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Old 07-25-2016, 02:07 PM
jayrey jayrey is offline
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Carbon monoxide from portable A/C unit

I have a one-year-old LG portable A/C unit -- the kind that looks like a big white bread box sitting on it's end, with a collapsable hose venting hot air out the window. The window kit that attaches to the hose is okay, but the way the hose attaches to the A/C unit itself is a joke. You are supposed to be able to "screw" the "thread" of the hose onto the "threads" of the unit but that doesn't work worth a damn. It looks okay but the minute the air begins to exhaust, the hose falls off the unit. I tried lots of options before just duct taping the hose onto the unit. It works a treat but the tape does get pretty warm. Not about-to-burst-into-flames hot, but definitely warm.

Yesterday, I had the unit on for about two hours when I started to smell -- well, all I can decribe it as is car exhaust. I would have sworn someone had vented their tailpipe into my apartment, which is not possible because I'm on the second floor. It wasn't coming from outside; the windows were closed. Just as I realized it was coming from the A/C unit, my smoke/CO detectors started screaming. I shut off the A/C unit and opened the windows (promptly losing both the cool air and the CO).

What the hell happened? Does the compressor give off CO? But CO is odorless, or am I misremembering organic chem? What in my A/C unit is causing this and, importantly, with hot weather coming fast, how do I stop it? Is the duct tape off-gassing someting? Any suggestions/advice is muc appreciated!

TL;DR: Car exhaust smell coming from portable A/C unit. What is causing it? How do I stop it?
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  #2  
Old 07-25-2016, 02:16 PM
beowulff beowulff is offline
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The only way an AC powered A/C could generate CO, would be if something internal overheated (Compressor, fan, PCB, etc.). Otherwise, there's no mechanism for it to do so.

So, it must have been sucking CO from outside, 2nd floor or not.
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Old 07-25-2016, 02:24 PM
watchwolf49 watchwolf49 is offline
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Is it possible the smoke detector part of the alarm unit went off ... something inside the A/C unit burnt ... I have no idea what the smell from car exhaust is caused by so I'm guessing ash and soot.
  #4  
Old 07-25-2016, 02:36 PM
troub troub is offline
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Quote:
Originally Posted by jayrey View Post
my smoke/CO detectors started screaming.
Are these combination detectors? I understand there are some that are smoke/CO combo units. So, which was it that set them off? I imagine there's a different tone or something based on whether it was smoke or CO.

I don't think these units suck in air from outside; the window kit is just for the hot exhaust.

So, my theories would be: the tape either got hot enough or deteriorated over the time it's been on there and is off-gassing something that smells and trips the smoke alarm; or a component of the unit is actually failed and/or overheating and generating either smoke or CO (if it's possible to generate CO that way). And yes, CO is odorless, most of the car tailpipe smell is related to compounds from oil/gas/petrochemical stuff...which again makes me think it's smoke, rather than CO, but it could be from the tape or some plastic/wire insulation/PCB/etc burning inside the AC. Little way to know aside from turning it back on and trying to find the source (if you can see smoke anywhere, or if the tape smells, process of elimination/induction)....Have a fire extinguisher handy, just in case.

Last edited by troub; 07-25-2016 at 02:37 PM.
  #5  
Old 07-25-2016, 03:25 PM
jayrey jayrey is offline
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Quote:
Originally Posted by troub View Post
Are these combination detectors? I understand there are some that are smoke/CO combo units. So, which was it that set them off? I imagine there's a different tone or something based on whether it was smoke or CO.

I don't think these units suck in air from outside; the window kit is just for the hot exhaust.
Yes, they are combination alarms (required because the apartments have gas appliances), but I have never heard any difference in sound between smoke (from a too hot pan on the stove) and CO/radon detection.

You are also correct that these units do not draw air in from outside. They draw in air from the room(s) and it flows over a condenser to chill it.

There was no smoke present anywhere, no smell of burning wires, just the very strong odor of car exhaust.

I am becoming more and more suspicious of the tape. Between whatever petroleum product the tape itself is made of, and the adhesive on it, I bet there's something nasty off-gassing.

So how do I attach the hose to the unit without using tape? The hose fits inside the the fitting on the unit (male into female). If the hose fit over the flange, I could cinch it on with cotton string. But the hose goes inside, not around the outside. Ideas?

Thanks, everyone!
  #6  
Old 07-25-2016, 03:26 PM
Machine Elf Machine Elf is offline
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Possible your AC unit has a refrigerant leak? According to this discussion, older CO detectors operated at high temperature and could give a false positive when exposed to hydrocarbons or other chemicals that produce CO when heated.

If your CO detector is old, perhaps try replacing it with a new one to see if it behaves better.

If you think the duct tape is somehow causing the problem, replace it with a hose clamp from the hardware store (if you can't find one long enough, you can daisy-chain them together to make a clamp long enough for any diameter of hose). The duct tape residue (assuming it isn't totally baked/dried on) can be removed with lighter fluid, Goo-Gone, or Goof-Off (also from the hardware store).
  #7  
Old 07-25-2016, 03:29 PM
Machine Elf Machine Elf is offline
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Quote:
Originally Posted by jayrey View Post
So how do I attach the hose to the unit without using tape? The hose fits inside the the fitting on the unit (male into female). If the hose fit over the flange, I could cinch it on with cotton string. But the hose goes inside, not around the outside. Ideas?
Missed this. Try aluminum foil tape. The adhesive stands up to high temperatures better than duct tape.

Last edited by Machine Elf; 07-25-2016 at 03:29 PM.
  #8  
Old 07-25-2016, 03:31 PM
watchwolf49 watchwolf49 is offline
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Is it possible to snip the hose a bit so it will slip over the flange, then bind it with bailing wire or string. I would also make a complete visual inspection of the unit inside and out. I think overheated duct tape and car exhaust smell is a long shot. Let me guess, the A/C warranty ran out yesterday.
  #9  
Old 07-25-2016, 03:55 PM
jayrey jayrey is offline
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Oh, yes, I'm quite sure the warranty expired ten minutes before the smell started. Isn't that always how it works?

I will try snipping the hose to see if I can fit it over the flange. The hose clamp is a great idea. If that doesn't work, I'll look for aluminum foil tape.

The smoke/CO detector is new, installed about three months ago, replacing an older unit.

I'm also going to talk to my landlord, who is very approachable, to see if anyone else has reported a similar problem. Several other residents have portable A/C units.

If anyone else has any ideas, please don't hesitate to chime in!
  #10  
Old 07-25-2016, 04:21 PM
jz78817 jz78817 is online now
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do the detectors actually tell you whether they're activating due to CO or fire? or just alarm? it also would depend on what kind of smoke detector they are. Ionization-type (the most common, and the ones with a tiny bit of radioactive material in them) trigger based on the ionized products of combustion (flame.) they're the ones you're always setting off from cooking, even without visible smoke. Photoelectric detectors trigger based on smoke particulates.

the only thing I can think of that an A/C unit would emit to trigger a detector would be if there was some electrical arcing going on, say, in a fan motor or something. electrical arcs also produce a pungent smell as well as form ozone among other things.
  #11  
Old 07-25-2016, 04:34 PM
TSBG TSBG is offline
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Not sure I understand--my fault no doubt--but if the hose fits OVER the flange/fitting, why couldn't you use string or wire to cinch it on?

If the hose goes INTO a socket, I see your problem. I have three of these units and the flexible exhaust hose is flimsy stuff, tends to tear when I screw it into the unit or the window fitting, but I've always managed to make it work.
  #12  
Old 07-25-2016, 06:08 PM
watchwolf49 watchwolf49 is offline
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Quote:
Originally Posted by jz78817 View Post
[snip] ... the only thing I can think of that an A/C unit would emit to trigger a detector would be if there was some electrical arcing going on, say, in a fan motor or something. electrical arcs also produce a pungent smell as well as form ozone among other things.
This is main worry ... car exhaust smell and burning electronic component smell aren't that different ... there's not one thing in an electric A/C that will produce CO ... except if it's on fire.
  #13  
Old 07-26-2016, 11:53 AM
jayrey jayrey is offline
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Thanks again for all the help and suggestions yesterday. Last night, I removed as much of the exterior of the unit as I could, looking for anything burnt. It's a bit of a black box; everything really important is almost impossible (or too daunting for an amateur like me) to get to. However, I did not see or, more importanty I think, smell anything burnt. I removed the duck tape from the hose, cleaned off the little residue and replaced it with aluminum foil tape, which is very cool stuff. Then I ran the unit for an hour and a half. No smell, at all. And, the aluminum foil tape was actually cooler to the touch than the duck tape had been.

I'm we have solved the probem. Straight Dope to the rescue, once again!
  #14  
Old 07-26-2016, 11:58 AM
billfish678 billfish678 is offline
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Quote:
Originally Posted by Machine Elf View Post
Missed this. Try aluminum foil tape. The adhesive stands up to high temperatures better than duct tape.
Be careful handling that stuff though. The edges of that stuff can slice you up.
  #15  
Old 07-27-2016, 11:51 PM
oregongrown oregongrown is offline
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Portable air conditioners suck. Literally. They suck air out of your home. Some gets pulled over the condenser then blown outside and some over the evaporator and blown into the room. This action makes a negative pressure in the house or apartment. Of course it is going to get air from somewhere so it pulls hot air thru door and window seals. Think cars idling outside or a car that's just pulled into the garage. It will also pull air backwards from vents. Think gas hot water heaters, heaters with pilot lights and gas dryers. Although it could have been the tape it also could be one of these as well. If you ever buy another air conditioner get a window unit or a duel hose portable unit. The duel hose pull air from outside then send out again reducing the negative pressure problem. Way more efficient than a single hose system. Cheers
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