ResMed AirCurve 10 VAuto Burning Smell

[ajack]

I have tap water in 2 Litre bottle and just top up the reservoir. Keep it full and don't let it run dry. I rinse the tank when I fill the bottle. A take apart and soak with vinegar is occasionally, when the plastic gets cloudy. I do the hose then as well. I'm still alive.

It's just your normal environmental stuff. what's in the tank doesn't reach the mask anyway.
https://www.ncbi.nlm.nih.gov/pubmed/16236866/
Sterile water is unnecessary in a continuous positive airway pressure convection-type humidifier in the treatment of obstructive sleep apnea syndrome.
The convection-type humidifier produces water vapor but does not aerosolize the water. We conclude that bacteria, other microorganisms, or even solutes that may be contained in the water cannot be transported into the air and thus will not be deposited in the lung. In order to avoid respiratory tract infections, sterile water is not required, at least in this particular humidifier. We suggest that nonsterile tap water is probably a safe alternative.

[Apnearon]

I've been using my ResMed AirCurve 10 VAuto for about 3 weeks now.
Last night I awoke to smelling burning plastic inside my mask!
It looks like I'd forgotten to top up the humidifier reservoir last night, and it had run dry.
I normally have the humidifier on full, so I have to refill the reservoir every night.
How come the humidifier no has over-temperature cut off? 
And how come there were no warnings on the display that the reservoir was dry?
There are no visible signs of burning plastic, so I don't think the device is damaged.

I can't seem to find any way to report this problem to ResMed. Any suggestions?

Are you a smoker? On three occasions I’ve had the same problem as you described, burning  smell in the mask, since I’m a smoker I’m thinking that was what is causing my burning smell, it has only happened 3 times so far.