One concern I've heard about UV (and ionization) stuff is that you're adding 'active chemistry' into your ventilation system, which could possibly cause strange reactions you may not want.
Besides 'bugs' and dead skin, there are are VOCs and other chemicals that we use in our homes: how will those reaction? If these units are new and working properly, things may be fine, but how many homeowners will do (or have someone do) regular inspections/maintenance? Having this stuff in non-residential places may be fine because Facilities has a role in keeping HVAC working: regular people don't do that.
Having good filters (MERV ≥13) will get rid of most of stuff you don't want in a simpler fashion.
Paradoxically, a 'more efficient' filter will generally achieves lower real-world performance (CADR) because the airflow drops so much.
The MERV rating are often hidden, instead you may need to look for numbers from a company-specific rating system like 3M's 'MPR 1900' or Home Depot's (yes, really) 'FPR 10.'[0]
(I almost don't want to include this last paragraph of info, because by sounding like an ad it will automatically 'taint' everything else, but fuck it....)
I find myself generally buying the 3M version (which is ~30% more expensive locally) which I observe has a much higher pleat count. That means more surface area (lifetime) and better pressure drop (airflow). By my math I come out ahead in cost per area of medium, which for me is a better metric than cost per filter.
[0] https://airfiltersdelivered.com/blogs/helpful-tips/merv-mpr-...
Anyone got recommendations for a reputable vendor online? Something other than BezosMart?
It isn't just a backup; you want it there before the expensive fine-grained filter, to catch the big stuff and extend the life of the more expensive filter.
I wouldn't use a prefilter with any real pressure drop thought. Why not? Well...
In theory a two-stage filter is ideal, because you can cycle the filters through: swap the (mostly clean) post-filter over to the pre-filter during filter changes, optimizing both filtration level and using the full capacity of each consumable filter element. This is the procedure when changing the ISS water filters, incidentally.
There's a downside, of course...
Essentially it's the same as series and parallel resistors, so for two filter stages in series (to achieve the same rated pressure drop) you need double the rated size for each of the stages, therefore 4x the total filter area and size. In practice, nobody really wants to install that in their basement.
Some of the Chinese positive pressure systems have seemingly the ultimate low-consumables design: a washable stainless prefilter, washable electrostatic filter, two stages (supports cycling) of HEPA filter, and last a refillable granular activated carbon stage. Spent activated carbon could be used as a soil amendment, or returned to a local facility for regeneration into new activated carbon.
Very low consumables, but very costly up-front.
> When inhaled, ozone can damage the lungs. Relatively low amounts can cause chest pain, coughing, shortness of breath and throat irritation. [0]
[0] https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-...
[0] https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradia...
The article is about KrCl 222-nm lights, which people want because they're safe [1] to shine on people, unlike Hg 254-nm lights.
[1] Probably -- I'd like to seem some specific additional experiments before widespread deployment.
254nm is also not safe.
254nm destroys ozone, interestingly.
240nm and smaller (160nm being the highest producing freq.) produce ozone.
[https://onlinelibrary.wiley.com/doi/full/10.1111/php.13391]
The whole point of using 222nm is that it doesn't cause effects on either the eyes or the skin. Consequently, you can use it at higher concentrations without worrying about the leakage.
The issue, as I understand it, is simply that we don't have a decent LED monochomatic source. All of the currently available sources have broad spectrums that have to be filtered out.
Where did you find that 185nm number? Everything I see on google says ~250nm, not to mention the original post is about 222nm UV.
Smaller than 240nm creates it, to various degrees, with the ideal frequency being 160nm. 185nm is 'produces a noticeable amount'.
[https://onlinelibrary.wiley.com/doi/full/10.1111/php.13391]
UV units intended for installation in return or supply ducts are snake oil. A waste of electricity and money (the bulbs have a pretty finite lifespan.) The velocity of air in most ducts is such that anything flying by wouldn't be sterilized, and you can just install a large air filter (like the Aprilair 413 others have mentioned) and it'll bring a lot more benefits to the table, namely much better reduction of dust.
The greatest problem with indoor air quality is offgassing of VOCs and other pollutants from construction materials, furniture, electronics, etc.
If you want the best indoor air quality: install a large filter like the Aprilair or some equivalent, an air exchange device, and if you have a gas stove/oven, switch that to electric.
If you just do the simple thing and point the lights in a self-facing ring in the duct, no, they will not work. The trick is to beam the light down the incoming pathway to drastically-increase the exposure time. Clean reflective surfaces in the ducting to even out the photon flux density will greatly help with this.
https://www.amazon.com/Blue-Tube-UV-Light/dp/B00D48XDO0/
Thought it might be applicable to computers, but realized that UV breaks-down PLASTICS as well, which is why you mostly find in ducting.
Very cool stuff if you're into clean/sterile living.
Note: Most of the dust in your home is comprised of human skin. Unless you've had an industrial vacuuming, other people's skin is moving around your house or gumming up the walls of your ducts. UV lights (and chemicals) are the only way to break that shit down.