AirSense 10 Humidifier badly discoloured after first use

Shocking... I'm late to this post but I've never heard of anything like that before. As others have said, I'd suspect the manufacturing process... it's good ResMed was told about this.

palerider wrote:there are three s9 containers, original, cleanable, dishwashable.

the cleanable and dishwashable look pretty much the same.

I believe that in ResMed S9 technology, "cleanable" and "dishwashable" are the same thing. ResMed tends to use the word "cleanable" and sellers tend to say "dishwashable.".

The cheap tank is called "standard." Older S9 standard tanks were not designed to be opened, but you could do it with some effort. The newer standard tanks were openable, but cheaper than the "cleanable/dishwashable" versions.

archangle wrote:

palerider wrote:there are three s9 containers, original, cleanable, dishwashable.

the cleanable and dishwashable look pretty much the same.

I believe that in ResMed S9 technology, "cleanable" and "dishwashable" are the same thing. ResMed tends to use the word "cleanable" and sellers tend to say "dishwashable.".

The cheap tank is called "standard." Older S9 standard tanks were not designed to be opened, but you could do it with some effort. The newer standard tanks were openable, but cheaper than the "cleanable/dishwashable" versions.

yup, original standard (36802), replacement standard (36803) and cleanable (36800)

I'm not sure this is a defect, other than a customer perception issue.

Both stainless steel and aluminum form a thin, transparent oxide layer on the surface of the metal. This oxide layer is what prevents further corrosion.

Depending on the thickness of the oxide film, it may produce some optical effects like an oil film on water. If the thickness of the film is right, there are optical interference effects at certain wavelengths of light that produce colors. While it looks unattractive, that oxide layer is there even if you can't see it. It's fairly common for a rainbow effect like this to appear in stainless steel pots, and it doesn't seem to cause any problems even in cooking or food prep applications.

Of course, customer perception is important. It could also be a symptom of something other than normal oxide discoloration.

I would think to get that hot to discolor the metal the water must have been boiling up a storm. But no one has mentioned a steam bath effect.

This does look like the iridescence seen on the surface of rainwater that has fallen on a road.
A microscopic layer of petroleum products refracts light just enough for a colorful display. Pretty, too.
I still cannot imagine this to be an intended result.

No doubt about it, a major hot spot is forming and as a result you're getting thermal spalling. Either the heat is all being generated in one spot, so a faulty heating element, or the metal isn't spreading the heat throughout the metallic volume correctly or fast enough so it is building up in one spot and damaging the metallic structure. If its the later, it's either a fault in the alloying of the metal, so a fundamental flaw in their alloy formula, or the application of the metal to the container, so an assembly/construction defect.

It shouldn't be too difficult for them to figure out, they just need to take a look at one of the defective tanks. A few bench tests will tell them what the culprit is.

You usually get this kind of optical banding effect two ways, mechanical strain or oxidation. If it's due to mechanical strain from inappropriate thermal expansion/contraction, eventually the metal will fail. I find it hard to believe its intended oxidation, that would mean the metal is directly chemically reacting with the water itself when enough thermal energy is applied and is progressing over time. That should never happen if its constructed properly. The metal in medical devices are supposed to be inert, either inherently or by processing means. Also, the color banding indicates variable oxide thickness, each color is a different thickness of surface oxide formation, which would mean its an uncontrolled oxidative reaction, and that doesn't seem right, as one would always want a consistent oxide layer thickness if that's the intended outcome.

I would say, by the fact that the ResMed people have not seen it before, and that they are sending a replacement, even if it is just metallic oxidation resulting from the thermal energy applied, this is not meant to happen. If this was expected to happen they would have known about it from product testing/QA and just told the OP "Oh yeah, this oxidation happens. Its normal, don't worry"

TangledHose wrote:This is all very interesting Dave, especially since your damage occoured with the dishwasher safe tub, that surprises me - be sure and keep us updated, I am curious to see what ReaMed says about your issue.

Thanks, I definitely will keep you all updated, it is worrying that this is happening on the dishwasher safe tubs, I'm hoping its just a manufacturing defect on the tubs and not actually the machines, that would be more of a problem to fix.

archangle wrote:I'm not sure this is a defect, other than a customer perception issue.

Maybe you're right but this shouldn't happen in a medical machine, and certainly nobody would be happy if you're paying $1000 like I did for the machine for it to be doing this, when you've had the H4i and H5i on previous machines, I've had all in all 4 different humidifier water chambers, none have developed hotspots / corrosion like this in the last 10 years.

chunkyfrog wrote:This does look like the iridescence seen on the surface of rainwater that has fallen on a road.
A microscopic layer of petroleum products refracts light just enough for a colorful display. Pretty, too.
I still cannot imagine this to be an intended result.

Yes I would agree, what you would see when water hits tarmac and you get that oily colour. It's strange though as it didn't go that colour in the first couple of days but continued usage has now turned the damage to that. I'm still waiting for the replacement, hopefully it will arrive today and I can then start seeing if the replacement fixes it.

Paralel wrote:No doubt about it, a major hot spot is forming and as a result you're getting thermal spalling. Either the heat is all being generated in one spot, so a faulty heating element, or the metal isn't spreading the heat throughout the metallic volume correctly or fast enough so it is building up in one spot and damaging the metallic structure. If its the later, it's either a fault in the alloying of the metal, so a fundamental flaw in their alloy formula, or the application of the metal to the container, so an assembly/construction defect.

Thanks, so it does kind of sound like the machine may be at fault and causing the thermal spalling, because if the metal was uniformed thickness then in theory the heat should spread across the metal, unless of course there's more of a contact point at one part of the water chamber, e.g a pit / point that touches the metal plate in the machine more, but the base is flat so I doubt that would be the cause. This then brings it back to the machine maybe being at fault.

That said, others are also experiencing the same problem but no where near as bad as mine appears to be, so I'm really hoping it's just a failure in the manufacturing process of the water chambers, and that might show the difference as to some not being affected, some being affected but only a little and some like mine being massively affected. It's entirely possible its down to batch numbers of the water chamber.

Paralel wrote:Also, the color banding indicates variable oxide thickness, each color is a different thickness of surface oxide formation, which would mean its an uncontrolled oxidative reaction, and that doesn't seem right, as one would always want a consistent oxide layer thickness if that's the intended outcome.

Yep that definitely lends itself to a manufacturing defect when they're making these water chambers.

Paralel wrote:I would say, by the fact that the ResMed people have not seen it before, and that they are sending a replacement, even if it is just metallic oxidation resulting from the thermal energy applied, this is not meant to happen. If this was expected to happen they would have known about it from product testing/QA and just told the OP "Oh yeah, this oxidation happens. Its normal, don't worry"

Yes you would definitely hope this would have been picked up in the QA process. Hopefully it's not toxic in any shape or form although I did find an article on Metal toxicity that suggests "Metals in an oxidation state abnormal to the body may also become toxic:". Fingers crossed it's definitely not harmful in any way.

The discoloration itself is only a cosmetic problem. The issue is that one of the more likely sources of the spalling is that the heating element is getting hotter than it is designed to do. That would be more than a cosmetic problem.

Nick Danger wrote:The discoloration itself is only a cosmetic problem. The issue is that one of the more likely sources of the spalling is that the heating element is getting hotter than it is designed to do. That would be more than a cosmetic problem.

Thanks, let's hope so.

Good news is I have now received the replacement (again) dishwasher safe tub, so will be trying this tonight, but photo taken ahead of use just in case second tub develops similar hotspots. Any marks on the tub photo below are just reflections, inspected fully and looks perfect in normal light.

After well over a month with distilled water, my tub (C) is still flawless.
Could Resmed be all wet about using tap water?
I use distilled water because I have seen the water quality reports for Lincoln.
It is hard, very hard, and contains enough minerals that an old toilet tank looks like a limestone cave,
and shower heads/lawn sprinklers get unusable very quickly unless they are delimed frequently.
Dave21, in your place, I would go back to distilled water, unless others are getting discoloration with that too.

Chunkyfrog, I used to use distilled water for a couple of years and was then told by ResMed UK that it really doesn't make a difference and as distilled water isn't easy to get hold of (and expensive) in the UK and ever since ResMed UK recommend regular tap water to be used. For the last 7 years I've not seen any difference between regular tap water and the 2 years of using distilled water other than you need to clean the tubs a little more frequently due to scale build-up on the side walls. ResMed UK still recommend regular tap water over distilled tap water.

Others I believe from reading on this thread have also used distilled water and had similar issues (although not as bad) so I don't think it will make any difference to the tub. My bet is that there are a batch (maybe first/early batch) of tubs that were rushed and weren't finished/coated correctly and those have exhibited the problem, maybe additional batches are fine. Likewise for those that have had replacement tubs, they haven't had any problems, which would kind of rule out the machine being at fault and likewise I don't believe they've switched between the water type (regular vs distilled) they were using.

In nearly 5 years on the S9 I've never had any discolouration or marks the inside base of the dishwasher safe tub, I may get scale marks up the side walls where the water line tends to sit over time and on the inner plastic tray that sits on top of the tub with the water line gauge, but that's all I've ever had with regular tap water and replace my tubs within 2 years. Even at the 2 year mark the S9 H5i tubs have never had any discolouration, the inside base has been immaculate still after that duration, so regular water really shouldn't do this damage to the tubs, and especially not after 1 night or 9 hours of use. Either way for that damage / oxidation to occur, there has to be a fault either in the humidifier or the tub manufacturing.

It sounds like you have nailed it, unless there has been recent changes to your local tap water.
I suspect our water is more wonky than what you folks get, which is why the idea entered my little green skull.

chunkyfrog wrote:It sounds like you have nailed it, unless there has been recent changes to your local tap water.
I suspect our water is more wonky than what you folks get, which is why the idea entered my little green skull.

Yeah our water in the UK isn't that bad, some areas it can be quite hard but where I am it's about medium. I've had a kettle for 10 years and it still has relatively no limescale on it.

I just hope it's a bad batch of tubs that maybe they needed to scale up production quickly so were rushed and they didn't get the full treatment on them as opposed to the AirSense 10 machine. If it's a faulty machine that can heat up more than it should randomly or sometimes permanently when on, that could be more of a problem for ResMed to fix.

Here's hoping there's no corrosion/marks/oxidation after using it tonight, I'll post some pics tomorrow either way then follow it up 5 days later just to see if that then cures the problem. Fingers crossed!

For those resmed fans who have an interest search this forum or google using "SteriCycle resmed recall". circa 2007