ResMed AirSense 10 Burn Smell

[Crimson Nape]

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[frolic]

I'm curious if anyone has noticed a correlation with the air pressure?

Without going into details of my experiments and speculations, a few things I've noticed:
- When the smell wakes me up, I will attempt to "flush" the system by created a leak: lifting the mask, disconnecting the hose, removing the humidifier tank. Sometimes this will clear the smell & it does not return, though one recent night the smell was persistant even after flushing multiple times so I went to my Plan B for that night (see below). The other helpful thing this does is that it shows up as a Large Leak event in Oscar. In Oscar, I've noticed that these events are proceeded by auto air pressure increases.
- Each night before bed, I decide what action I'm going to take if the smell returns (so I don't have to think about when awakened.) I also have a Plan B. Plan B is to switch to my AirMini I use for travel/backpacking.
- A few nights ago, none of my planned actions worked. The smell kept returning, and it was strong! Switched to my AirMini. Here's were it gets interesting...
--- First night on the Airmini was fine. I had forgot to set the pressure minimums in the clinical menu.
--- Next night, set the min pressure to 10  and other settings to match the AirSense. Put on the AirMini Mask & fell asleep. Woke up to the smell of burning plastic!
--- Last night I turned the min pressure down to 8. No smell!

A few months ago, I posted my Oscar graphs to request setting recommendations. Board members suggested that I increase the min pressures on my AirSense10 from the default 4 to 10. I think the occurrence of this smell issue is not coincidental. It currently appears to me to have something to do with the pressure, such as possibly overworking the air pump causing it to overheat.

I'm still speculating & experimenting. Some temporary suggestions:
- Remove the air filter (to reduce the air resistance)
- If the scent awakens you, vent the hose to TRY to flush out the scent. It may not work but it might provide temporary relief. If you do, look for the leak in Oscar and note the pressure graph
- With caution, if your apnea therapy allows for it, & purely for troubleshooting, consider reducing your min pressure or even limiting the max pressure.

Note: The reason replacing the hose worked for me the first time was becuase it flushed out the scent. The issue is clearly not the hose, as it eventually reoccured with a non-heated hose & a new heated hose.

[Nightynite]

Frolic, When I replaced my blower motor on my A10 I noticed the fan blades had discoloration from dust or particles that passed through the motor. My unit had less hours than yours plus I always changed out the filter every 2 weeks. Another idea in your situation is it may be the accumulation of dust or dirt and the motors heat could be causing the smell.

[SeePak]

Last night had 'the smell', light amount but i noticed it enough to shut off my machine, go for a pee and fell asleep without mask on!
No smell when i restarted 2 hrs later.

[frolic]

I wonder, how many of you have poor cell reception? Keep reading to know why I ask.

Several days ago I disassembled my AirSense 10 per the iFixIt guide:
https://www.ifixit.com/Device/ResMed_AirSense_10

The inner components, including the pump casing and pump motor, were clean, dust free and no noticeable signs of burning. However, I noticed the attached, which is the cellular modem antenna. New, it is ceramic white (you can find the part online.) It certainly appears to me to be severely discolored from heat. It is also located next to the air intake. If your cell reception is poor, the modem may be periodically using more power to drive the antenna (hence, heat & possible smell.)

While your insurance my require it, the cell modem is not technically necessary. Upon reassembly, I removed the cellular modem board in its entirety. That said, I'm still experiencing some occurrence of the scent. However, so far, it only occurs when the humidifier heat is on (even at setting 2) and even then is still a periodic occurrence. As previously posted, I can sometimes clear it by venting the hose or removing the tank for a few seconds.

I think this may be multi-causal, which may be why its been so hard to find the culprit.

You might try putting the airsense in airplane mode, in addition to turning off the humidifier and heat tube. You could also try disconnecting the cellular modem board cable from the motherboard if not removing it all together.

One thing that still doesn't make sense to me though: the max temp spec for the humidifier heat plate is supposedly 154°F (~68°C) which I think is well below the temperature plastic should emit a smell. I have seen some studies online stating detectable VOC from plastic as low as room temperature. But, I'm sure we can find studies that tell us whatever we want; this is all well outside my area of expertise. I have not seen any signs of melting or discoloration in the tank or around the heat plate. (And to be clear, I am not claiming the smell is your imagination as I am experiencing this smell myself.)

[Barney9]

Just to confirm, that I too have been plagued with this same frustrating problem.  The original AirSense 10 did similarly to what you have described.  The local supplier exchanged the first for a  second machine, and it developed the same problem within the first few days of use.  We took that machine back and they gave me a third one to use.  I've used it about three nights, and woke up this morning with a headache, nausea, and a strong overheating odor in my nose and lungs.  I have been diagnosed with severe sleep apnea, but I can't take the inhaling of this stuff, and after three AirSense 10s, I think I am through with them.

[SeePak]

I just had a light smell of the burning last night and after 1 hour of therapy I stopped not sure what's going on
it's hard to believe that machine after machine would do it for somebody seems pretty weird
This is the third or fourth time I've had this happen now and I'm pretty sure I posted about it

[frolic]

I wasn't going to post just yet because I'm still testing, but I may have sorted out the second cause on my machine: condensation from the hose escaping into the pocket that the humidifier tank slides into. I think on exhale, especially under higher pressure, condensation is pushed through the seal at the output of the humidifier tank (the 90° elbow that the hose attaches to on the machine.)

My preliminary research indicates that warm water on warm plastic can emit VOCs at a lower temp then just warming the plastic alone. "On paper" its supposed very minor, but when concentrated in the hose and directed directly to your nose its going to be stronger. But, I am not an expert in this subject!

Additional Suggestions:
- Max the heated hose temp
- Minimize the humidifier heat (I'm bumping mine up one point each night. I made it to 5 last night with no recurrence for the last several nights.)
- A thin coat of silicone dielectric grease on the seal (DO NOT USE anything other than silicone based grease) may help improve the seal.

When this occurs, see if you see any condensation inside the machine where the tank is inserted, under the air pipes.

[SeePak]

I stopped using heated humidity after somebody mentioned about the humidity and now I will stop putting water in my tank as well, which I had some in my reservoir even though I wasn't heating it the last time I had that faint smell of burning.

Thanks for the heads up Frolic.

[frolic]

Consider enabling Airplane Mode before going to sleep. Its a setting in the menu. Enabling airplane mode turns the cellular modem off. If your insurance requires calling home, disable airplane mode when you wake up so it can upload.

In mine, I think there were two sources for the smell. One of them was the cell modem antenna. Look a couple posts up for the picture from my machine. The antenna was scorched. And, its located right beside the air intake. I don't need it for insurance reasons anymore, so I just yanked the whole board out while I had it apart but hopefully enabling airplane mode is enough.

Only issue I've had since last post is my tank ran out of water in the early morning, which produces that smell also. I'm back down the level 5, for that reason. I also put the intake filter back in last night to rule-out the filter as an issue. So far, so good, no recurrence of smell, fingers crossed.

Good Luck & I hope you get some good rest!