What Is the White Powder from Ultrasonic Humidifiers and Is It Harmful?

[chemisttree]

Life finds a way

 

[russ_watters]

I did some "closing the loop" calculations based on the airflow of my air purifier and water flow of my humidifier. I'm getting:

• For the various "distilled" and "purified" waters, <11 mg/L of dissolved solids.
• For softened tapwater, ~63 mg/L of dissolved solids.

0-75 is generally considered "soft", but what is dissolved will be different and I don't know if the mass fraction is different for the dissolved calcium vs the ion exchanged sodium. This would suggest yes, because my unsoftened water is "hard" at 150-300 mg/L.

There's a lot of confounding factors to these tests of course and the results so far vary by as much as 100% across multiple tests with the same water. One of the biggest issues that I've mostly avoided but is still notable is that when it is colder outside my heat is on more, which both reduces the humidity(room-only humidifier) and cleans the air, by different amounts. The net result is much lower particulate at the same RH.

I have not yet noticed if the precipitate is dissolving back into the water, but I might not be cleaning it often enough to notice since the boiler section only holds a few mL of water.

 

[Nik_2213]

I'm sorry, if it was 'proper' distilled water, 'Analytical Grade / AR', there would be no residue per litre-- Within experimental error, of course, of course. And there'd still be no residue from a tonne / IBC of the stuff...

One of my less-fun experiences was discovering that the bulk AR Methanol (MeOH) for our lab had again been supplied in drums with the wrong 'lacquer' coating. This had promptly dissolved and was gumming up our equipment. I modified our biggest rotary evaporator to take a fill-line via vent-tap's side-arm, force-distilled litre after litre after litre of Methanol at 'water vacuum' pressure on simmering water bath. My anti-bumping granules stuck to the accumulating gunge, but a spoonful of glass beads just kept rolling along...

 

[russ_watters]

I'm sorry, if it was 'proper' distilled water, 'Analytical Grade / AR', there would be no residue per litre-- Within experimental error, of course, of course. And there'd still be no residue from a tonne / IBC of the stuff...

Of course. But the results are way above my ability to measure zero, so the readings at least are unequivocal at that. And the possibility of contamination by me seems small - the readings are orders of magnitude above what residual water or dissolving the scale on the humidifier should cause. So I think the likely conclusion is that the water isn't well purified and/or is somewhat mixed at the factory. Here's two samples (the temperature scale tells you the central heat never turned on). In the first it ran out of water partway through the night, and there was a noticeable spike in particulate as that happened.

 

[BillTre]

This all sounds good.

The conclusion would seem to be that your residential water supply (presuming that's your source) is not great for some reason. This leaves you with three alternatives:

1. just put up with it
2. get your own equipment and make better water
3. buy better water

----------------------------
Deciding among these requires figuring out how much good water you would need, in order to figure out the costs.
So it would be gallons of water to evaporate to raise the humidity (from x to y) in the air volume of the house (at the temperature), plus considering the turnover rate, and maybe some other stuff.
Or maybe how much water does you humidifier use when you are happy with the results.
I would personally be interested in the results if you figure them out.

Once you have an idea how much water you need you can consider prices.

----------------------------
Advanced fish hobbyists in your area would be knowledgeable about your local water chemistry and how it might be treated or where it could be bought in gallon volumes.

In labs I've been in, water came in increasing quality via:
tap (from pipes)
deionized/distilled (with or without pipes)
fancy lab equipment produced ultra-pure water.

I never heard of a lab using water softener ion-exchange purifiers.

For the home, RO systems can be bought (purity, volume, and price vary).
Some RO units also have deionizer columns.

I guess you could also just get a deionizer column and use that.
I am also guessing that these operate similarly to these water purifying devices you can put on a faucet or pour through to fill a container.

 

[russ_watters]

The conclusion would seem to be that your residential water supply (presuming that's your source) is not great for some reason.

It's just a little harder than average, but yeah.

This leaves you with three alternatives:

1. just put up with it
2. get your own equipment and make better water
3. buy better water

----------------------------
Deciding among these requires figuring out how much good water you would need, in order to figure out the costs.

Yeah, I haven't decided yet how much I care, but the numbers are:

• I use probably half a gallon of water per night. This varies based on the weather of course.
• Assuming I use it every night for 4 months (I won't), that's 60 gallons for the season.
• The cheapest store-bought water I'm buying is $1.05 / gal, so that's $63 for the season.

The cost isn't awful, but buying 3 gal of water weekly is a bit of a pain.

I guess you could also just get a deionizer column and use that.
I am also guessing that these operate similarly to these water purifying devices you can put on a faucet or pour through to fill a container.

Now that's interesting, I hadn't considered that they could be bought/used separate from an RO system. An RO system starts at about $200 and most are meant for whole-house use. I'm just not there yet. Looking around though, I see point-of-use/in-line (hose connected) DI filters, which are advertised for washing cars without leaving spots. They start at about $25.

 

[Averagesupernova]

I used to have one and the cleaning of the caked-on minerals was not fun. Might as well get a chisel out.

Shouldn't vinegar take care of that? Supposed to clean up coffee makers. Not a huge coffee guy so maybe there's something better for that that I am unaware of. I'm not the guy in the household responsible for the most coffee consumption, therefore I'm not the coffee maker cleaner.

 

[Arne Andersen]

TL;DR Summary: What is the white powder a humidifier emits and is it harmful to breathe?

Ultrasonic humidifiers atomize water and inject it into the air, where it evaporates. Anything dissolved in the water precipitates out as a white powder, which is noticeable as dust on surfaces throughout the room, especially near the humidifier. If the output is high enough, it can even form a visible white cloud throughout the room. Obviously that means we breathe it. So the question is, what is it and is it harmful?

For additional context, I bought a PM2.5 detector (2.5 μm and larger particles) after the wildfires last summer. The results are interesting. (Maybe later we can discuss the hazards of gas cooking and microwave popcorn...). Among the results are poor air quality readings in my bedroom with my combination ultrasonic/evaporative humidifier on. This morning in a test it read 160 μg/m³, which is "unhealthy" According to the WHO. It reads in single digit precision and can read as low as 0-1 if the HVAC has been running a while or I'm using my air purifier. Now, of course not all particles are created equal, and this scale was invented to measure particulate air pollution, which is mainly a nasty carbon soot cocktail. But what about what this humidifier is putting out?

I've done some "research" and the results are thin. Sources mainly just say it's the same stuff as in drinking water, so that means it's fine. Be we all know that drinking and breathing it aren't the same. And it may not even be the same chemical in each case. Note, the EPA says research has not found a risk, but a medical case report claims injury to an infant due to sustained exposure.

My tap-water source is very hard (primarily calcium and magnesium), but I use a softener. I don't have any bags of the salt it uses, but google tells me it's sodium chloride - table salt. The softener uses an ion exchange process that removes calcium and magnesium and leaves the sodium. Does the sodium stay dissolved? Pure sodium metal explosively reacts with water to form sodium hydroxide (NaOH). Does this happen just after the ion exchange? These questions are why I put this in the chemistry forum.

An SDS I found for sodium hydroxide lists an inhalation hazard level of 1 mg/m³. An SDS for sodium metal mentions "metal fume fever" as an inhalation hazard, which doesn't sound good, but they don't list concentration guidelines.

Thoughts?

For now I'm running my hated air purifier when the humidifier is on.

What is formed by ion exchange is sodium chloride: Ca(HCO3)2aq + ion exchange NaCl> NaClaq +ion exchange Ca(HCO3)2

Suggests using demineralized water in humidifiers.

 

[Astronuc]

Shouldn't vinegar take care of that? Supposed to clean up coffee makers. Not a huge coffee guy so maybe there's something better for that that I am unaware of. I'm not the guy in the household responsible for the most coffee consumption, therefore I'm not the coffee maker cleaner.

We've used humidifiers before, and we had the same issue. We did use vinegar to dissolve the salts that accumulated on the surface of ultrasonic transducer window.

Some years ago, we purchased a water distiller/purifier that boils water, which is then condensed and passed through a charcoal filter. The water is mostly demineralized. There is usually some sediment (oxides presumably of Ca, Mg, Na or whatever cations happen to be in our well water - which is treated with a green sand filter and water softener). We use vinegar to dissolve the deposits, which don't amount to much; I found a combination of vinegar with drops of concentrated lemon juice (citric acid) worked very will to dissolve the deposits. We then flush with hot water.

 

[Barakn]

I've used a variety of vaporizers ranging from heaters to ultrasonic to to simple evaporation (fan blowing air through a constantly wetted filter). They've all had their issues.

I'm going to sound like a shill, but I bought a Vicks vaporizer, and it was a game-changer. My first clue that it was different was that the instructions recommended that a pinch of salt be thrown into the water. It suggested that eventually the product would break in and eventually salt would no longer need to be added, but that's not how it works for me.

Every time I dump out the older water, I add a pinch of salt, or the level of vaporization will be too low. During operation, material from the water (or air passing through) precipitates as detached little white or brown chunks which are easy to discard with the leftover water. If it runs low on water, the level of vaporization slows, and then stops, the unit doesn't overheat.

I still don't know how it works, because it just keeps on working, year after year, with little maintenance, and thus I've never had the need to disassemble it. I've pondered whether it works by electrolysis, but at 60 Hz phasing so that oxygen, hydrogen, or chlorine gas that are made are destroyed when the polarization reverses and the anode becomes the cathode, or vice versa. I don't know if this proves that I'm not a shill, but even though the vaporizer has a little tray to vaporize other Vicks products, I don't use or recommend them.

 

[russ_watters]

Aaand, we're back for another heating/humidification season.

I've bought an RO system, the cheapest I could find; $50 on Amazon plus accessories. Here it is:

It's marketed for aquariums and makes 3.6 gal/hour at my water's pressure (the bucket is 6 gal and has volume markings on the other side). I've only used the output once, but so far the results seem positive. I'll need to use it more and on colder/drier days to be sure. Meanwhile I'll be using this for other purposes such as my iron (rarely used) and coffee maker (more frequently). I expect to about break even vs buying purified water at the supermarket this year. I'm not sure how this will do after sitting for 6 months for next year, but we'll get to that later.

 

[russ_watters]

Looking around though, I see point-of-use/in-line (hose connected) DI filters, which are advertised for washing cars without leaving spots. They start at about $25.

Oh, and, yeah, that didn't work. I'm not sure what exactly it is, but it didn't help at all.

 

[BillTre]

"point-of-use/in-line (hose connected) DI filters"
"I'm not sure what exactly it is,"
it should be a resin which binds the ions out of the water.
It would have to be regenerated periodically or the resins binding sites will fill up with ions and bind no additional ones.

It would probably miss a lot of what an RO system would get: organics (by charcoal) and non-changed low molecular weight molecules (by the RO membrane).

In your system the membranes are in the center canister, one of the others is probably charcoal (AKA carbon), and the other could be a DI resin. There may be a particle filter somewhere.

In Oregon where I live, the water is very soft. I would measure it in µS of conductivity in the low 30's (that's soft). I used the RO to make especially pure water for use in raising fish. This also insulated the system from fluctuations in the quality of the water delivered by the water company (this stuff happens).
The RO system (like yours running only on line pressure) drove the conductivity down to 3-4 µS (really good for fish).
The East coast (at least Maryland where I grew up) has harder water. This would use up the replaceable parts (resins, RO membranes) of a filtration system faster. Its an ongoing expense.

In general, I would expect aquarium products to be of fairly good quality. They should work and not immediately break. The hobbyists are fairly knowledgeable about their effectiveness.
Professional systems would be bigger, use pumps to boost the water pressure used to oppose osmosis across the membranes, and be built of better materials.

 

[russ_watters]

Here's how it went for the 2024-2025 season with my new micro-RO system:

I used more than twice as much water as I projected in post #36, which means it easily paid for itself this year. The numbers:

• I tracked production/usage for 6 weeks in the core of winter: 6.4 gal/wk (does not include when I knocked over or over-flowed the bucket a few times...).
• Reject rate: 74% (this is bad, but not surprising for a small system on house pressure).
• Total usage: 146 gal (assumes 3 months at max usage rate, 2 months at half usage rate).

Savings Analysis:

The extra usage vs my estimate is partly due to it being less of a hassle than buying it at the store, and partly due to the operational improvements (no dust, no noise, limited cleaning/no scale on the heating element). It does not include coffee maker use: I don't work from home much/drink much and didn't use it for that during the test.

I bought a Total Dissolved Solids (TDS) meter on Amazon; they're cheap, they measure conductivity. My normal softened water read is 276 ppm, and out of the RO system it reads 7 ppm. I had suspected my water softener wasn't working well before this winter so I turned off "salt saver" mode and it seems better.

Surprisingly the indoor air quality meter is still measuring particles in the air, though it's down maybe 80% (varies significantly by usage and how much my central heating runs). But you can't smell/taste it in the air or find residue anywhere. The humidifier uses a felt pad to provide nucleation sites for the boiler heating element, and it seems to disintegrate over time, so perhaps that is literally dissolving and being dispersed in the air.

I'm a big fan of how this turned out.