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CO present

What is going on

Possible causes and checks for: co present.

Likely causes

  • Cracked heat exchanger
  • Poor venting/chimney
  • Unvented gas appliance
  • Vehicle in attached garage
  • Negative pressure backdraft

Check in this order

  1. Repair/vent appliance
  2. No engines in garage
  3. CO detector
  4. Dedicated combustion air

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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.