Study finds gaps in evidence for air-cleaning technologies to prevent infections
46 comments
·August 25, 2025don-bright
vosper
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.
gerdesj
Well you will need a particulate detector to determine the problem and then that will inform your solution.
HocusLocus
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.
0b110907
Do you have a more detailed writeup about how you've set this up?
nom
Can you recommend any devices?
pinoy420
[dead]
jld
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.
valbaca
> It's the same reason you don't need to run a double blind study on whether seat belts work.
We might need some historical investigation into the road that was travelled to get seatbelts to where they are now (physically, legally, and socially). I'm a millennial and I remember growing up where similar arguments were made:
- "If it's my time to go, then it's God's will"
- "It's uncomfortable"
- zero/inconsistent law enforcement
- "If the car rolls over than it can trap you"
To now, where it's entirely automatic and incredibly wild to even suggest being without a seatbelt.
astura
Its crazy, I was born in the early 80s and I never wore a seatbelt until I started driving. As a kid I would ride in a van that didn't even have seats and think absolutely nothing of it.
rootusrootus
I was born in the early 70s and we always wore seatbelts, for as long as I can remember. Though we did routinely ride in the back of the pickup, which isn't something I see happening much today.
slyzmud
> 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.
closeparen
You're not going to spend 100% of your day in the coverage of one of these things, so what's the dose response? How many hours per day of filtered air equals how many fewer infections per year? Does air filtration in your workplace matter at all if you have young kids in school? Does air filtration in a school matter at all if the kids are all together on a poorly ventilated bus for two hours a day?
Seems like some evidence would be helpful.
wahnfrieden
Kids don’t transmit tire and brake dust into my lungs
null
throw0101c
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:
* 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.
rogerkirkness
Yeah the whole 'just use HEPA' has been what's worked for us after about a half dozen different air purifiers of experimentation. I noticed the positive ionization things changed my heart rate variability which was spooky.
o11c
Empirically, the ionizer is good for wildfire season, but the rest of the year HEPA is good.
nextcept
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.
derefr
> be replenished with air from the outside
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.
_carbyau_
> if people don't focus on airflow and airchanges
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.
throw0101c
> * Air needs to move and be replenished with air from the outside. Filters/UV/etc are just a bonus.*
Outside air needs to be filtered otherwise you can bring in pollen and other things (e.g., exhaust/brake dust from cars if near heavy arteries). Avoid UV for residences:
ortusdux
I've been running an airgradient sensor for a year now and as a result I am seriously considering adding a MERV to my HVAC system. Ideally I'd like to get two more sensors (one outside, one in the HVAC ducts) and setup home assistant to govern air exchanges.
jerlam
Yes, there is a whole certification system for measuring how well an air purifier works (CADR - Clean Air Delivery Rate) but consumers are easily distracted and confused by flashy features that promise everything but usually don't do much.
quickthrowman
If by ‘people’ you mean ‘mechanical engineers’, they already do, see ASHRAE 62.1 - Ventilation and Acceptable Indoor Air Quality
https://static1.squarespace.com/static/6320b844c3820725e4d56...
monster_truck
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.
null
bluGill
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.
duffpkg
This is a "metastudy".
Havoc
>analyzed nearly 700 studies
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
DANmode
UV-C / hydroxyl generators or bust
searine
Funded by National Institute for Occupational Safety and Health at the Centers for Disease Control and Prevention aka NIOSH / CDC
jerlam
Which has been completely gutted by the current administration.
aaron695
[dead]
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.