# urine crystals in the hand dryers **URL:** \ **Category:** Factual Questions\ **Created:** [January 12, 2006, 6:13pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691 "2006-01-12T18:13:55Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [January 12, 2006, 6:13pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/1 "2006-01-12T18:13:55Z")
I admit, I heard this on Bob and Tom this morning. They read a viewer letter saying some warm air hand dryers in public bathrooms collect urine crystals in the filters. I smell a lot of things in public toilets, but this is the first time I think I smell bullshit. Snopes was no help…How about here? Any public toilet hand air dryer experts out there able to confirm or refute this claim. ---
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [January 12, 2006, 6:16pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/2 "2006-01-12T18:16:48Z")
“viewer letter” ha! I’m such a dope ---
**Author:** ![NurseCarmen](https://avatars.discourse-cdn.com/v4/letter/n/5daacb/32.png) [@NurseCarmen](https://boards.straightdope.com/u/NurseCarmen)\ **Post date:** [January 12, 2006, 6:28pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/3 "2006-01-12T18:28:06Z")
If it’s crystalized, what’s the harm? Are you planning on licking the heating elements? ---
**Author:** ![Dragwyr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dragwyr/32/2855_2.png) [@Dragwyr](https://boards.straightdope.com/u/Dragwyr)\ **Post date:** [January 12, 2006, 8:22pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/4 "2006-01-12T20:22:19Z")
I have heard that warm air hand dryers are to be avoided. [This link gives some good reasons why:](http://www.joes-sanitation.com/adults.html) From the section entitled, “DRYING METHODS” > [@](#): > > …avoid using hot-air-dryers, which receive uniformly bad marks from most experts for several reasons: First, most hot-air dryers pull their air not from the outside but from the bathroom floor–not exactly the most sanitary place even in a relatively clean facility. Second, most people don’t dry their hands thoroughly with the dryer, which can cause chapping, cracking and, hence, more chance of picking up an infection. It also makes the point that you don’t find warm air hand dryers in most hospitals. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [January 12, 2006, 8:30pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/5 "2006-01-12T20:30:21Z")
Do they even have filters? I’m sure my hair dryer doesn’t, and I don’t see why a hand dryer would be any different. ---
**Author:** ![Valgard](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Valgard](https://boards.straightdope.com/u/Valgard)\ **Post date:** [January 12, 2006, 8:55pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/6 "2006-01-12T20:55:25Z")
> [@Dragwyr](#): > > I have heard that warm air hand dryers are to be avoided. > > [This link gives some good reasons why:](http://www.joes-sanitation.com/adults.html) > > From the section entitled, "DRYING METHODS"It also makes the point that you don’t find warm air hand dryers in most hospitals. That sounds a little odd for a couple of reasons: 1. All the hand dryers that I have seen are mounted about 4 feet off the floor - they don’t appear to be pulling air “from the bathroom floor”. If the air that high is so bad when pumped through a hot-air dryer we’d better all be holding our breath in the first place. 2. Urine is sterile - as disgusting as it might be to get drops of it on your hands it’s unlikely to kill you. 3. Not drying your hands enough causes chapping and cracked skin? I thought that drying them TOO MUCH caused that? In any case a lot of guys seem to just wet their hands at the sink, shake them off and walk out. Frankly I’m more concerned about the knob on the sink and the door handle as sources of contamination since so few people appear to even use soap. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [January 12, 2006, 9:06pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/7 "2006-01-12T21:06:11Z")
Just the claim that those things have filters pegs my BS meter. At best, they have screens to keep fingers out. And, it’s not like they have an intake duct that goes to the floor - they pull in air from the height they’re mounted at, which is usually around four feet off the floor. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 12, 2006, 10:35pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/8 "2006-01-12T22:35:54Z")
Just how does urine, in any form, get into the dryer? If filters are collecting these (likely nonexistent) urine crystals, then why is there any concern? They’re in the filter, not in the airstream. ---
**Author:** ![MLS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MLS](https://boards.straightdope.com/u/MLS)\ **Post date:** [January 13, 2006, 1:00am UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/9 "2006-01-13T01:00:00Z")
If said urine crytals were indeed in the dryer, I’d guess they got there from (a) being sucked in from the air rising from the floor and/or (b) from the insufficiently washed and rinsed hands of the users. I’ve also heard the theory that the dryers are actually less sanitary than paper towels because at least the towels are all (theoretically) stuffed into a garbage container, but the air dryers blow the offensive and deadly germs :dubious: aroung the room. The instructions on air dryers should read (1) shake water off hands (2) push button (3) wipe hands on pants. That said, I find it hard to believe that we are in any kind of real danger from either towels or air dryers in a rest room unless it is never cleaned and is used mostly by carriers of typhus and dysentary. ---
**Author:** ![Yeah](https://avatars.discourse-cdn.com/v4/letter/y/dbc845/32.png) [@Yeah](https://boards.straightdope.com/u/Yeah)\ **Post date:** [January 13, 2006, 1:15am UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/10 "2006-01-13T01:15:03Z")
1. What in the world are “urine crystals”? Urine is mostly water, so do you mean ice? Urine also contains a small amount of a mixture of proteins and protein fragments, but nothing pure enough to cyrstalize. Both salt and urea are found in urine, but both are innocuous (one enough to eat, the other enough to spread on your lawn). 2. Has anyone EVER heard of ANY disease being transmitted in a public restroom as a result of the use of either hand dryers or paper towels? What disease? Where? When? To whom? I’m aware of lots of diseases transmitted via feces and some via urine but have never heard of either one transmitted in a public restroom (public restaurant, yes; public pool; yes; but public restroom, no). ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 13, 2006, 3:04am UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/11 "2006-01-13T03:04:03Z")
> [@MLS](#): > > If said urine crytals were indeed in the dryer, I’d guess they got there from (a) being sucked in from the air rising from the floor and/or (b) from the insufficiently washed and rinsed hands of the users. Except virtually no one pees on the floor right next to the drier, urine isn’t particularly volatile, and anything on the floor is going to get scuffed and scraped into oblivion; and if hands are wet enough to need to be dried, it’s pretty hard to imagine any traces of urine weren’t rinsed off, plus whatever’s on the hands is being blown away from the drier, not towards it. In other words, I find the contention referenced in the OP wholly implausible. It seems any idiot can make any claim, and there’s always some gullible yahoos around to uncritically buy it and spread it as if it were gospel. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [January 13, 2006, 3:44am UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/12 "2006-01-13T03:44:01Z")
> [@Valgard](#): > > Urine is sterile - as disgusting as it might be to get drops of it on your hands it’s unlikely to kill you. Urine in the bladder is sterile. Urine just passed from bladder to the confines of a public washroom is far less so. It generally gets laden with cellular debris and bacteria on its way out. If it finds its way onto the seat, the floor, the walls, and so forth, it then becomes a nice incubator for bacteria. That ammonia smell so notable in many public washrooms comes from bacteria munching on all that urea in urine. Even so, I must agree that it’s damn unlikely to kill anybody. Or even make anyone sick. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [January 13, 2006, 4:00am UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/13 "2006-01-13T04:00:35Z")
So what, I say. I don’t believe in babying my immune system. I want it to be ready to go 15 rounds with the toughest contaminants I might meet up with. Therefore, I don’t worry about it being exercised by a little dirt here and there. And anyone who was raised anywhere near a 1930’s farmyard probably agrees. 😃 ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [January 13, 2006, 4:31am UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/14 "2006-01-13T04:31:03Z")
> [@Yeah](#): > > 1. What in the world are “urine crystals”? Urine is mostly water, so do you mean ice? Of course note. Anyone who’s ever had to clean up after a puppy several hours after the fact has seen urine “crystallize.” Crystallization here means crystallized minerals left after evaporation, same as rock candy. I had a cat who had cystitis, with stuff crystallizing out of his urine and blocking his urethra. ---
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [January 13, 2006, 1:27pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/15 "2006-01-13T13:27:51Z")
> [@Gary T](#): > > I find the contention referenced in the OP wholly implausible. It seems any idiot can make any claim, and there’s always some gullible yahoos around to uncritically buy it and spread it as if it were gospel. Yep, I agree; and it looks like pretty much everyone who has replied agrees. It would be nice though to hear from someone who works with these things for a little more authoritative answer. I’m like the rest of you; it sounds totally implausible, but I recognize that I haven’t looked at or repaired several of these devices, so I’m in no position to say that it really is a load of crap. No offense, but it doesn’t look like anyone who has replied is in that position either. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [January 13, 2006, 2:15pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/16 "2006-01-13T14:15:57Z")
I reckon they’re probably talking about crystals of some kind of ammonia salt. It would not surprise me if these accumulated in the hand dryers. There isn’t anything intrinsically septic about ammonia crystals themselves. The part that concerns me is actually touching the button or nozzle, because you can fairly well assume that it’s covered in germs. ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [January 13, 2006, 2:21pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/17 "2006-01-13T14:21:06Z")
> [@CookingWithGas](#): > > Of course note. Anyone who’s ever had to clean up after a puppy several hours after the fact has seen urine “crystallize.” But technically, once the water has evaporated, it isn’t urine anymore. Urine is a solution of urea and water (and usually some salt as well). If urine is exposed to air, the water evaporates, leaving urea and salt. Eventually bacteria will break the urea down into ammonia, some of which will evaporate and some of which will form its own crystallized salt. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 13, 2006, 3:37pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/18 "2006-01-13T15:37:56Z")
> [@Sigene](#): > > Yep, I agree; and it looks like pretty much everyone who has replied agrees. It would be nice though to hear from someone who works with these things for a little more authoritative answer. > > I’m like the rest of you; it sounds totally implausible, but I recognize that I haven’t looked at or repaired several of these devices, so I’m in no position to say that it really is a load of crap. > > No offense, but it doesn’t look like anyone who has replied is in that position either. Agreed. I’m certainly not. But to go off in a philosophical direction, how many people in the entire country have personal experience with the innards of hand dryers? Are they even dissassembled? Do they even have filters? And if they do, are those filters ever analyzed for their contents? If so, how many people in the entire country have personal experience with the analysis? It’s conceivable that no one knows anything about this, aside from the 6 engineers in the world who design these things, because there’s nothing to know. So it could be essentially impossible for anyone to respond authoritatively to the question because it’s such a removed-from-reality scenario that there are no authorities on it. Which goes back to my observation of people making and spreading these claims. Naturally they never have any credible evidence, if any evidence at all. But human nature being what it is, those of us who have inquiring minds like to have a definitive answer as to whether the claims are accurate or not – and we’re the ones who end up jumping through hoops trying to prove or disprove them. So I would say, unless and until someone comes up with any actual facts in the matter, we should clearly and authoritatively say it’s not true. We probably have better qualifications (i.e., brains that work) than the fools who originate and propagate this nonsense. ---
**Author:** ![Valgard](https://avatars.discourse-cdn.com/v4/letter/v/7feea3/32.png) [@Valgard](https://boards.straightdope.com/u/Valgard)\ **Post date:** [January 13, 2006, 5:08pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/19 "2006-01-13T17:08:26Z")
[http://www.wmin.ac.uk/~redwayk/research/WADsummary98.htm](http://www.wmin.ac.uk/~redwayk/research/WADsummary98.htm) This study of hot-air hand dryers in actual use did in fact find a variety of icky stuff living in them and being blown out into the airstream. Also that the dryers don’t stay on long enough to effectively dry the hands, and that even if they DID, most people only stick their hands under the dryer for a brief period of time anyhow (8-12 seconds, dryer runs for 30 seconds, 43 seconds would be needed). Note that this study was sponsored by the “Association Of Makers Of Soft Tissue Papers”. All the other links were directly to (a) people who sell hot-air dryers or (b) people who sell paper towels. Didn’t see much on other actual studies. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [January 13, 2006, 5:18pm UTC](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691/20 "2006-01-13T17:18:26Z")
Oh, sure, wait until I get testy to find some facts. ☹ Seriously, though, that study found bacteria in the airflow. That’s no surprise, bacteria are virtually everywhere. Urine crystals in the filters is an altogether different proposition. I still authoritatively judge it false. 😛 [Next page](https://boards.straightdope.com/t/urine-crystals-in-the-hand-dryers/339691.md?page=2)