{
  "title": "Carbon Monoxide Alarm Going Off — Who Do I Call?",
  "description": "CO alarm sounding? Get everyone outside, then call 911 or your gas utility — both respond free with meters. What triggers it, and when it's safe to return.",
  "category": "gas",
  "vertical": "hvac",
  "tldr": "Get everyone — including pets — outside into fresh air right now. Then call 911 from outside. The fire department responds to CO alarms free of charge and carries meters. If anyone has a headache, dizziness, nausea, or confusion, say so on the call: that's CO poisoning and it needs medical treatment. Do not go back inside until you're told the level is safe.",
  "who_to_call": [
    {
      "who": "911 (fire department)",
      "when": "Any sounding CO alarm, and always if anyone feels unwell — they respond free and carry meters",
      "not_for": "The alarm is chirping once a minute — that's a low battery, not CO"
    },
    {
      "who": "Your gas utility's emergency line",
      "when": "You suspect a gas appliance and nobody has symptoms — most utilities also respond free, 24/7",
      "not_for": "Anyone is symptomatic — call 911 instead, it's faster and they can treat"
    },
    {
      "who": "HVAC technician",
      "when": "After the emergency is cleared — to find and fix the source (usually a cracked heat exchanger or blocked flue)",
      "not_for": "Before responders have confirmed the house is safe to occupy"
    },
    {
      "who": "Chimney sweep (CSIA-certified)",
      "when": "The source is a blocked or damaged chimney, flue liner, or fireplace — most HVAC companies decline masonry work",
      "not_for": "The fault is inside the furnace itself"
    },
    {
      "who": "Plumber",
      "when": "The source traces to a gas water heater's venting or draft hood — in many areas water heaters are a plumbing license, not HVAC",
      "not_for": null
    },
    {
      "who": "Your landlord (in writing)",
      "when": "You rent — working CO alarms and safe appliance venting are the landlord's legal duty in most states",
      "not_for": null
    },
    {
      "who": "Poison control (1-800-222-1222)",
      "when": "For guidance on symptoms and exposure, alongside emergency services",
      "not_for": null
    }
  ],
  "body_markdown": "## Right now, in order\n\n1. **Everyone outside** — people and pets, into fresh air. Don't stop to open windows, don't investigate, don't look for the source.\n2. **Call 911 from outside.** Not from inside the house.\n3. **Tell them if anyone feels unwell.** Headache, dizziness, nausea, confusion — that changes it from an equipment check to a medical call.\n4. **Stay out** until responders confirm it's safe.\n\nThe fire department does not charge for this, and they would far rather check a false alarm than attend the alternative. Carbon monoxide kills hundreds of people in the US each year, and it does it while they sleep.\n\n## 911, the gas utility, or an HVAC tech? Route by symptoms and timing\n\nAll three get called for CO alarms and only one of them belongs in the first five minutes. The deciding factors are whether anyone feels unwell and whether the alarm is sounding right now.\n\n**Anyone has a headache, dizziness, nausea, confusion, or blurred vision** → 911, always, from outside. This is a medical call, not an equipment call. Fire crews carry meters *and* oxygen; utilities carry meters only.\n\n**Alarm is in full alarm pattern (four quick beeps, repeating) and everyone is out and feeling fine** → 911 is still the safe default. If you would rather not tie up an engine and your utility has a 24/7 emergency line, they will also come free and meter the house. Either is correct. What is not correct is waiting until morning.\n\n**Alarm has stopped, nobody feels unwell, and you are already outside** → gas utility emergency line. They will meter, find the appliance producing CO, and shut it off and red-tag it. Free, and they do it at 2am.\n\n**Single chirp every 30 to 60 seconds, no other symptoms** → nobody. That is a low battery or an expired sensor. Replace the battery; if the unit is over 5–10 years old, replace the unit.\n\n**House is cleared and you now need the fault fixed** → HVAC technician, chimney sweep, or plumber, depending on the appliance. This is the only one of the three you pay for, and the only one who actually repairs anything.\n\nThe wrong order is calling your HVAC company first. They will book you for tomorrow, charge a diagnostic fee, and cannot treat anyone. The two organizations that respond in minutes for free are the two you skipped.\n\n## After the emergency: finding the source\n\nOnce the house is cleared, someone has to identify what produced the CO — usually an HVAC technician, though the section below covers the cases where it isn't. The usual suspects:\n\n- **Cracked heat exchanger** in the furnace — the most common, and it means furnace replacement or a significant repair\n- **Blocked flue or chimney** — bird nests, debris, or snow are ordinary causes\n- **Water heater venting** that's disconnected or corroded\n- **Gas range used as a heater** — never do this\n- **Generator or grill** run in a garage, porch, or near an open window\n\nDon't skip this step because the alarm stopped. The alarm stopping means the air cleared, not that the source is gone.\n\n## Nobody who came out will fix it, and the repair trade depends on the appliance\n\nThis catches people out. The fire department meters, ventilates, and leaves. The utility meters, shuts off the offending appliance, hangs a red tag on it, and leaves. Neither repairs anything, and neither is allowed to. The third call is on you, and which trade you want depends on what was producing the CO:\n\n- **Furnace, air handler, or heat pump backup** → HVAC technician.\n- **Chimney, flue liner, fireplace, or wood stove** → a CSIA-certified chimney sweep. Most HVAC companies will decline masonry and liner work outright, which is where people get bounced back and forth.\n- **Gas water heater venting, draft hood, or a disconnected vent connector** → in a lot of jurisdictions this is a plumbing license rather than HVAC. Say \"gas water heater venting\" when you book, not \"CO alarm went off\", and you will get the right van.\n- **Gas range or oven** → appliance repair, not HVAC.\n- **Gas piping or the meter set** → the utility owns everything up to and including the meter; a licensed gas fitter or plumber owns your side of it.\n\nIf the utility red-tagged something, keep the tag and photograph it. It is the document the repair trade needs, and it is also what stops a second contractor from telling you a different story.\n\nGetting bounced between trades at this point is normal rather than bad luck — [the boundaries that cause it, and who takes each job](/home/nobody-will-take-the-job/), covers the common refusals. Whoever ends up taking it is worth [five minutes of checking](/home/vet-a-contractor/) first.\n\n## Before you agree to a new furnace tonight\n\nThe classic CO-alarm upsell is a cracked heat exchanger, quoted at night, with the furnace declared unsafe and a replacement offered on the spot. Sometimes it is entirely true — a cracked exchanger is a genuine reason to condemn a furnace. But it is also the most expensive diagnosis a technician can hand you, and it is very hard for you to verify from the hallway.\n\nThree things to ask for before you sign anything:\n\n1. **Photographs or camera footage of the actual crack**, not a description of one. Every tech doing this work has a phone.\n2. **The combustion analyzer reading in parts per million**, and where in the airstream it was taken. \"It was high\" is not a measurement.\n3. **The red tag**, if the appliance is genuinely unsafe. A utility or a technician condemning an appliance documents it. No paperwork is a signal.\n\nThen sanity-check the number. Fixr puts a full furnace replacement at **$2,800 to $7,500, with a national average of $4,800**. A quote far above that on the night of an alarm, with a discount that expires if you wait, is a sales technique. Unless the unit has been red-tagged and you have no heat in a cold snap, a second opinion in the morning costs you one night and can cost the contractor the job — which is exactly why the pressure exists.\n\nIf you rent, none of this is your bill. Report it in writing, keep the fire department's or utility's paperwork, and let the landlord procure the repair.\n\n## Detector placement, since you're thinking about it\n\nOne on every level of the home, and one outside each sleeping area. CO mixes fairly evenly with air, so height matters less than people think — placement near bedrooms matters most, because that's where the fatal exposures happen. Replace the units themselves every 5–10 years depending on model; the sensors expire even when the battery is fine.",
  "costs": [
    {
      "item": "Furnace heat exchanger replacement",
      "range": "$1,346–$2,673",
      "source": "Fixr",
      "source_url": "https://www.fixr.com/costs/repair-furnace"
    },
    {
      "item": "Full furnace replacement (for sanity-checking a 'condemned furnace' quote)",
      "range": "$2,800–$7,500, national average $4,800",
      "source": "Fixr",
      "source_url": "https://www.fixr.com/costs/furnace"
    }
  ],
  "faq": [
    {
      "q": "Is it just a low battery?",
      "a": "Listen to the pattern. Four quick beeps repeating is an emergency alarm. A single chirp every 30–60 seconds is low battery or end-of-life. If you have any doubt at all, treat it as real and go outside — CO is odorless and colorless, and you cannot check by sniffing."
    },
    {
      "q": "What causes carbon monoxide indoors?",
      "a": "Anything that burns fuel without venting properly: furnaces with cracked heat exchangers, blocked chimneys or flues, gas water heaters, gas ranges used for heating, fireplaces, and — the deadliest — generators or grills run in a garage or near windows. Never run a generator indoors or in an attached garage, ever."
    },
    {
      "q": "What are the symptoms?",
      "a": "Headache, dizziness, weakness, nausea, confusion, blurred vision. It mimics flu without the fever. The tell: symptoms improve when you leave the house and return when you go back, or several people and pets feel ill at once."
    },
    {
      "q": "When can I go back inside?",
      "a": "Only when responders say so after metering the air. They'll also usually identify the source. Don't re-enter to grab things, and don't reset the alarm and assume it was faulty."
    },
    {
      "q": "911 or the gas utility?",
      "a": "If anyone feels unwell, 911 — fire crews carry meters and oxygen, utilities carry meters only. If the alarm is sounding and everyone is out and fine, 911 is still the safe default, though a utility's 24/7 emergency line will also respond free and meter the house. If the alarm has already stopped and nobody has symptoms, the utility is the right call. Both are free, and neither will repair anything — that is a third, paid call."
    },
    {
      "q": "The technician says my heat exchanger is cracked and I need a new furnace tonight. Is that real?",
      "a": "It can be — a cracked heat exchanger is a legitimate reason to condemn a furnace. Verify it before you sign. Ask for photographs or camera footage of the crack, ask for the combustion analyzer reading in parts per million and where it was taken, and ask for the red tag if the appliance is genuinely unsafe. Then check the number: Fixr puts full furnace replacement at $2,800 to $7,500, national average $4,800. Unless the unit is red-tagged and you have no heat in freezing weather, a second opinion in the morning is worth the night."
    }
  ],
  "sources": [
    {
      "label": "Fixr: Furnace repair cost",
      "url": "https://www.fixr.com/costs/repair-furnace",
      "accessed": "2026-08-11"
    },
    {
      "label": "Fixr: Furnace replacement cost",
      "url": "https://www.fixr.com/costs/furnace",
      "accessed": "2026-08-10"
    },
    {
      "label": "US Fire Administration: Home fire prevention",
      "url": "https://www.usfa.fema.gov/prevention/home-fires/",
      "accessed": "2026-08-09"
    }
  ],
  "updated": "2026-08-24",
  "url": "https://whodoicallfor.com/gas/co-alarm-going-off/",
  "json_url": "https://whodoicallfor.com/gas/co-alarm-going-off.json",
  "recommended_call": null
}