The CO detector goes off. Probably bad batteries, but let's get everyone outside just to be safe. Then you put brand new batteries in, and it still goes off. You have a carbon monoxide leak.

Again, you make sure everyone is out of the house, pets too (if you have the time).

Now, who do you call, and how do they normally proceed? 911 seems obvious, but in this scenario, no one was injured and so 911 might be overkill. Local fire department seems like a next-best alternative, but I live in a small town and I'm not sure if they would know what to do next.

Obviously, you need to find the source of the leak, and then call in the right contractor (furnace/heating system technician, etc.). But you can't call the right contractor until you know the cause of the leak. And if you can't even go inside your home, then how do you find the source of the leak?!?

So, who ya gonna call?

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    Don't call 911. If everyone's outside, there's no emergency. Call an HVAC service specialist and make them very aware of the presence of CO. – isherwood Sep 30 '16 at 19:11
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    How many fuel sources do you have and where are you burning things? My house only uses natural gas, and the plumbers around here do gas and HVAC, so there's really only one kind of contractor for me to call. – Comintern Sep 30 '16 at 19:11
  • Thanks both isherwood & Comintern (+1 for both) - this is not my field, so I'm not sure how many sources of CO can exist for a given home, let alone my own. I see what you're both saying, but not entirely sure that I'm bought on the concept of defaulting with my heating contractor (fuel oil), unless that is literally the only possible thing in my house that could emit/leak CO. – smeeb Sep 30 '16 at 19:16
  • Any HVAC contractor should have CO tester to isolate the leak. Not sure some plumbers would. You're pretty limited to furnace, stove, water heater, dryer or fireplace so shouldn't take them long. – topshot Sep 30 '16 at 19:19
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    @smeeb -- any combustion appliance can emit CO if it is improperly used or maintained. (If you have a house with no combustion appliances and you're still setting a CO alarm off, that's a sign that there's a smoldering fire somewhere in the house (!!!!)) – ThreePhaseEel Sep 30 '16 at 22:09

The fire department is the appropriate place to call for a carbon monoxide situation. I would call their non-emergency number and ask them to come by at their convenience. If you are in a building with other occupants it's possible the situation is caused by something elsewhere.

FYI most carbon monoxide detectors have a limited life (~7 years). There should be an expiration date on the back. Older CO alarms were extremely sensitive, e.g. to a puff of cigarette smoke or a little bit of fumes from a gas stove. Modern ones have a time-delay function where they will wait a bit, depending on the level they detect.

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    @isherwood: if you have no idea where the CO is coming from, the fire department is the safest thing. They have equipment to detect CO presence with much greater accuracy than the $15 smoke/CO detectors at Home Depot. Also the CO may be caused by an unknown fire or malfunctioning appliance and the fire department can help resolve. I would not call 911 and make a big fuss, but this is the kind of routine thing fire departments do all the time. – Hank Sep 30 '16 at 19:19
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    Fire Departments have the correct breathing apparatuses to enter the building without putting themselves in danger. They will also have large ventilation fans to evacuate the CO from the building. This would make them a good first choice to call, and I think they would also know who else, if anyone, you need to contact. CO has to come from somewhere, and in a residence one of the most likely sources is a furnace or stove. The FD can safely enter and turn off the natural gas supply, which stops any new CO from being produced. HVAC repair can then test the furnace & repair if needed. – Folk Sep 30 '16 at 19:20
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    If you call them, be prepared to have them tag your home as "uninhabitable". Get a hotel room lined up. – Jimmy Fix-it Sep 30 '16 at 19:57
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    My fire department has professional gas and CO meters to check for this very problem. I would give them a call. – bib Sep 30 '16 at 20:10
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    Definitely call the fire department, but I wouldn't be worried about calling 911 either. A CO leak is an emergency, IMO, since you can't see it, smell it, or taste it, and it will kill you if you breathe too much of it. I was in a similar situation a couple years ago, and called 911. Turns out my CO detectors were at end of life. – mmathis Sep 30 '16 at 21:03

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