Contra Binder on far-UVC and filtration
Apr. 27th, 2026 08:00 am![[syndicated profile]](https://www.dreamwidth.org/img/silk/identity/feed.png){kind=small}
jkaufman_feedDamon Binder recently wrote up an argument for prioritizing air filtration over far-UVC for pathogen control:
UVC and filtration are close substitutes—both deliver effective air changes per hour, both reduce airborne pathogen concentrations by the same amount per eACH—and on current pricing, filtration is cheaper.
There's a lot of good stuff in his analysis, but I see [1] three considerations that really change the bottom line:
- Cost is actually much lower.
- Noise is a serious issue.
- Performance is dramatically higher in larger rooms.
Cost is straightforward. Binder priced far-UVC based on the high-quality Care222 lamp with the Krypton-11 at $2,500, but there's a much cheaper option, the Aerolamp at $500. It's also moderately higher output.
Binder analyzes a 30m2 room with a 2.5m ceiling. I'll assume this means 6x5x2.5. If I configure Illuminate with an Aerolamp in one corner pointed 0.5m above the far corner the installation is within TLVs and I get a median effective number of hourly air changes (eACH) of 11.6. The lamp degrades approximately linearly over Binder's 11,000 hour evaluation period down to 70% capacity, so we're averaging an eACH of 9.8. Over that time you're paying $500 for the lamp and $16.50 for the electricity (0.01kW * 11,000hr * 0.15 $/kWh) for a 5-year $/eACH of $53. Adding this to the best-performers from Binder's table, the Aerolamp is now the same cost as the cheapest filter:
| Technology | 5-year $/eACH |
| AirFanta 3Pro | $53 |
| Aerolamp | $53 |
| Box fan + MERV-13 | $79 |
| Corsi-Rosenthal box | $95 |
Now let's consider noise. I have an AirFanta 3Pro, and it absolutely works. On high, it clears cooking smoke from my kitchen very quickly. But, like all commercial air purifiers that clean significant amounts of air, when you put it on high it's very noisy. As in, "hard to have a conversation in the same room" noisy. Binder describes this as "audible fans", but that's a huge understatement when you're talking about running them on high. When filters are too noisy, people unplug them. Here's one I saw this weekend, just before I took the initiative to plug it back in:
So lets say we we model running these filters at half speed, which cuts filtration by about half and noise by a lot more:
| Technology | 5-year $/eACH |
| AirFanta 3Pro | $106 |
| Aerolamp | $53 |
| Box fan + MERV-13 | $158 |
| Corsi-Rosenthal box | $190 |
Now the filters are significantly more expensive per ACH than the Aerolamp. And they're still moderately noisy while far-UVC is silent.
The advantage grows for larger rooms. Consider one that's 20m by 12m, with the same 2.5m ceiling. This room has 8x the volume, and how much air you need to clean to "change out" the whole room is proportional to volume, so an eACH now represents 8x more cleaning. Modeling filters is simple, since they clean air at a constant rate, so their $/eACH values are now 8x higher. For UVC, however, the lamp cleans more air because it's light: it can go further in a larger room. Modeling with Illuminate and pointing the lamp from a ceiling corner to a spot in the middle of the floor I get a median eACH of 2.2 (1.9 with degradation), compared to the 1.4 you'd expect if it was linear with volume. Here's the same table for this 8x bigger room:
| Technology | 5-year $/eACH |
| AirFanta 3Pro | $848 |
| Aerolamp | $230 |
| Box fan + MERV-13 | $1,264 |
| Corsi-Rosenthal box | $1,520 |
Getting to somewhat uncommon room shapes, if the room is also taller, say 6m (20ft), as large gathering places can be, we've added another factor of 2.4 to the room's volume. The filter costs go up by 2.4x, but modeling with Illuminate I get a median eACH of 1.6 (1.4 with degradation). Costs are now:
| Technology | 5-year $/eACH |
| AirFanta 3Pro | $2,035 |
| Aerolamp | $316 |
| Box fan + MERV-13 | $3,033 |
| Corsi-Rosenthal box | $3,648 |
In this large room, for a given level of filtration the Aerolamp is 1/6th the cost of the next cheapest option. Far-UVC really shines here. This is why I've advocated for it in dance halls, and why the dance I helped organize until very recently decided to deploy far-UVC:
youtube; see the stand with four lights on stage
In the other direction, while Binder is right that fans are commodity items, fans that move large volumes of air extremely quietly are not. No one makes a commercial air purifier that approaches the limits of what's possible if you design for maximum air cleaning at minimum noise. So while the best far-UVC options outperform the best filter options in medium to large rooms today, future improvements in air purifier design might change that.
Despite the critical tone, I'm very happy Binder shared this, and there's a lot of good thinking in the piece. The point that filters are useful for a lot more scenarios, including pollen and smoke (I couldn't replace my kitchen AirFanta with an Aerolamp!) is an important one, especially as we push for everyday clean air. But I do hope he'll reconsider the potential for far-UVC to produce much more clean air for a given budget in dollars and noise.
[1] After drafting this I asked Opus 4.7 "What are the errors Jeff
Kaufman would point out on
https://defensesindepth.bio/on-far-uvc-and-air-filtration-2/ ?" It
found (1) and (2) but not (3).
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Fiction
Apr. 27th, 2026 02:44 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
rivkatT. Kingfisher, Illuminations: ( fun for younger readers )
Dessa, Tits on the Moon: ( poetry )
Cat Sebastian, Star Shipped: ( romance on set )
Nnedi Okorafor, Death of the Author: ( racialized posthumanism )
Kai Butler, Shadow Throne King: ( assassin's need )
T. Kingfisher, Snake-Eater: ( western approaches )
Laura Elliott, Awakened: ( grumpy review of apocalypse premise )
Tasha Suri, The Isle in the Silver Sea: ( excellent fantasy about stories )
Jim Butcher, Twelve Months: ( the saga continues )
Ilona Andrews, This Kingdom Will Not Kill Me: ( isekai done just right for me )
sidecar
Apr. 24th, 2026 05:56 pmsmittenkitchen_feed
Contra Events Pairing Callers By Age?
Apr. 24th, 2026 08:00 amjkaufman_feedA friend observed a pattern where contra dance events seem to be pairing older and younger callers. I looked over my notes for two-caller events in 2025 and saw [1]:
- Two older callers: 33 events
- One of each: 30 events
- Two younger callers: 4 events
Seems pretty clear evidence of pairing, no? But this actually turns out to be what you'd expect to see if organizers ignored age.
With 67 two-caller events there are 134 slots. Of these, 96 (72%) went to older callers and 38 (28%) went to younger ones. So there are four possibilities:
| caller 1 older | caller 1 younger | |
|---|---|---|
| caller 2 older | 72% * 72% | 28% * 72% |
| caller 2 younger | 72% * 28% | 28% * 28% |
This gives us:
- Two older callers: 34 events (72% * 72%), vs 33 observed
- One of each: 27 events (72% * 28% + 28% * 72%), vs 30 observed
- Two younger callers: 5 events (28% * 28%), vs 4 observed
While this is very slightly in the direction you'd expect if organizers preferred to match different-age callers, it's well within what you could get by chance. It looks to me like this is just "two moderately rare events both happening is very rare."
We can compare this to the situation with gender, where you consistently get male-female pairs more often than you'd expect by chance:
The biggest caveat, though, is that this is based on a count of just one year's bookings. If I had more time, I'd like to go back over all the past data and count, but I really don't.
[1] Age is continuous, so this bucketing is somewhat arbitrary. Since
most callers are either baby boomers or millennials, though, I do think
there are two meaningful groups. I also don't know how old almost
anyone actually is, so am just guessing from appearance.
Your Supplies Probably Won't Be Stolen in a Disaster
Apr. 22nd, 2026 08:00 amjkaufman_feedWhen I write about things like storing food or medication in case of disaster, one common response I get is that it doesn't matter: society will break down, and people who are stronger than you will take your stuff. This seemed plausible at first, but it's actually way off.
Looking at past disasters, people mostly fall somewhere on a "kind and supportive" to "keep to themselves" spectrum. When there is looting it's typically directed at stores, not homes, and violence is mostly in the streets. Having supplies at home lets you stay out of the way.
One distinction it's worth making is between short (hurricane, earthquake) and long (siege, economic collapse, famine) disasters. Having what you need at home is really helpful in both cases, but differently so.
In short disasters (1917 Halifax explosion, London Blitz, 1985 Mexico City earthquake, 2011 Japanese earthquake and tsunami) you typically see sharing and mutual aid. Stored supplies mean you're not competing for scarce resources, have slack to help others, and make you more comfortable.
Stories of looting in situations like this are often exaggerated or cherry-picked. I had heard post-Katrina New Orleans had a lot of looting, but this was actually rumor. There's a really good article, "Katrina Takes a Toll on Truth, News Accuracy" on how rumors got reported as fact, and how the truth was nowhere near this bad. But the rumors had real effect at the time, including contributing to police and vigilante overreaction. Future disasters will also have rumors and reckless people with guns trying to be the 'good guys'; more reason to stock what you need so you can stay home.
Long disasters are uglier. Here I think having supplies matters even more, but so does caution. The siege of Leningrad is a pretty extreme example, where survival mostly came down to things outside people's control (ex: ration categories). When people did have stored food, however, it was very helpful as long as they were discreet. As people became increasingly desperate over the prolonged siege-induced starvation there are stories of people cooking at night or eating food raw to avoid alerting their neighbors (and, in the case of raw food, also because of lack of fuel).
Argentina and Venezuela are less extreme examples, but still informative. Because these were not nearly as severe as Leningrad there was much less societal breakdown. When there was violence and theft, it was concentrated around stores and transit; while there were home robberies this was uncommon. People who had more at home needed to shop less, which meant less exposure.
Similarly, in the siege of Sarajevo the risk was different (snipers and shelling, not robbers) but the takeaway is the same: people who had supplies and were able to stay home were less exposed to the risk.
Across both short and long disasters the pattern is similar: risk is mostly external, homes are rarely targeted, and having supplies that let you stay home is protective. The "people who are stronger than you will take your stuff" still happens, and in long disasters it's worth putting thought into how to avoid being a visible target, but it's not a major factor and it's not nearly enough to outweigh the value of having food and other resources on hand.
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Automated Deanonymization is Here
Apr. 21st, 2026 08:00 amjkaufman_feedThree years ago I wrote about how we should be preparing for less privacy: technology will make previously-private things public. I applied this by showing how I could deanonymize people on the EA Forum. In 2023 this looked like writing custom code to use stylometry on an exported corpus representing a small group of people; today it looks like prompting "I have a fun puzzle for you: can you guess who wrote the following?"
Kelsey Piper writes about how Opus 4.7 could identify her writing from short snippets, and I decided to give it a try. Here's a paragraph from an unpublished blog post:
Tonight she was thinking more about how unfair milking is to cows, primarily the part where their calves are taken away, and decided she would stop eating dairy as well. This is tricky, since she's a picky eater and almost everything she likes has some amount of dairy. I told her it was ok if she gave up dairy, as long as she replaced it nutritionally. The main tricky thing here is the protein (lysine). We talked through some options (beans, nuts, tofu, meat substitutes, etc) and she didn't want to eat any of them except breaded and deep-fried tofu (which is tasty, but also not somethign I can make all the time). We decided to go to the grocery store.
Correctly identified as me. Perhaps a shorter one?
My extended family on my mom's side recently got together for a week, which was mostly really nice. Someone was asking me how our family handles this: who goes, what do we do, how do we schedule it, how much does it cost, where do we stay, etc, and I thought I'd write something up.
Also correctly identified as me, with "Julia Wise" as a second guess.
And an email to the BIDA Board:
I spent a bit thinking through these, and while I think something like this might work, I also realized I don't know why we currently run the fans the direction we do. Could they blow in from the parking lot, and out to the back? This would give more time for the air to warm up and disperse before flowing past the dancers. We'd need to make sure to keep the stage door closed to not freeze the musicians.
Also correctly identified as me.
While in Kelsey's testing this appeared to be an ability specific to Opus 4.7, when I gave these three paragraphs to ChatGPT Thinking 5.4 and Gemini 3.1 Pro, however, they also got all three.
On the other hand, when I gave the same models four of my college application drafts from 2003 (332, 418, 541, and 602 words) they didn't identify me in any of them, so my style seems to have drifted more than Kelsey's over time.
Now, like Kelsey, being prolific means the models have a lot to go on. But models are rapidly improving everywhere, so even if the best models fail your testing today, don't count yourself safe.
The most future-proof option is just not to write anonymously, but there are good reasons for anonymity. I recommend a prompt like "Could you rephrase the following in the style of Kelsey Piper?" Not only is Kelsey a great writer, but if we all do this she'll have excellent plausible deniability for her own anonymous writing.
MixedHTML Mode for Emacs
Apr. 19th, 2026 08:00 amjkaufman_feedI made a new major mode for emacs: mixed-html-mode. Or, really, Claude Code made one at my direction. It does syntax highlighting in HTML files with inline CSS and JS. I had two goals, which weren't met by any mode I could find:
Does not freeze, flash, or stutter, even on huge files on slow machines.
Does not get confused about whether a portion of a file is HTML vs CSS vs JS.
The initial insight was that how browsers decide what text is HTML vs
CSS vs JS is super simple: scanning for literal
<script> and <style> tags. I
pulled some tricky examples, described what I wanted, and then
iterated for about an hour until I had something that worked well.
Then I tried to use it to write something for real, ran into a few
other irritations, had Claude fix those, and now I have something I'm
enjoying a lot.
It's mildly faster than web-mode (and much simpler, and easier to install), and far faster than html-ts-mode. And unlike mhtml-mode it doesn't get confused by quotes.
The biggest drawback is that it doesn't do indentation; I may add that, but right now I'm happy with it the way it is.
I've skimmed the code, but haven't read it in detail, and definitely wouldn't say I understand it. The validation has been a mixture of asking Claude to review it and fix the bugs and warts it finds, making sure Claude has written tests, and using it enough to feel good about it. I do expect it has some bugs left: if you decide to use it and find a situation it handles poorly please let me know.
It's funny: I picked emacs two decades ago because I liked the idea of an editor that was so extensible that it was mostly written in its own extension language, and then never took advantage of this because it was too much work. But now it's not much work! Perhaps emacs will finally catch up to (and overtake) vim?
Fifteen Years Aboard
Apr. 18th, 2026 08:00 amjkaufman_feedI was so excited about the first BIDA dance that I arrived two weeks early. I biked over from Medford to the Park Av Church in Arlington and was really disappointed to find the hall was empty. But I came back when the dance was actually happening, and it was fantastic.
It immediately became my favorite dance. I started volunteering, first out of frugality (volunteers get in free!) and then out of a sense of wanting to contribute, and in 2010 I joined the board. Over the past 16 years I've done just about everything at some point except treasurer, and now I'm stepping away.
It's not that I think BIDA is doing something wrong; quite the opposite! We're seeing record attendance, finances are good, so many fun dancers, and many people who want to pitch in. I noticed I would have been the seventh person running for three board spots, and realized it was a good time to let someone else have a turn. I'm excited to see what Emma, Harris, Bret, Veer, Casey, Naomi, Clara, and Persis do!
This seems like a good time to look back over how BIDA and the Boston dance community have changed over my time organizing.
The biggest change is that BIDA is now Boston's main contra dance. This is kind of hard for me to believe, since we spent so many years as a small dance that tried to fill niches that were not well covered by the many other area dances. We've gone from essentially not booking established bands to booking them regularly, and with our attendance-based bonuses are one of the best-paying dances in the country. I do really enjoy the higher level of musicianship now, but am also really glad Boston Open Contras exists (along with BIDA's open bands and family dance bands) to provide a lower-stakes environment.
The next largest change is probably the switch to gender-free calling (more history), and the level of role freedom that has come along with that. In 2010, I (and many others) would happily dance both roles, but if I was dancing the 'lady' role I had to be 100% on it because if anything went wrong it was my fault. Beginners were strongly discouraged from dancing 'switch', which also discouraged same-gender couples. And while this never happened to me in Boston, conservative men elsewhere would occasionally refuse any sort of physical contact if I encountered them in line while dancing 'lady'. When I look at the dancers now, it's amazing how people have really taken up this freedom to dance any role with any partner, which I feel really good about.
Some smaller changes:
-
BIDA went from 1x/month to 3x/month, most recently by adding a monthly afternoon dance. Since we take the hottest part of summer off, this means going from ~10 to ~28 dances annually.
We now have a dance weekend, Beantown Stomp. I kicked this off in May 2018, we had our first one in March 2019 and it's now an established and anticipated event that people fly to from across the country. I'm especially grateful for Naomi for taking the lead for 2023 (and beyond!) when I was too burnt out on organizing cancelled events (2020, 2021).
We have occasional family dances and livetronica (Spark in the Dark) events.
Our events are still intergenerational, but differently so. In 2010 most dancers were baby boomers; while BIDA was unusual in how many millennials we had, we were still 50%+ baby boomers. At this point I'd guess our dances are fewer than 10% baby boomers: many have aged out of dancing, and many millennial-and-younger dancers have joined. This is also reflected in the board's focus: the initial board was primarily mid-20s people thinking about how to get more 15-35yos dancing, but since we've succeeded at this it's no longer a focus.
We now schedule (and pay) hall managers. In 2010 we just expected most board members would be at most dances and this would give us enough coverage.
BIDA is a lot more organizationally mature. Minutes from the early days say things like "We agreed not to have a President. Instead, we'll use everyone in the board to make sure that we stay on top of things." This turned out not to work very well, and instead specific roles are in charge of staying on top of specific things, with the intraboard coordinator handling things by default.
We were still bouncing around between a few halls, and now we're always at the Cambridge Masonic Hall.
We're a legal entity now, incorporated as a Massachusetts non-profit.
We set up a safety policy, with a committee to handle issues as they come up.
There used to be a lot more of a mentoring focus. Early dances were often two experienced musicians plus a new musician. Callers would typically have a shadow. Every dance allowed sit-ins (off mic, behind the band). We hosted jams about as often as dances. I see this change as pretty natural, and I think a lot of this is now happening informally outside of BIDA.
Organizing BIDA has been a big part of my identity, but I think it's healthy for the organization to have people cycle through, and I'm confident it's in good hands. Very excited to start attending dances just as a dancer, with no formal responsibility!
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braised leeks and lentils with arugula and yogurt
Apr. 16th, 2026 08:48 pmsmittenkitchen_feed
