I have a few Cadet wall units in my house. (These are about 12x8 in units mounted in the walls.)

One of the units has a built-in thermostat and a knob to adjust the temperature.

I don't know how old the unit is.

The strange thing is that often after running for a while the unit starts making a hissing noise. Not a buzzing but something higher pitched, like as if steam were being released from a valve. (But I don't believe there is any liquid involved here.)

My best guess is that the hissing happens when the temperature reaches and thermostat value, so the heater turns itself off, but then some other mechanism with different calibration decides it still needs to be on. And it goes back and forth very quickly. But event then I would expect to hear a bunch of fast clicking sounds, not a hissing sound. (One other detail of the hissing is that when it's in that state it can mess with my computer mouse -- like the mouse doesn't work, and then I adjust the thermostat to stop the hissing, and then the mouse works again. So there is some electrical strangeness happening.)

So one question is where the hissing comes from.

But the more important question for me is that I was recently diagnosed with a life-threatening form of sarcoidosis. It's too late to undo that now, but for sanity's sake I'm trying to understand if this misbehaving Cadet heater was partially responsible for my illness. They don't know what causes sarcoidosis, but among the few possible triggers they list are various types of inorganic dust, especially metallic dust.

So the real question is whether this hissing heater could have been spewing out aerosolized bits of metal that I was then breathing in. A friend says the heat would not be enough to break off tiny pieces of metal, but I don't know.

  • 3
    I’m voting to close this question because this question is not about Home Improvement. The OP is researching potential causes of a personal medical condition. Feb 23 at 2:21

A short or arcing would most likely sound more like a buzzing (but could sound like a hiss, I guess) but would also be accompanied by smoke, a nasty "fried circuitry" ozoneish smell, and black soot marks near the source. I have never heard of this being a common source of danger for anything besides fire and/or shock.

I think it is way more likely that the noise you are hearing is a vibration; one that just happens to happen at a certain point of operation and coincides with a frequency that interferes with the wireless signal from your mouse's transmitter and the receiver unit.

Occam's razor: the most likely solution is almost always the solution. Take the grille off and tighten every screw you can find, whilst also looking for any signs of arcing or electrical failure.Either way, I doubt those little Cadet heaters are the cause of your illness (which I am sorry to hear about and hope you find health and happiness).

  • Yes, there is no smell, just the hissing sound.
    – M Katz
    Feb 21 at 1:16
  • The mouse is a wired mouse.
    – M Katz
    Feb 21 at 1:18
  • Could you say a bit more about "I doubt those little Cadet heaters are the cause of your illness"? Given that there is never a burning smell, just this occasional but common hissing, It sounds like you're saying it's not a short or arc. But could it still be something that would release nanoparticles of some metal? Enough that if you worked right next to it for over a year could do some damage to the body?
    – M Katz
    Feb 21 at 1:38
  • "Could it... be something that releases nanoparticles of metal?" How do you expect an answer to that question when you (and us) have no idea what the actual source of this hissing sound is? The answer is... maybe but probably not. Industrial processes (e.g. welding, arc gouging, grinding, plating) are the places where airborne metallic particulates are a concerning problem. Feb 21 at 7:35
  • See here for what the hissing is: physics.stackexchange.com/a/616142/289738
    – M Katz
    Feb 21 at 15:54

It sounds a lot like an arc fault, this could produce nanoparticles (but I would expect metal oxide or nitride nanoparticles), but more importantly it's a concentrated heat source that will damage your equipment and may cause a fire.

Your heater may need the thermostat replaced. or it may just be a loose connection to the house wiring.

  • Not all arcs are faults. Infact cadet heaters use bimetallic thermostats almost exclusively and it may be possible a old set of contacts is arcing as they start to separate. Since the op did not smell Ozone and yes our noses detect it it was not at a harmful level in my opinion.
    – Ed Beal
    Mar 7 at 21:04
  • if it's an audible hiss it's continuous, functional contacts only arc briefly.
    – Jasen
    Mar 7 at 23:13
  • the op stated after not running for a while. I have replaced many contact sets from heaters especially if one of the contacts is just about gone or making contact with the metal of the spring under the contact there is a arc and to some it sounds just as the op described. Contacts commonly create balls of contact materials that as current is passed the ball melts back into the surface, large contacts are full of these and work fine for years doing this.
    – Ed Beal
    Mar 8 at 14:14

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