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Burning Smell?
Burning Smell?
Hi I'm new here.  I am not new to CPAP use.  I am wondering if I am having a burning smell with my ResMed AirSense 10.  It is less than 2 years old and used an avg of 12 hours a day.  I have not inquired with DME yet.  I did see at least one other thread here with the same subject matter, however, but here is another.  I will also post progress and any technical results/determinations received from Manu and DME along the way.  The problem is intermittent at this time so I am not sure yet how my investigation will progress.  Warranty may force a look real soon.  And obviously IT'S STARTING TO GET ANNOYING OR I WOULD NOT BE DOING THIS...  So, for now here goes...

My issue is that I am suspicious that I am smelling a slight burning smell with this unit.

1) Unit is AirSense 10 less than 2 years old and used daily.  Sometimes longer usage as I will wear it whenever laying in bed doing work of the laptop even when awake.  Pressure settings about 8-10.  For Humidifier I use bottled water from Costco.

2) I use nasal pillow type mask usually Swift FX.

3) I have not pulled any data that is being reported to DME at this time/ never have tried.

4) My hose is currently just a regular hose because the fancy "Anti-Rainout" one that came with it got damaged and I have not replaced yet.

5) So, I have the humidifier on the unit and use it on a manual setting around 5-7 (don't recall but a little past half way). 

6) The unit is operated in clean and stable conditions and rarely moved.  Maintenance only to clean water reservoir as required, which is once every 2-3 weeks.   To clean I scrub and soak with cleaning grade vinegar and soft paper towel, and then follow up with a hydrogen peroxide dousing. If any slime remains in crannies after all that, I have been known to douse it with some bleach for a min or two.  

7) The machine seems to be working as intended otherwise.  I have no complaints at this time regarding it helping me breathe when sleeping.  This is also a QUIET MACHINE you can not hear it operate at all.  The breathing routines seem to work perfectly and I never feel any adverse or incorrect air pressures.

* What I smell is similar but not identical to the time i let condensation from a drink build up on top of a (past machine) Phillips Resperonics.  FYI liquid comes down the hole in the top cut for the dial and shorts the board.  Note to self...  Using Philips SA device for drink coaster is A NO NO....  LOL

* I am NOT ruling out mold in air hose at this time will clean today.

* I am worried that ResMed has used a really small fan motor for minimal noise and that I am overworking it with my long periods of use...??  !!  ???  And i would hate that cause I really LOVE this machine its my first Resmed.

Does anyone have any thoughts for now...?
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RE: Burning Smell??
Most likely it's the power brick your smelling. Best to keep it on the floor away from the bed. It's a pretty common question that pops up.
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RE: Burning Smell??
The most common cause for a burning smell is operating the CPAP in close proximity to the power adapter brick. Tje adapter ismpotted with an epoxy and has an odor when it gets hot.
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RE: Burning Smell??
Power supplies don't last forever, and some of them are downright dangerous from the outset...leaving the factory.  They all get warm, sometimes plenty warm, but they should never be alarmingly hot.  It may be that you are smelling the hot casing, perhaps a warm cord, or the hot surface on which they rest (carpet, plastic), or maybe something in the water in the reservoir...although that last one is doubtful.

If the hose is bothersome for some reason, and you can't seem to find any evidence of mold or other contaminants, I would soak the hose's interior with a solution of baking soda (sodium bicarbonate) for an hour.  Rinse it well, and maybe you will have solved the problem.

Motors arc somewhat, and when they do, they produce ozone.  Ozone is best avoided because it is highly reactive, particularly with organic material...our nasal interior, the inner surfaces of the hose and mask.  Some people can detect ozone in minute concentrations.  I don't want to alarm you because the generation of ozone in our devices should have been engineered OUT, and the risk of it should be exceedingly small to negligible.  But...maybe...this is what you are smelling.

These things have circuit boards.  They all handle current and can get warm.  They have materials that, when over hot, can start to produce volatiles.  It's possible that you are smelling this.  Again, the chances of this are meant to be exceedingly small, but it can happen.  The components all come from the lowest bidder who meets the specifications.
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RE: Burning Smell??
Determine where the odor is coming from. Are you running out of water? If not, and the odor is coming from your machine, contact DME. Sometimes the modem overheats and will potentially wreck the rest of the board, so best to get this sorted out right a way. If it is coming from the brick, feel the brick. If very warm, contact DME. You need a new one.

Above was from the service tech. In my case, it turned out that I was running out of water and hadn't really realized that because it hadn't happened in the previous 3 years I owned the machine.
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RE: Burning Smell??
(12-04-2018, 10:56 AM)BC3B Wrote: Maintenance only to clean water reservoir as required, which is once every 2-3 weeks.   To clean I scrub and soak with cleaning grade vinegar and soft paper towel, and then follow up with a hydrogen peroxide dousing. If any slime remains in crannies after all that, I have been known to douse it with some bleach for a min or two.  

Seems like not such a great approach.  Two to three weeks isn't often enough, and as for bleach ... you want to be breathing that crap?  "If any slime remains"? Say what?  Why is there slime to begin with?  Because you waited three weeks to clean it, leaving water in the tank the whole time so slime could grow?

Sorry, but the phrase "Folks, this ain't rocket science" comes to mind.


You should clean the device weekly as described. Refer to the mask user guide for detailed
instructions on cleaning your mask.

1. Wash the water tub and air tubing in warm water using mild detergent.
Do not wash in a dishwasher or washing machine.
2. Rinse the water tub and air tubing thoroughly and allow to dry out of direct sunlight and/or heat.
3. Wipe the exterior of the device with a dry cloth.

Do not use bleach, chlorine, alcohol, or aromatic-based solutions, moisturizing or
antibacterial soaps, or scented oils
to clean the device, the water tub, or the air tubing. These
solutions may cause damage or affect the humidifier performance and reduce the life of
the products.

I'm not saying that you have to follow the instructions to the letter, but OTOH being even more careful than that is a good idea, for instance removing the tank every morning when you get up, emptying it, and then leaving it open to air-dry, maybe after wiping the inside of it with a paper towel.

But this doesn't have to do with a burning smell, sorry.  It does have to do with a moldy smell, though.

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RE: Burning Smell??
Interesting thread and posts. I checked my power adapter and it's only slightly warm to the touch. If even that. Never once have I experienced any burning smell. But.....if I do, I now know where to look. 

As far as cleaning the water reservoir goes, no way I'd wait a couple of weeks. Of all the equipment that needs cleaning, it's one of the easiest pieces to do. 

I don't even like leaving standing water in it from the previous night.  Oh-jeez
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RE: Burning Smell??
Thank you all for the replies so far and this is where I am with it.

I used the cpap again this afternoon after not wearing it for a few hours.  I noticed the smell was gone.  Then it came back in 5 mins or so.  Its a definite smell...  I am leaning with an overheating board at this point, but..  I am really hoping I have not been laying around sucking down burnT PC board fumes again..!?!?!??!

I have since cleaned EVERYTHING, but not yet tested again.  There was nothing more than light intermittent clear slime in the bucket.  Very light.  But there was no telling what was in the hose cause you can't see down in there.  It has been pretty wet in recent past weeks I recall and could have had a jungle growing in it for all I know...  But the hose did not really have any smell so unless it activates when the hot air goes thru there I just dont think so.  I had one years back that I never cleaned the hose on as I used to break em every six months stepping on them..  this hose was note heated, but only 3 months old.

I will check power supply tonight.  I don't think it is the case as it sits way down on hardwood floor and I would think I would smell that all over the room.  It does remind me that I do have a laptop power supply that gets hot down at the foot of the bed and its on whenever I am in it.  So...  Hmmm.  It's just not all in the air like you would think if the supply was an issue.   and its coming out of the hose - plain and simple...

Spoke with DME and we can send it to Manu for inspection if persists.  I will report back tomorrow...

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RE: Burning Smell??
(12-04-2018, 07:40 PM)BC3B Wrote: But there was no telling what was in the hose cause you can't see down in there.

Just in the department of FWIW, hoses of the non-heated kind are inexpensive and it's always a good idea to have at least one spare. For instance, I just tried an Amazon search for "cpap hose" and sorted by price, and the first one that came up is less than $7.

But from what you've said, it seems like the smell originates inside the machine.
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RE: Burning Smell??
It amazes me that in America there are no OFF switches.
Everything just runs 24 hours a day unless it has its own off switch.
It is no wonder the power supplies get hot and smelly running all the time.
OFF in a lot of appliances these day is not off but a stand-by mode.
Think of the bills you could save if you had off switches that killed the power to everything that is not being used.

It is most likely the power brick. I have notices that the Swift fx nasal pillows if not washed for a few days get a sort of hot almost burning smell.
It is just the silicone reacting, a good wash and it goes away. It only appears to be the pillows themselves that picks up this smell, it is just a hint, but noticeable. But best way is to unplug the power brick when not in use. If the data from your machine get downloaded, tough, they can look at the data card when you go, or leave it on for an hour after use, then unplug it. It would not be allowed to be left plugged in here without it being on a switched socket.
I am NOT a doctor.  I try to help, but do not take what I say as medical advice.

Every journey, however large or small starts with the first step.

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