ( and certainly mold) also has a clear negative effect so I had to buy a dehumidifier too