# Why don't hand dryers use warm air? **URL:** \ **Category:** Factual Questions\ **Created:** [January 2, 2019, 4:06am UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079 "2019-01-02T04:06:40Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Ashtura](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ashtura/32/2963_2.png) [@Ashtura](https://boards.straightdope.com/u/Ashtura)\ **Post date:** [January 2, 2019, 6:27pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/21 "2019-01-02T18:27:33Z")
> [@Lucas\_Jackson](#): > > ??? There is a Dyson Blade at our gym and I use it all the time. It works better than most other kinds. I’ve never had it blow water anywhere much less in my face or around the room. I love them. Same. User error or a defective unit. They’re all over the place where I live and I’ve never had that happen. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [January 2, 2019, 6:47pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/22 "2019-01-02T18:47:30Z")
That happened to me, even if I shook my hands a bit beforehand, until I dried my hands first with a towel before I put them in the Dyson. As I said before, it is quicker than using only an old-school dryer, uses less paper than using only paper towels, and gets me feeling dryer than either method alone. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [January 2, 2019, 7:02pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/23 "2019-01-02T19:02:17Z")
Never seen or felt a drop of water sprayed by a Dyson. Even so, I prefer an Xlerator, which you would think, being open, would be far more prone to throwing water about than a Dyson, yet I haven’t noticed that either. And while regular air dryers do take some time to warm up, they always do. ---
**Author:** ![Atamasama](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/atamasama/32/12961_2.png) [@Atamasama](https://boards.straightdope.com/u/Atamasama)\ **Post date:** [January 2, 2019, 8:21pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/24 "2019-01-02T20:21:55Z")
> [@snowthx](#): > > Isn’t the rate of drying more a factor of humidity than of heat? As an example, you take a shower in the middle of summer in Phoenix, and a quick toweling and you are totally dry. Take a shower in the middle of summer in Orlando and you stay moist no matter how well-off you dry yourself. Granted, the latter is more due to sweat, but the principle is the same - dry air dries you off, regardless of temperature. No? Warm dry air dries you off faster. Or put another way, water evaporates faster off a heated surface than a cool one. You don’t believe me, pour a tablespoon of water on a cold pan and a hot pan and see which one dries off faster. But yes, humidity is bad. I lived on Guam for two years and if you are wet you will stay wet. The air was pretty much always fully saturated, so it didn’t matter how warm it was. ---
**Author:** ![joema](https://avatars.discourse-cdn.com/v4/letter/j/a9adbd/32.png) [@joema](https://boards.straightdope.com/u/joema)\ **Post date:** [January 2, 2019, 9:25pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/25 "2019-01-02T21:25:59Z")
> [@Patch](#): > > I’ve noticed over the years that it’s almost a rule that a hand dryer in a restroom will use cold or lukewarm air, maybe warming up after a long time, making it difficult to dry your hands… If the dryer is working correctly it gets hot pretty quickly. If they don’t it hasn’t been maintained and is malfunctioning. Traditional hot air hand dryers pull about 20 amps AC at 115v, and about 2 amps of this is the fan motor. So 90% of the energy is for heat. It’s ironic many of those have a little placard with a green tree saying it’s better for the environment than turning trees into paper towels. Trees are a renewable resource and the electrical power consumed is largely from fossil fuels. OTOH some studies have shown that paper towels consume lots of landfill space (if not recycled). So there is an argument that using the electric power is a better tradeoff. The newer Dyson airblade dryers consume roughly 1/2 the electrical power, roughly 10-11 amps at 115v, since they expend most of that power on high velocity air, not heat. Maybe they are more durable without a heating element to require replacement. However one study showed that both types of hand dryers are more susceptible to bacteriological contamination than paper towels. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [January 2, 2019, 9:34pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/26 "2019-01-02T21:34:42Z")
It took me awhile but I have trained myself to use the Dyson without touching it as it is proximity-activated. You have to prepare for your hands to be buffeted around by the air and it can be difficult to not bump the sides. So I’m good, unless the study showed that the bacteria could be spread through the air and not just on the surface! ---
**Author:** ![Ashtura](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ashtura/32/2963_2.png) [@Ashtura](https://boards.straightdope.com/u/Ashtura)\ **Post date:** [January 2, 2019, 9:37pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/27 "2019-01-02T21:37:39Z")
> [@Exapno\_Mapcase](#): > > Never seen or felt a drop of water sprayed by a Dyson. Even so, I prefer an Xlerator, which you would think, being open, would be far more prone to throwing water about than a Dyson, yet I haven’t noticed that either. And while regular air dryers do take some time to warm up, they always do. Yes, the Xlerator works very well, as well, but only because it blows VERY hard. Hell, I can see my hand bones when that thing is blowing on me. ---
**Author:** ![Yeah](https://avatars.discourse-cdn.com/v4/letter/y/dbc845/32.png) [@Yeah](https://boards.straightdope.com/u/Yeah)\ **Post date:** [January 2, 2019, 10:39pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/28 "2019-01-02T22:39:57Z")
> [@Riemann](#): > > Wet hands that must now take hold of an exit door handle that has recently been grasped by the last 100 people to leave the bathroom is not good. But not bad either. The fact is that fecal-oral transmission is almost always from shit getting into unheated food or water, either directly in the field or via the dirty hands of a food preparer. I challenge the community to find documentation of any spread of any intestinal illness (other than norovirus) from adult to adult via public restroom air or any public restroom surface. ---
**Author:** ![Doug\_K](https://avatars.discourse-cdn.com/v4/letter/d/b5ac83/32.png) [@Doug\_K](https://boards.straightdope.com/u/Doug_K)\ **Post date:** [January 2, 2019, 10:58pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/29 "2019-01-02T22:58:43Z")
> [@Patch](#): > > I’ve noticed over the years that it’s almost a rule that a hand dryer in a restroom will use cold or lukewarm air, maybe warming up after a long time, making it difficult to dry your hands. It’s so annoying that if I see hand dryers I usually won’t even bother washing my hands as I know I won’t be getting them dry. > > Why don’t hand dryers use warm air? This reminds me of a problem I had when I was doing chemo. The chemo made me insanely sensitive to cold. At the school where I work I could turn on the hot water so it was warm by the time I finished at the urinal. At all too many stores, the sinks have no knobs, just sensors that turn the water on when you put your hands under the faucet and turn it off the nanosecond you remove them. The water was always ice cold in those - too cold for me to wash my hands. Same problem to a lesser extent in restrooms with no towels. A lot of the hand driers don’t come on unless you put your hands under them, but then I was greeted with a blast of room temperature air that hurt my hands almost as much as cold water, and wouldn’t warm up unless I could somehow keep my hands there for two or three minutes. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 2, 2019, 11:09pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/30 "2019-01-02T23:09:29Z")
> [@Yeah](#): > > But not bad either. > > The fact is that fecal-oral transmission is almost always from shit getting into unheated food or water, either directly in the field or via the dirty hands of a food preparer. I challenge the community to find documentation of any spread of any intestinal illness (other than norovirus) from adult to adult via public restroom air or any public restroom surface. Given that fecal-oral transmission does occur, and a public bathroom is where other people’s shit is likely to be on their hands, I’m going to put the burden of proof on you to demonstrate that faucets and exit door handles are _not_ likely to be contaminated with fecal matter before I start touching them after washing my hands. ---
**Author:** ![Yeah](https://avatars.discourse-cdn.com/v4/letter/y/dbc845/32.png) [@Yeah](https://boards.straightdope.com/u/Yeah)\ **Post date:** [January 2, 2019, 11:18pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/31 "2019-01-02T23:18:30Z")
I don’t care if they are contaminated. The straight dope is that there is no evidence indicating that they will make you sick. Fecal-oral transmission has been intensively studied for over a hundred years and thousands of outbreaks of contagious intestinal illness are worked up by smart epidemiologists every year. There are documented examples of transmission by all sorts of routes, but public restroom doorknobs in developed countries is not one of them. Just because there is a theoretical chance of something happening, does not mean that there is a realistic chance of it happening. ---
**Author:** ![snowthx](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snowthx/32/10660_2.png) [@snowthx](https://boards.straightdope.com/u/snowthx)\ **Post date:** [January 2, 2019, 11:33pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/32 "2019-01-02T23:33:13Z")
> [@Yeah](#): > > I don’t care if they are contaminated. The straight dope is that there is no evidence indicating that they will make you sick. > > Fecal-oral transmission has been intensively studied for over a hundred years and thousands of outbreaks of contagious intestinal illness are worked up by smart epidemiologists every year. There are documented examples of transmission by all sorts of routes, but public restroom doorknobs in developed countries is not one of them. > > Just because there is a theoretical chance of something happening, does not mean that there is a realistic chance of it happening. I get what you are saying and agree with your assessment. However, and this is just observation… two men walk into the men’s room at the same time, face the wall and do their business, zip-up, and head for the door. However, one stops at the sink to wash hands, while the other just opens the door and leaves. If I were the guy who stopped to wash, would I want to grab that door handle? While not necessarily fecal in nature, any doorknob is likely to be a vector for something bad, isn’t it? Of course, that scenario makes some assumptions: that every guy hold his junk while urinating and/or giving it a couple shakes when done, and that there is something dirty or dangerous transferred to a guy’s hand, and thus to the doorknob. Even guys who do a cursory wash don’t really clean anything anyway, do they? Why not use a paper towel to create a brief barrier while exiting the room? ---
**Author:** ![Atamasama](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/atamasama/32/12961_2.png) [@Atamasama](https://boards.straightdope.com/u/Atamasama)\ **Post date:** [January 2, 2019, 11:52pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/33 "2019-01-02T23:52:20Z")
> [@Riemann](#): > > Given that fecal-oral transmission does occur, and a public bathroom is where other people’s shit is likely to be on their hands, I’m going to put the burden of proof on you to demonstrate that faucets and exit door handles are _not_ likely to be contaminated with fecal matter before I start touching them after washing my hands. Yeah that’s right, prove a negative! Sounds reasonable. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 3, 2019, 12:04am UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/34 "2019-01-03T00:04:30Z")
If paper towels do take up a lot of space in landfills, that just makes them even better for the environment. That’s carbon sequestration. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [January 3, 2019, 12:27am UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/35 "2019-01-03T00:27:23Z")
> [@Atamasama](#): > > Yeah that’s right, prove a negative! Sounds reasonable. You’re going with “you can’t prove a negative”? That’s a foolish aphorism, it’s obviously wrong. Are you unable to prove that you are _not_ Bill Clinton? Negative claims are difficult or impossible to prove only when they are _universal_ negatives. For example, I can easily prove that there is no elephant in my living room; I can also prove that there is no elephant anywhere in my town, although it would take substantial resources to do a systematic search; but it would be almost impossible to prove definitively that there is no elephant anywhere in my state. Similarly, if I were demanding for proof that _every_ public bathroom handle were _completely_ safe that would be unreasonable. But a study of the level of contamination of a representative sample of public restrooms would be quite sufficient. The question here is whether it’s reasonable to place the _burden of proof_ on one side or the other. Is the circumstantially apparent risk of contamination great enough that it’s reasonable for me to demand direct evidence that surfaces in public restrooms are safe to touch? Ironically, Yeah’s argument (which is probably valid) rests on the fact that other commonly stated formulation of this aphorism is equally wrong. “Absence of evidence is not evidence of absence” is, in general, complete nonsense. When a hypothesis predicts that we should _expect_ to see evidence, and we see none, then of course that is evidence that the hypothesis is wrong. My hypothesis - public restroom doorhandles are contaminated - predicts that we should see documented cases of disease transmission. According to Yeah, in extensive studies we see none. Therefore, it’s reasonable to conclude that they are probably not seriously contaminated. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [January 3, 2019, 12:59am UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/36 "2019-01-03T00:59:28Z")
> [@Chronos](#): > > If paper towels do take up a lot of space in landfills, that just makes them even better for the environment. That’s carbon sequestration. That makes me wonder how paper towels compare to rolls of cloth towels. No paper to throw away, but the cloth must be laundered, which has its own environmental impact. ---
**Author:** ![Ashtura](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ashtura/32/2963_2.png) [@Ashtura](https://boards.straightdope.com/u/Ashtura)\ **Post date:** [January 3, 2019, 2:59am UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/37 "2019-01-03T02:59:16Z")
God damn people, use the bottom of your shirt for bathroom door knobs. I was yelling this at the supposed genius during the bathroom scene in _The Aviator_. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [January 3, 2019, 3:26am UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/38 "2019-01-03T03:26:33Z")
> [@snowthx](#): > > I get what you are saying and agree with your assessment. However, and this is just observation… two men walk into the men’s room at the same time, face the wall and do their business, zip-up, and head for the door. However, one stops at the sink to wash hands, while the other just opens the door and leaves. If I were the guy who stopped to wash, would I want to grab that door handle? While not necessarily fecal in nature, any doorknob is likely to be a vector for something bad, isn’t it? Yes, the handles on the shopping carts are likely more germ-laden than the restroom door handles. From my experience working with grocers, the restrooms are cleaned at least twice a day, and cleaning the door handles is always included. But the shopping carts are hardly ever cleaned routinely – only if one is visibly dirty will it get taken in back and cleaned. So the shopping cart handles are more likely to be dirty. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [January 3, 2019, 3:57am UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/39 "2019-01-03T03:57:58Z")
I once was in a restroom where the instructions embossed onto the hand dryer were as follows: 1. Shake off excess moisture from hands 2. Press ‘ON’ button 3. Place hands under vent while gently rubbing them together To which someone had added in black marker: 1. Wipe hands on pants ---
**Author:** ![MikeF](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@MikeF](https://boards.straightdope.com/u/MikeF)\ **Post date:** [January 3, 2019, 5:05pm UTC](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079/40 "2019-01-03T17:05:16Z")
> [@Yeah](#): > > I don’t care if they are contaminated. The straight dope is that there is no evidence indicating that they will make you sick. > > Fecal-oral transmission has been intensively studied for over a hundred years and thousands of outbreaks of contagious intestinal illness are worked up by smart epidemiologists every year. There are documented examples of transmission by all sorts of routes, but public restroom doorknobs in developed countries is not one of them. > > Just because there is a theoretical chance of something happening, does not mean that there is a realistic chance of it happening. With exactly zero proof or cites to support my belief, I agree. I always thought this whole bathroom thing was overblown. If it was such a big deal, people would dropping like flies. [Previous page](https://boards.straightdope.com/t/why-dont-hand-dryers-use-warm-air/827079.md?page=1)