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The bacterial horror of hot-air hand dryers (2018) (health.harvard.edu)
75 points by rascul on Oct 27, 2023 | hide | past | favorite | 81 comments



It seems like I could go to great lengths to be a germaphobe and take extraordinary precautions at every turn, or I could not do that at all and just wing it, and either way I will get between one and two mild-to-moderate head colds every year. And this is in NYC where I spend half my life in crowded spaces. Just doesn't seem worth the hassle to give a shit.


As the dad of a 6 y/o… I envy your 1-2 colds per year, it’s more like 1-3 a month for me. I WFH and never go to crowded spaces.


Yeah, I empathize with that... kids bring home everything. I think actually in your case it makes even LESS sense to worry about washing hands in public places because your kid probably gives you so many of the latest germs you are probably equipped to fight off anything you might get in public...


> I WFH and never go to crowded spaces.

Maybe you should from time to time. Your immunity cannot be trained without real world bacteria and viruses. And kindergartens are real viruses and bacteria incubators.


So you are saying 3 colds a month isn’t enough? I should modify my lifestyle with the expressed purpose of getting more? For my health?!?


Didn’t Covid tell us there is no such thing as training our immune system?


No... It didn't. It told us things arent black and white but everyone seems to have just picked a color and died on that hill instead of considering that there might actually be nuance.


Are you sure? I recall that there was lots of debate on the topic of „training“ an immune system. And the conclusion was that such a thing does not (scientifically observed) exist. If it does, I‘d actually be interested in the biology behind it.


I have 3 kids 6 and under :'-'(' <- that is liquid leaking from all my face holes.


Are you wearing N95s everywhere or just focussing on hand hygiene?

I thought COVID busted the whole “wash your hands to avoid the flu” thing for viral respiratory diseases.


No, covid does not often spread that way but a large number of other common viruses do.


Which viral respiratory ones?

I thought most of them (influenza, parainfluenza, RSV and all the other coronaviruses) were enveloped viruses like covid-19.

I guess adenoviruses would be the exception.


Look up “fomite transmission.” Rhinovirus colds do transmit that way. Most are also transmitted by aerosols, so you are correct in that… people were wrong that thought you could virtually eliminate virus transmission by just washing your hands a lot.


for example, https://en.m.wikipedia.org/wiki/Norovirus

alcohol can not kill everything.


Yea, because norovirus is a non-enveloped virus, unlike coronaviruses, influenza, parainfluenza and rhinoviruses.

Also it’s what contributes to norovirus being primarily a GI virus (it gets past extreme pH of the stomach).


These hot germ rockets are bad enough on their own, and then they also deprive you of a nice clean paper towel to open the bathroom door with on your way out. Barbarous!


I have been known to pull my Leatherman out of my pocket and use that to touch the door handle if possible. I'll do just about anything to not have to touch the door handle.


Bidirectionally pushable doors for the win! You can just push with your foot.


Even better, the serpentine entrances to washrooms that don't even require a door


You can also pull with your foot. It's something you learn if you really don't want to touch those door handles.


> The vast majority of the microbes that were detected do not cause disease in healthy people, with the exception of Staphylococcus aureus. Some of the bathroom bacteria, such as Acinetobacter, only cause infections in people in the hospital, or in those with weak immune systems. The others that were found are relatively harmless.

> In addition, air from real-world bathrooms may contain fewer bacteria than the bathrooms in the study. The sampled restrooms were located in a university health sciences building, and at least some of the bacteria came from experiments going on in laboratories within the building.


On the topic of unfortunate mingling with research, for an AIDS drug, ritonavir, it can come in multiple crystalline forms.

But this was unknown.

For years manufacturers only knew about and produced “Form 1” without issue for years until “Form 2” showed up out of nowhere. Maybe from a lab studying it, who knows.

But once it’s out, as it’s more stable, it’s preferred! It “infected” a key manufacturing plant with it, and the batches kept showing up in that form. And cleaning it away is virtually impossible.

> And Form Two went everywhere. Within days of identifying Form Two, the company’s analytical lab could only make that form of the drug. The bulk drug coming off the production line in Chicago turned out to be contaminated before it ever went in to the capsules. Staff from Chicago were sent to an uncontaminated production line in Italy to find out if they were doing anything differently. Within weeks, that line was producing Form Two as well.

As it’s more stable, it means it doesn’t dissolve as well, but is also favoured.

That’s bad news if you want a pill that dissolves in your stomach (or in this case, in the liquid capsules), or need an injectable solution.

https://www.chemistryworld.com/podcasts/ritonavir/4011593.ar...

The (fear-mongering chaser?):

> This wasn’t the first drug to show unexpected polymorphism. And it certainly wouldn’t be the last. Research published in 2018 suggests that a more stable polymorph is waiting to be created for about fifteen to fifty percent of all drugs.


My skepticism has turned to wonder.

here are the technical details: https://cmbe.engr.uga.edu/bche4520/Other/Ch9/Bauer%202001.pd...


Absolutely nuts. The fact some common drug or chemical could just change out from right underneith us one day is a weird feeling.


> do not cause disease in healthy people, with the exception of Staphylococcus aureus

I'm no biologist, but surely as with (most?) bacteria that depends on whether your immune system is regularly exposed to it or not, right?

Cursory search tells me:

> Staphylococcus aureus [...] is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. [...] Although S. aureus usually acts as a commensal of the human microbiota, it can also become an opportunistic pathogen, being a common cause of skin infections including abscesses --- https://en.wikipedia.org/wiki/Staphylococcus_aureus

> An opportunistic infection is an infection caused by pathogens [...] that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immune system --- https://en.wikipedia.org/wiki/Opportunistic_infection

Wonder how it's an exception.


S. aureus has antibiotic resistant strains (MRSA) and results in many deaths each year, particularly in hospitals

https://en.wikipedia.org/wiki/Methicillin-resistant_Staphylo...


I don't use the hot-air hand dryers because they physically hurt my ears. They're so damn loud. I don't know which one is worse, the Dyson Airblade or the Xcelerator.


I thought the same thing but someone told me that was autism so I just keep my mouth shut. lol


Someone went around measuring volume levels, and found that all were louder than 100 dBA, with the loudest being 121 dBA!

These are beyond "a tad annoying" and into "hearing damage".

https://academic.oup.com/pch/article-abstract/25/4/216/55195...


Measured at what distance?

I just measured 120 dBA blowing into the mic next to my sleeping girlfriend without her waking up.

Not to question the results, but methodology is important.


The time period matters as well. Just clicking your fingers is loud enough to give you hearing damage if sustained for 30 minutes. I would not at all be worried about hand dryers unless you sat next to one all day.


> clicking

Snapping?

Or is this a new fad I don't know about?


If I had to guess I'd say English is not their first language (like it isn't mine) and they just translated a term from their own language into English ; )


I think it’s just regional. I’m quite sure clicking is the common term around me. Wikipedia has it as “snapping (or clicking)” in the first line.


I imagine the worst ones are in rooms with mostly tile so the sound has nothing to absorb it.


Can confirm that an autistic person I know is the only person I've ever seen treat bathroom hand dryers as intrusively / unbearably loud devices.


My daughter hates them. I don't think she's autistic but she does have sensitive hearing. (Whispering between her parents doesn't often go unnoticed, frustratingly sometimes.)


My 4yo daughter is getting instant panic attacks when one of those hand dryers turns on next to her. I hope this isn't a spectrum thing, but the thought often crosses my mind.


For what it's worth, loud noises always bothered me as a kid. Even the (1000-person audience) applauding after each performance of the end-of-year talent contest in my first two years of secondary school (aged 12 and 13) was so loud I managed to get taken out of the hall because I was crying from the pain.

However, despite some people trying to call me "autistic" as a term of abuse (including a line manager!), my actual score on an (online) autism spectrum test was solidly in the "mundane and normal" category.


Curious, as someone playing in a noiseband I don't even think the loudest (broken) hand drier I ever heard even remotely resembled anything I'd describe as loud. Everything is relative. I always found the dyson ones to be quiter than those old big rusty things that vibrate the whole wall as their fan spins up.

But as a sound engineer I am aware that A) there is such a thing as too loud and B) people are very subjective in what they perceive as unpleasent sounds and when it is unpleasant to them they are more sensitive to it


To me it is both the sound of the machine running and the sound of the fast moving air running over the hands. When there are multiple people drying their hands all at once, in a tile covered bathroom, I find the sound to be unbearable. Even if it's just me drying my hands, the discomfort is too much.

I have tinnitus and so my sensitivity might be lower than the average person. Other sounds that cause me pain and distress:

1. Movie theaters these days. Why are they so goddamn loud? I can't tell if it's the sound design of the movie, or if the volume is way up in the theater. If I don't wear earplugs, my ears will be in pain and ringing for days.

2. My refrigerator that has developed an obnoxious electric whine. I can hear it from across the house. It is currently being replaced, and I am spending an absurd amount of money on a quiet refrigerator.

3. A commercial carpet cleaning vacuum running for hours at a time down the block. Again with the high-pitched sound and I can hear it from a mile away. And it's always in the mornings when I am trying to read.

4. Ceramic dishware clashing together. This too causes pain. When I do the dishes, I am mindful of the loud sounds made when stacking plates and bowls, so I stack carefully. When family does the dishes, they create a soundscape from hell. It is like their hands are not connected to their brains and they've never put anything down gently in their entire lives.

5. Industrial electrical boxes. I parked on a top floor of a local parking garage the other day, and I noticed 4-6 very large electrical boxes mounted along one of the walls. The sound coming from these boxes was so loud, so sharp to my ears, I had to get back in the car right away and drive out. It only took a few moments of exposure and my ears were ringing and my head was splitting for hours.

I know I must seem insane, but I don't care. I will go out of my way to create quiet spaces, to preserve the silence, to avoid noise that causes distress, because sometimes it takes days for me to recover. And having to battle this stuff constantly just makes me angry and annoyed, and I don't like that.

I've had numerous ear and hearing exams and in addition to the tinnitus, I'm told I have severe "hyperacusis."


Thanks for the insight. I wonder how much of it is the brain. Normally the acoustic processing inside our heads is capable of reducing unfocused sounds by around 12 dB (a phenomenon described with the term "Cocktail Party Effect"). So I wonder what happens when the hearing focuses on the ubwanted stuff instead.

As for cinemas: Unless you go to weird off the beat venues the listening levels should be those specified by the mixing engineer in the studio. Most cinemas have dolby certifications, which means the engineer in the studio will hear nearly exactly what you hear.

The levels within cinema productions are painstakingly kept below any levels considered harmful by both the industry and the law for obvious reasons. That however doesn't mean it will be equally pleasant to all people or that there are some people with special hearing conditions where it might come across as downright hostile (like you).

If this happens often to you I'd suggest investing into decent hearing protection. I have one with me at all times, despite being relatively insensitive to sounds and levels that would put other people at the edge of their seats.


Respectfully, what is curious then? You are clearly aware you regularly and voluntarily engage is listening to volumes louder than average person, so it shouldn't be surprising or curious other people's threshold is lower? :)

I find air drivers uncomfortably loud. My children are terrified of them and I cannot blame them. It's the volume but also the nature of the sound that are both rather awful.


The curious thing to me was that it never occured to me air drivers are perceived as unpleasantly loud.

Don't get me wrong here, I wouldn't want to spend my day next to one of those things. But it isn't as loud as "I am afraid for my hearing"-loud.


Fair enough! Yeah, they are kind of the loudest normal thing I experience; but beyond the sheer volume, it's the nature of the sound. I may be able to listen to music potentially as loud as that drier (though I wouldn't normally:), but it's also the startup type and the shrill, offensive, high pitched noise that I think bothers people :)


It’s probably autism and it can often be the particular sound rather than just the volume. I’ve seen people who found the noise of a dishwasher for example to be very upsetting even though it’s not loud.


Much ado about nothing?

If there are so many bacteria already milling about in the air, you'd have already breathed in billions (?) of them before you got to the dryer.

If you are not immunocompromised, you do yourself a disservice by being so worried about bacteria. I don't bother with attempting to avoid or prevent that might merely inconvenience you for a while but is eminently treatable at home (flu, for example).


If the germs are from the same air that you're breathing and moving around in, and not growing inside the dryer or particularly concentrated in any way, I don't see what the problem is. The same germs will be found on the surface of paper towels or any other object in the bathroom.

The article mentions attaching HEPA filters to hand dryers, but that sounds like a terrible idea since bathrooms are often humid. A wet filter quickly becomes a breeding ground for mold.

If you really want to turn your hand dryer into an air sanitizer, how about ensuring that at some point during the air's passage through the machine, it reaches a temperature high enough to kill germs? (Cool it down a bit before it reaches the exhaust, of course.) Or maybe install a UVC lamp inside? These tricks will require a larger and much more expensive machine, though.


I find them useless simply because it takes way too long to dry the hands completely. A handkerchief or a tissue does the job in a second. Also, maybe it's just me, but I find my palms a bit sticky after drying them with hot air.


I know this sounds gross, and people will have a knee-jerk negative reaction to it, but washing your hands at all in many public bathrooms is pretty nasty. I guarantee my <encrypted> is far, far, far cleaner than anything I'd touch in a public restroom. If there's a sink faucet that needs to be manually turned on and off, that's going to be infested with bacteria. If it's a no-touch faucet, then there's no downside to washing (so long as you don't touch the rest of the sink), but I've always felt that all those air-blasting dryers were just blasting bacteria all over the place.

I always wash my hands, because societal norms strongly discourage any alternative. But I have no illusions about the fact that I'm picking up more bacteria half the time. If there are no paper towels to dry, I'll almost always just shake the water off and dry my hands on my pants instead. Beyond the bacteria-blasting, I find that hot air dryers take way too long and still leave my hands damp anyway.

And if you touch the door handle on your way out, you've thoroughly undone any cleaning you may have just performed.

Thankfully I'm not a germophobe, so I follow societal norms and wash lest I'm called out on it, and don't actively think about any of this.


I don’t have any education or training in these things so take whatever I’m saying with a huge grain of salt but I thought the point of washing hands was not to get rid of bacteria themselves but the oils naturally occurring in our hands so that bacteria has a harder time sticking to the skin on our hands?


Also not a pro, but I’m pretty sure the point is for the soap to rupture/destroy bacteria and viruses.

See: https://medicine.yale.edu/news-article/why-soap-works/


“Fecal cloud” made the article worth the read. New vocabulary.


If I ever build my own house, the plan (if code allows) is to not have a bathroom fan, and instead run the intake for an air exchanger into the bathroom. If I remodel this one I may well try to do the same. I think there's a reasonably good spot for it.

Bathrooms, particularly public ones, are wet, mouldering places with insufficient ventilation. And we go into them every day to get ourselves clean. Taking air out of the bathroom and injecting it somewhere else is about the best way I can think of to fix that, and we only run them intermittently.


No hate, and good on you for thinking about it deeply, but this is a terrible idea. The primary thing you want to exhaust from bathrooms is humidity. You want the shortest, straightest path out of the house for that 100% humid air. Recirculating it will create untold horrors of mold all the way downstream of the bathroom. It’s also unlikely to be allowed by residential building codes, or passed by any inspector.


That’s not how heat exchangers work.


I’m not sure you’re replying to the right comment. I didn’t mention heat exchangers, only air movement, replying to you talking about “air exchange.”


Wait you want to redistribute shit air to the rest of the house? Im not understanding this proposal


They said "If I ever build my own house" - I think the idea is to prevent it from becoming "shit air" in the first place by having the air exchange there from the beginning.


I think they meant “shit air” literally. As in, it doesn’t just smell like farts, it is actual farts, being proposed to be blown throughout the rest of the house


Maybe install the ERV/HRV return vent into his bathroom wall?

https://www.aprilaire.com/whole-house-products/ventilation/m...


That’s exactly what I’m taking about. Downvoters seem to not know these have existed for thirty years.


What is wrong with everyone today (yesterday)?

Does nobody hear know what an air/heat exchanger does? They’re for ventilating modern sealed construction so you don’t choke to death on fumes from your belongings, or get cancer from your wood shop.


I think the implication is he wants to run industrial air-changers 24/7, basically turning his bathroom into a fume-hood, and then venting it outside.

So, same idea as bathroom fan but really big and running it less intermittently. He wants a big industrial air-changer so his bathroom is less dank.

One problem is this will definitely suck a lot of heat out of the house. You might want to only run it when a sensor detects humidity, and just give it a ton of hysterisis/etc so that it runs a relatively long time. Pulling a bunch of heat out of your house 24/7 will be expensive and will cause other problems (like extreme low humidity since the furnace is running much more, which will lead to crazy amounts of static etc). You can of course run a humidifier (or whole-house humidifier) etc but it's generally not without problems to just dump air 24/7.

(I had similar sentiments around my current house not having good air handling for the stove, if you are frying something it can get pretty greasy/nasty inside even with the fan on, and you can't always open a window depending on the weather.)

On the other hand, this also might help with CO2/oxygen levels, which might lead to better overall health/comfort too, because your air is being cycled more aggressively. The overall thrust that houses are getting too airtight nowadays is generally correct, and this has negative health effects too. It is, again, unfortunately balanced against heating costs (energy efficiency seals the house up, then we circulate the air out...) and other problems. If the house is super breezy (or has air changers aggressively changing the air) then you're also pumping out all your heat and humidity.

If you are going to have some strong air changers though, you could run a heat pump in the air changer stage too. Being able to spend 1 unit of energy to move 10 units of heat from the exhaust back to the intake would be ideal, and the air is going outside anyway so you might as well dump waste cold (or waste heat, in the summer) outside while you're doing it.

An easier step, if you have the space in your bathroom, would just be to run a dehumidifier in the bathroom. Obviously would be pointless/inefficient during a shower, but maybe you could have a switch where one pole is "bathroom fan on" and the other one is "dehumidifier on". Or get a timer switch and just run it for an hour after the shower is done.

It is also worth noting that if you get the humidity under control in general, that the house itself will act as an "anchor" and tend to resist changes from the mean. The bathroom is dank because all the building materials around it are saturated and constantly giving off water, if you can keep it at 40-50% humidity more regularly then eventually they will dry out and the system stabilizes at a less-dank humidity.


That's what an ERV is designed to handle. They're becoming code in some places

https://www.aprilaire.com/whole-house-products/ventilation/m...


My house in Minnesota had one. The building codes were such that the first winter without we had constant condensation on the windows, which ruined the finish. Installed one later that did 4 whole house air exchanges per hour. Best investment ever.


I first encountered consumer grade versions of these on This Old House. I’m not sure when, but I stopped watching it regularly probably twenty years ago, so at least fifteen?

At the time dust collection systems were still pretty exotic, so they were putting them into wood shops to make sure the dust didn’t get sucked into the rest of the house.


Isn't the solution to have a bathroom fan that vents to the ouside?


Pretty sure bathroom fans DO vent to the outside. At least in homes here in the US.


They do in modern homes:

> If you're a homeowner, be sure that your fan is properly vented directly to the home's exterior via an insulated duct. "It was common in the '70s and '80s for it to be vented into the attic space," says Bayne. "Building codes today require that the exhaust is vented outside through insulated ducting to a roof vent that goes directly to the exterior." Otherwise, you may be contributing to moisture and mold problems in your attic or wall spaces.

https://home.howstuffworks.com/bathroom-exhaust-fan.htm

Related, but I like how kitchen exhausts sometimes come out of a vent on the side of the house, so if you go out into the backyard you can walk by and smell bacon frying or whatever. (OTOH I once lived in a condo with an under-the-microwave exhaust that didn't actually vent outside, it just spat everything up onto the kitchen ceiling... a wet greasy spot accumulated up there before I realized what was going on.)


> (OTOH I once lived in a condo with an under-the-microwave exhaust that didn't actually vent outside, it just spat everything up onto the kitchen ceiling... a wet greasy spot accumulated up there before I realized what was going on.)

Isn't the primary purpose of a kitchen vent to remove smoke from the kitchen?

How on earth is moving smoke from one part of the kitchen to another part of the kitchen supposed to improve anything? Is your smoke alarm that location-sensitive? (What if there was a fire 20 feet away from the smoke alarm?) Will it be any easier to breathe?


AFAIK the only real purpose of the recirculating range hoods is to catch grease. And it sounds like GP's was missing the grease filter. (BTW, those get -really- gross pretty fast, it's worth cleaning them regularly)

You can get grease filters now with charcoal filters embedded within, and that might help a little bit with smoke.


Hey, at least they gave you that kindness. At the last place I lived, it was configured to spray everything all over the inside of the cabinet above the microwave.


Many years ago while helping fix up a friend's newly-bought house, I encountered the same thing, although fortunately it looked like it had never been used. My first thought was that it was somehow left unfinished for some reason, but apparently it's allowed, and even somewhat common.


Augh, that's horrible. I can only imagine the scene inside that cabinet...


Many just vent to the attic.


I run my bathroom fan for hours after I shower. Drywall is a sponge after all


Not painted properly, it isn’t. Moisture protection is one of the primary benefits of paint.


Unless you're using a speciality paint, latex is too porous (for vapor, not liquid water) and gypsum too large a chemical potential well.


Yeah, “properly” was doing some work in my response :) It helps to use a glossy paint, and to put that over wet-environment primer on top of wet-environment drywall.


Cool. Rhanks for the reply




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