Carbon monoxide investigation: what it is and when you need it
Updated Sep 2026·National·Diagnostics & problems
What is a carbon monoxide investigation?
A carbon monoxide investigation checks the venting of every fuel-burning appliance after an alarm has sounded or symptoms point at carbon monoxide. The technician looks for spillage at the draft hood, blockage, an undersized or shared flue, and back-drafting pulled on by exhaust fans.
The work overlaps with the heating trade, and a fault inside a gas appliance belongs to whoever is licensed for it where you live.
When is it actually needed?
Immediately after a carbon monoxide alarm, and whenever headaches, nausea or window condensation follow the heating coming on. Leave the building first and call the fire department or the gas utility.
What standard does it answer to?
NATIONAL · NFPA 211NATIONAL · IRC
- NFPA 211, the Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances — the national standard that sets the yearly inspection and the three inspection levels.
- The International Residential Code (IRC) — the model building code for one- and two-family homes, adopted and often amended state by state and city by city.
What should the invoice or report show?
Ask for the readings taken, where they were taken, and with what instrument.
What does it cost?
Quote after inspection. We have no researched national range for a carbon monoxide investigation, so expect a written quote once someone has looked at the job — with the work named on its own line.
Does your state regulate this?
VARIES BY STATE
NFPA 211 and the IRC are national model documents, not state law: which edition applies to your home, if any, depends on the codes your state and city have adopted. Licensing, permits and what is allowed for a carbon monoxide investigation differ by state, and sometimes by city. A fault inside a gas appliance belongs to whoever is licensed for gas work where you live — a gas fitter, a plumber or a licensed heating contractor, depending on the state. Our 50-state laws table and licensing by state set out what each state requires.
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Questions about a carbon monoxide investigation
When is a carbon monoxide investigation needed?
Immediately after a carbon monoxide alarm, and whenever headaches, nausea or window condensation follow the heating coming on. Leave the building first and call the fire department or the gas utility. The work answers to NFPA 211 and the IRC.
Is a carbon monoxide investigation regulated by state law?
NFPA 211 and the IRC are national model documents, not state law: which edition applies to your home, if any, depends on the codes your state and city have adopted. Licensing, permits and what is allowed for a carbon monoxide investigation differ by state, and sometimes by city. A fault inside a gas appliance belongs to whoever is licensed for gas work where you live — a gas fitter, a plumber or a licensed heating contractor, depending on the state. Our 50-state laws table and licensing by state set out what each state requires.
What should I ask before agreeing to a carbon monoxide investigation?
Ask for the readings taken, where they were taken, and with what instrument.