Why don't hand dryers use warm air?

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?

Because it takes energy to make air warm.

The problem is actually the thermal inertia of the dryer mechanism and the maximum current draw you would want for such an appliance.

Those Dyson driers actually work pretty well. Maybe well enough that they felt no need to heat up the air further.

I think the bigger problem is that public toilet doors are almost universally designed to open inwards, so you must grasp and turn a handle to exit. That’s why blow dryers are not an acceptable substitute for paper towels. You need a paper towel to grasp the handle to exit, otherwise you’re just transferring fecal contamination back onto your hands from the last 30 people who used the bathroom and didn’t wash their hands.

Yep, I always have a bottle of handsantizer. I do not like public facilities. I’m sort of a germaphobe. Occasionally I have to use them, but I’m prepared. Worse comes to worse I’ll wash my hands and shake my hands dry. I would never touch a door knob it a restroom. There are ways, I assure you, to get out of a door with hands-free or covered hands.

Not sure what you call lukewarm, I’ve never used one that didn’t have heated air.

After reading the OP I went across the hall to the rest room to test the hand dryer. After 30 seconds of a 1 minute cycle the hand dryer was blowing fairly warm. After it stopped I immediately punched the button again for another cycle. By that time it was blowing hot air. So hot that it wasn’t really comfortable to keep dry hands under it.

I think the heating element weakens after time and that’s why the OP’s units aren’t blowing warm. They’re not designed to blow cool air.

The Dyson ones are horrible. They spray dirty water up into your face and all around the bathroom.

Back in the 90s, the hospital where I worked moved, lock stock and barrel, into a brand new building. Two weeks earlier a team had gone round and removed all the never-used warm-air hand dryers from the toilets, dozens of them, and fitted paper towel dispensers. We were told that this was because the problems caused by blowing stuff around were worse than the problem of paper towel litter.

That has yet to happen to me :slight_smile: Stuff did not blow around the room, either. Makes you wonder if there are any controlled experiments establishing what drying method is most hygienic, though.

At any rate, the manufacturer claims that blasting the air fast enough makes your hands dry quickly even at room temperature. IME they do get dry relatively quickly, but I have not timed it.

??? 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.

When Dysons are available, I use a combination of them and a towel, which takes less time than a regular hand dryer and gets my hands dryer than either a towel or dryer alone. The towel sops up the major reservoirs of water, which the Dyson and other dryers leave behind, and the Dyson gets the rest of the hand dry (whereas towels never seem to complete the job and leave my hands feeling somewhat moist overall.)

Also, keep in mind that the act of evaporating the water off your hands will make warm air from a hand dryer feel much cooler. So even if it’s blowing fairly hot air, your hands will feel the stream of air as cool until they’re pretty much dry. Then, suddenly, the air will feel quite warm.

I’m not saying that there aren’t a lot of shitty dryers out there that don’t get hot enough, or hot at all. But for the ones that do get warm, that’s something to consider. Try holding one wet hand and one dry hand under a warm air dryer to see for yourself.

When I was in France, I noticed the air dryers were much better than in the US. Someone pointed out it was because they used 220 V current.

How warm they are varies by brand. The Xlerator is usually pretty good, but other brands are iffy.

As for spreading germs, have there been reports of an increase of cases of dysentery and cholera since they became widespread? Are diseases from fecal contamination rampant nowadays?

I know! What could be worse than a few drops of water on your fingers?

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.

The only dryers I’ve used that are worth a damn are the newer Dyson or Dyson-like
“blade” dryers that you stick your hands down into that have been in use over the last 5 years or so. They do use warm air but the main feature is high power air over a relatively short surface area that pushes the water down.

The old school types with the downward facing metal nozzle are useless, heated or not. It’s not the heat that gets water off your hands, it’s airflow and those simply don’t cut it.

The Skeptics Guide to the Universe podcast #702(December 22, 2018) tackled the question of Air Driers vs Paper Towels.

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?