When you talk to Indoor Air Quality (IAQ) most are uncomfortable with UV. Reason being that while you can get rid of viruses, you can also create volatile compounds. Our homes' air is like a soup of natural and synthetic chemicals. From your flooring wear to your decor off-gassing to cooking, there are elements in your air that may be safe as they are, but they can completely change when they hit something volatile like ozone (from cars). Subsequently there can be a chain reaction with other compounds, potentially causing particles in your air that are bad for your health. If you could see that with magical glasses it would seem as if there are fireworks happening in your air triggered by those volatile compounds. So while UV has clear benefits, the byproducts that the lab conditions usually don't catch, make the applications limited.
Interesting, does this also apply to far-UVC (222nm)? Its not surprising that UV would be a catalyst in some undesirable scenario. I'm thinking about toxic residues left by cigarette smoking reacting with household surfaces.
Research suggests that rooms facing the sun (with blinds open) have less bacteria and viruses because it is a disinfectant. I would have to imagine in many homes, UV is somewhat pervasive anyhow.
You can buy HEPA units that have a strip of UV diodes internally after the filter. They’re not overly expensive units. The idea being that the air will pass through:
Charcoal (activated carbon) -> HEPA media -> UV light.
There are some arguments that the UV stage might lower air quality by causing particulates to adhere to room surfaces due to electrostatic charge (i.e. particulate counts would drop rapidly due to particles sticking to walls and furniture, but would then drop off as the charge dissipates and return to room air after the filter is off). I’m not sure how relevant this is - as the filter would catch the particles on the next cycle so I guess it would depend on if the unit is running 24/7 or only some of the time.
Mine failed under warranty and wasn’t replaced with a UV unit due to concerns about Ozone.
My uncle has ozone generators in his home. One of them is industrial strength and he only runs it when he is leaving his house for awhile. Does ozone produce by products? I vaguely recall hospitals used ozone to clean n95 masks.
Ozone is very dangerous. The EPA concluded it poses serious health risks back in 2013 (causes asthma and respiratory harm, short and long term exposure is linked to likely early death, and even linked to cardiovascular problems.)
Cleaning air is simple; you don't need to look to obscure Ozone/UV devices.
For gasses/VOCs, you need a carbon filter. The larger the filter and more air that moves past it, the better. You can grab industrial ones used in greenhouses for ~$150, some brands (LAYOND on Amazon) have cases that make them look alright and make them quiet.
For particulate (dust), a carbon filter works OK but a HEPA filter is better. Get a name brand one (Honeywell) so you're not getting ripped off.
None of that will replace the lack of oxygen, though-so open a window.
Ventilation is critical, lest you get other issues such as mould which is a whole other set of problems in itself.
IKEA do some very good value devices. The Fornuftigs are nice, but quite weak. The Starkvind smart purifiers are better. They’re explicitly not HEPA and aim for less dense media / higher cycles, and they produce generally similar results at lower costs.
(There are some poorly informed reviews online that give a bad review because they’re not marketed as true HEPA filters, but this misses the point of cleaning the air you breathe rather than the air inside the unit. There was a post that corrected these reviews on HN some time back, will try to dig out and update).
> None of that will replace the lack of oxygen, though-so open a window.
I would think that it would be really hard to make any kind of dent in how much oxygen is in the room... wouldn't, by the time you get there, you have long long since died of carbon dioxide poisoning?
Just small increases in the CO2 concentration can cause brain fog and headaches even if you won’t literally die from the room. Normally the feeling of a room being “stuffy” is the first sign. That’s a mere 600ppm where that begins to happen.
Here’s the basic levels of CO2 that are acceptable in a room. I know I get drowsy in rooms without good airflow when in meetings at the office.
And yet in not many years that will be atmospheric levels. This is the element of fossil fuel emissions nobody seems to be discussing, and we don’t know its consequences
In some chess tournaments played remotely they put CO2 sensors in players' rooms and there was a surprisingly big correlation between good and bad form and CO2, to the point that some players started to play with open windows and warm clothes during the winter (for example Jan Krzysztof Duda).
Do you know about carbon filter recycling ? if you pyrolyze the filter would it evaporate the toxic compounds and leave pure carbon lumps ready to reuse ?
N95 masks actually seem like one of the few use cases that make sense, as their composition is well known and they can be easily enclosed. Even when ozone generators work as expected, they can take months to remove odors from spaces.
Most quality whole-home HEPA air filters I know of are available with UV lights that can be added to the mix to further help reduce the viral load in the house. And excessive ozone production is specifically avoided.
For those units, I don't think there's anything to be concerned about here, except the added cost of the UV lighting and what might happen if you (or a technician) were accidentally exposed to the UV lighting during maintenance of the equipment.
IMO, you're going to have to provide some extraordinary evidence if you want to claim UV health risks beyond these two factors.
I have a cheap UV-C lamp that I purchased from ebay. Aside from the danger to your skin and eyes, after running for a few minutes there will be a distinct ozone smell in the room. Once I keept it on for a few hours in a small room (windows and door closed, no people inside). The ozone smell was still there after one week. So at least the lamp that I own would not be suitable for killing virii in indoor environments, unless there is an easy way to convert the ozone back to O2.
Be wary of cheap electronics. E.g. People have been blinded by green laser pointers that convert 1064 nm IR light because of removed ir blocking filters that certain low cost manufacturers remove out of ignorance.
When you mention decor off-gasing, is this the whole thing about off-gasing fire retardant chemical treatments? Or did you mean another source in household stuff?
I haven't seen one of the main arguments against UV efficiency in the context of an HVAC system.
Most common UV solutions simply cannot clean at the speed the air goes through the systems in most buildings. When you have to maintain 6 air changes per hour, the UV solutions are simply not manageable.
There are other limitations but that's the main issue as far as I can tell talking to facility managers.
A room, its occupants and its HVAC is a steady state system, with people emitting virus particles and the HVAC system removing it. The goal is to have the HVAC system remove virus particles quickly enough so that the average particle density is low. You don't need the air coming out of the vent to be completely aseptic; you just need to remove a significant amount of the virus on each pass.
I'm a big fan of using UV for germicidal purposes, but I get extremely concerned when people propose using it in rooms where people are present, like the "just put it high up in a vaulted ceiling" approach discussed in the article. People can get eye damage from halogen lamps with cracked filters in school gymnasiums[1], and those ceilings are generally higher than you'd see in most other types of room.
The potential to end up deploying something that ends up being another asbestos-type "oops, we gave an entire generation cataracts and skin cancer" situation really concerns me. I'd want to see either some very long term research indicating that it didn't happen with far-UV light at all, or that the lights were in fixtures that somehow completely prevented the people below from being exposed.
I find the obsession with having a sterile environment ridiculous. Our bodies themselves are teeming with microbes and viruses, actually our bodies contain more of them than our own human cells.
They play an important role in our digestive system, as well as our metabolism and also keeping our immune system on its guard.
What needs to be done is not to eliminate those actors, but rather to make our bodies resilient to potentiel pathogens.
From a cost-benefit perspective, it feels like most of the things we did to get sterile environments paid off with massive, dramatic drops in mortality and morbidity at every age group and the costs have been a bit of regulatory burden for business and maybe increases in childhood allergies which are likely to be nonfatal and low morbidity? That's a pretty good tradeoff. Even if you think obesity is a phenomenon entirely caused by gut biome and not food, it's still going to be a huge economic positive.
> What needs to be done is not to eliminate those actors, but rather to make our bodies resilient to potentiel pathogens.
If we expose ourselves to these pathogens and wait a few thousand years we might naturally evolve to be resilient.
…otherwise I have no idea what you’re proposing here. You can’t just decide to be resilient. Pathogens kill people. They don’t die because they lacked willpower.
For viruses sure, but other things like air filters make sense. Nothing good comes from breathing combustion engine exhaust or gas stove combustion byproducts.
If you live anywhere near a coal mine or power plant you are also getting a good dose of radioactive dust although I’m not sure a hepa filter is good enough there.
Well now I'm curious. Do you feel the same way about malaria, which kills half a million people a year?
That we shouldn't attempt to remove malaria from our home environment with things like mosquito nets, but rather "make our bodies resilient"?
And... how exactly are we supposed to be making our bodies "resilient" against COVID and the flu and malaria? Seems like you've left out that crucially important detail.
To be clear, the microbiome in our gut has nothing to do with continued exposure to lethal airborne viruses. Sterilizing against one thing doesn't sterilize against everything.
How much energy would it take to fractionally distill air? Ie. Liquify all the air in your house, boil off just the gasses you want, and pipe that back?
Then you could choose for example to have 23% oxygen instead of 20% for a little more alertness, 0 ppm CO2 for a fresh feeling, and get rid of all the trace offgasses, even those that wouldn't be absorbed by activated charcoal.
We did that for my house for a while. It wasn't too expensive, just a couple million a month (after initial one-time costs like buying equipment and building the physical plant on a couple of neighboring acres). But in the end, factoring in plant maintenance and all the employees that it required, my family decided it would be more cost effective to just have weekly shipments of bottled gasses from a scientific supplier.
The problem is enclosed spaces build up pretty high levels of exposure you just don’t find in natural environments. There also tend to have much less of the harmless diversity that outside has.
Yes it is. I used to ventillate my room in Uni when it was way past -20 C outside. As long as you have decent heating it is not a big deal if you do it periodically.
Anecdotal, but: I have found opening windows to be very effective at reducing C02 (as measured with a good sensor) and not very effective at changing the temperature even when it is significantly colder outside than inside. I live in a single family detached house, so I'm not just getting someone elses heat through the walls.
My suspicion is that this has to do with the thermal mass of air versus the thermal mass of the rest of the house - bringing in ~10,000 cubic feet of fresh air with a fan doesnt take long and dramatically improves indoor air quality but doesnt change the temperature much.
Would like to see what my mini office heater can do. The air it outputs is about 75C and I like to think that would kill any viruses, but I guess it depends on whether the split second at that temperature would kill it or not.
* There are a sizable number of fake ones out there.
* There aren't standards and inspection tools for this.
A useful tool would be a UV detector on a stick. You touch it to the ceiling, and it reports on whether there's enough UV in the right wavelengths to kill viruses. The idea is to have emitters which radiate horizontally, with most of the UV up near the ceiling.
You also need a handheld device which checks at eye level for excessive near UV. With both of those, you could quickly tell if a room had reliable virus protection.
All that makes sense - for an ordinary product in an ordinary market.
But this seems like something that could make a serious dent in the covid situation and so government mandates and money could flow and get these much more widely deployed with strong standards.
Also possibly useful military applications. Heck, have the soldiers wear some goggles that have UV protection and just saturate the room in virus killing UV periodically if there’s a suspected biological attack.
Although, why not just put this UV emitter in a big box that has some kind of light filter on it to keep the UV inside rather than worrying about top of the room and so on?
Because you have to push the air through the box with fans. If you can make the ceiling area a kill zone for viruses, ordinary convection effects will push all the air through it regularly.
Also, the UV light involved is very damaging to eyes (causing cataracts and macular degeneration), so it has to be kept entirely contained, yet have all/most of your breathable air pass through it somehow.
They make these for hvac systems, mines installed in the air return, fully enclosed it works well. When the heat or AC isn't in use, I just run the hvac system fan.
Looks like researchers are looking into it "The technique works well, says William Bahnfleth, an architectural engineer at Pennsylvania State University in University Park who focuses on indoor air quality."
I think mechanical ventilation (MV) is less risky and almost as effective in preventing spread of viruses. Probably, coupling MV with a boxed UV lamp (no UV radiation outside the box) would be more effective.
> But the reasoning makes sense: down in that range, the penetration of such light is only a few microns, and it doesn't even get past the dead cells on the surface of the skin and the cornea of the eye!
Ah yes, scientists saying "trust us, it won't harm the body" for the 1000th time, and then after a decade and two they will be proven wrong again.
