“It turns on” answers only one question
During a showing or walkthrough, it is easy to raise the thermostat, feel warm air, and move on. That check confirms the equipment responded at that moment. It does not establish that combustion is correct, exhaust is leaving the building, the vent remains intact, required air is available, the system is maintained, or the carbon-monoxide alarms are placed and functioning as intended.
Carbon monoxide—CO—is colorless and odorless. The U.S. Consumer Product Safety Commission and CDC identify furnaces, water heaters, fireplaces, generators, vehicles, grills, and other fuel-burning equipment as potential sources when fuel burns incompletely or exhaust accumulates. Natural-gas odor and carbon monoxide are different hazards: a person cannot rely on smell to detect CO.
Northern Utah’s cold weather adds practical pressure. Heating equipment runs longer, homes stay closed, snow can obstruct exterior terminations, fireplaces return to service, and power outages can tempt unsafe generator use. The Utah State Fire Marshal advises annual professional inspection of fuel-burning equipment and chimneys, clear exterior vents, and maintained CO alarms.
1. Inventory every source—not only the furnace
Start with a room-by-room and exterior inventory. Include the furnace or boiler, water heater, fireplace, wood or pellet stove, gas range, gas dryer, garage heater, shop heater, decorative appliance, standby or portable generator, and any fuel-burning equipment in an accessory building. Note the fuel, model, serial number, approximate installation date, vent type, service provider, and permit or warranty records.
Also map attached or enclosed spaces that can introduce exhaust: garages, workshops, mechanical closets, crawlspaces, attics, basement rooms, and additions. Ask whether a remodel changed a door, wall, return-air path, chase, chimney, roofline, or exterior termination near an appliance.
A home may have several independent systems. A recently replaced furnace does not answer questions about an older atmospheric water heater sharing a room or flue. An electric heat pump does not eliminate the need to review a gas fireplace, range, or attached garage.
Illustrative example
A buyer sees a high-efficiency furnace installed two years ago and assumes the combustion question is finished. The mechanical room also contains an older water heater with a separate metal vent. A finished basement project added a door and storage around the room. The right review separates the new furnace from the water heater, combustion-air openings, room configuration, vent connection, permits, and alarm placement instead of treating “new furnace” as a system-wide conclusion.
2. Read the service record for what it actually covers
Request installation invoices, permits, inspection approvals, manufacturer documents, service tickets, filter history, chimney or flue records, repairs, alarm replacement dates, and any utility or fire-department response. Match the company name and equipment model across the records.
A generic “HVAC serviced” receipt may not say which appliance was examined or what was measured. Ask the service provider to identify the equipment and inspection scope in writing. Depending on the system, a qualified professional may evaluate combustion performance, safety controls, heat exchanger condition, gas pressure, vent draft, flue integrity, condensate management, electrical connections, and manufacturer-required maintenance.
CPSC recommends annual professional inspection and service of the heating system, including checks for chimney and flue blockages, corrosion, disconnections, and loose connections. CDC similarly advises annual service of heating systems, water heaters, and other gas-, oil-, or coal-burning appliances by a qualified technician.
Do not treat a home inspection as a substitute for specialized service when the inspector recommends further evaluation or cannot access part of the system. The useful question is not whether somebody “looked at the furnace,” but what equipment and safety functions were actually evaluated.
3. Follow air into the appliance and exhaust out
Fuel-burning equipment needs the air and venting required by its design and installation. A qualified professional should evaluate the full path rather than only the visible appliance cabinet.
Look for questions such as:
- Where does the appliance receive combustion air?
- Has a door, wall, insulation project, storage area, or remodel changed that air supply?
- Is the vent correctly sized, supported, joined, sloped, and routed for the connected equipment?
- Does more than one appliance share a chimney or vent?
- Are there signs of corrosion, staining, heat damage, condensation, disconnected sections, or makeshift repairs?
- Are exterior intake and exhaust terminations clear of snow, vegetation, nests, covers, stored items, and construction debris?
- Could exhaust be drawn toward a nearby window, door, soffit, air intake, or enclosed area?
- Does the fireplace damper, chimney, liner, and cap fit the fuel and intended use?
These observations are prompts for professional review, not a homeowner diagnosis. Venting systems vary. Do not disassemble, adjust, relight, or service fuel-burning equipment unless the manufacturer and your qualifications support the work.
Dominion Energy’s current safety guidance warns that blocked exhaust vents or combustion-air ducts can expose occupants to carbon monoxide. It also advises keeping snow and ice away from gas meters and appliance vents and having furnaces or boilers inspected annually by a qualified heating contractor.
4. Separate carbon-monoxide alarms from equipment condition
A CO alarm is a critical warning device, not proof that the furnace or vent is safe. CPSC explicitly says alarms add protection but do not replace correct installation, use, and maintenance of fuel-burning appliances.
CPSC and the Utah State Fire Marshal recommend CO alarms on every level of the home and outside sleeping areas. Interconnected alarms provide broader warning because activation of one causes the others to sound. Follow the alarm manufacturer’s placement, mounting, testing, battery, and replacement instructions; avoid inventing a universal mounting height or life span when the specific product controls.
Create an alarm schedule with:
- location and level of the home;
- manufacturer and model;
- manufacture or installation date;
- power source and battery type;
- test date and test result;
- end-of-life signal or replacement date; and
- whether alarms are interconnected.
The test button generally confirms the alarm’s circuitry, not the accuracy of its CO sensor. Replace alarms according to the manufacturer’s instructions and end-of-life signal. Do not cover them with furniture, draperies, paint, or renovation dust.
Smoke alarms and CO alarms address different hazards. A combination unit may perform both functions if listed and installed for them, but a smoke alarm alone does not detect carbon monoxide.
5. Know the difference between an alarm, symptoms, and a gas odor
Make the response plan simple enough to follow under stress.
If a CO alarm sounds: CPSC advises moving everyone outside to fresh air immediately, calling 911 or the fire department from outside, accounting for all occupants, and staying out until emergency responders say reentry is safe. Do not search the house for the source. Do not restart equipment identified as a possible source until trained personnel have serviced it.
If people have possible CO symptoms: headache, dizziness, weakness, nausea, chest pain, and confusion can resemble other illnesses. CDC says high exposure can cause unconsciousness and death, and sleeping people may not recognize symptoms. Leave for fresh air and seek emergency help; tell responders or medical professionals that CO exposure is suspected.
If there is a strong natural-gas odor: follow the serving utility’s emergency directions. Dominion Energy advises leaving the building, avoiding switches, phones, flames, vehicles, or other possible ignition sources near the suspected leak, and contacting the utility from a safe location. Do not attempt to find the leak yourself.
The plan should identify the gas utility, electric utility, fire department, qualified service company, equipment shutoff locations, and household meeting point. Emergency instructions belong where every occupant can find them—not only in the owner’s phone.
6. Treat the garage as part of the air-safety review
Never run a vehicle or fuel-powered engine in an attached garage, even with the garage door open. CPSC and CDC both warn that carbon monoxide can accumulate and enter the home. The same rule applies to generators, pressure washers, and other engines.
For due diligence, examine the door between the garage and living area, walls and ceilings shared with the home, penetrations, weatherstripping, return-air locations, and any room above or beside the garage. Have the appropriate inspector or contractor evaluate defects and code questions. Do not describe a garage as “sealed” based on appearance alone.
Ask about recurring remote-start use, workshop equipment, garage heaters, and storage that blocks vents or appliance clearances. A garage conversion or addition deserves extra scrutiny because it may have changed both the building enclosure and mechanical system.
7. Plan for power outages without moving exhaust indoors
A portable generator belongs outdoors—never in a home, basement, garage, shed, or near openings. CDC recommends operating generators more than 20 feet from windows, doors, and vents. CPSC similarly advises at least 20 feet with exhaust directed away from the home. Opening garage doors or windows does not make indoor generator operation safe.
Before buying or selling a home with generator equipment, document:
- whether the unit is portable or permanently installed;
- manufacturer instructions and intended placement;
- fuel type and safe fuel storage;
- transfer equipment and electrical permits;
- service and exercise records for standby equipment;
- location relative to openings and neighboring buildings; and
- the CO-alarm plan during use.
Have qualified electrical, fuel-gas, building, and equipment professionals review permanent installations. A cord through a window or an improvised connection is not a safe backup-power plan.
8. Include fireplaces, chimneys, and space heaters
Fireplaces and solid-fuel appliances bring both fire and carbon-monoxide questions. CPSC recommends annual professional inspection of fuel-burning heating systems, fireplaces, chimneys, flues, and vents. The Utah State Fire Marshal also advises annual cleaning and inspection by a qualified professional.
Ask what fuel the appliance is designed to use, whether the chimney or liner matches it, when it was last inspected or cleaned, and whether repairs were documented. Open the damper as directed before lighting a fire and follow the manufacturer’s operation instructions. Do not assume a decorative fireplace is approved as a primary heat source.
Keep portable heaters away from combustible materials and follow the device instructions. The Utah State Fire Marshal recommends at least three feet between space heaters and items that can burn. Never use an oven or range to heat the home, and never bring charcoal grills or outdoor fuel-burning equipment inside.
9. For buyers: make the inspection window large enough
Order the general home inspection early enough to schedule specialized HVAC, plumbing, chimney, fireplace, gas, or electrical evaluation if needed. Request access to mechanical rooms, attic or crawlspace vent routes, exterior terminations, alarm locations, and service records.
Questions worth resolving before the deadline include:
- Which appliances burn fuel and which are electric?
- What equipment was installed or altered, by whom, and under what permit?
- What did the last professional service include?
- Are any vent sections concealed or inaccessible?
- Did a basement finish, addition, air-sealing project, or roof replacement affect the system?
- Are alarm locations, ages, power sources, and interconnection documented?
- What open repairs, service recommendations, or jurisdictional corrections remain?
A seller’s maintenance record is useful, but it is not a warranty of future performance. A buyer’s goal is a property-specific evaluation and an understandable plan for unresolved items.
10. For sellers and new-construction buyers: demand a clean handoff
Sellers can gather equipment schedules, service invoices, permits, alarm records, chimney reports, manuals, warranties, and repair documentation before listing. Describe facts accurately without calling a system “safe,” “to code,” or “maintenance-free” unless the responsible qualified professional provides that conclusion.
New-construction buyers should review the mechanical plans and final installation as separate checkpoints. Confirm equipment models, intake and exhaust locations, required clearances, condensate routing, thermostat and control setup, alarm locations and interconnection, startup or commissioning records, permits, inspections, manuals, filters, warranty registration, and service contacts.
Before final walkthrough, make sure exterior vents are not blocked by construction materials, landscaping, snow, or temporary covers. Ask the builder to explain which maintenance tasks belong to the owner and which conditions require professional service. Connect this handoff to the new-construction walkthrough guide and the construction closeout guide.
A winter combustion-safety file
- Inventory: List every fuel-burning appliance, fireplace, heater, generator, and attached engine space.
- Records: Match models to permits, installation invoices, service history, manuals, and warranties.
- Air and venting: Have qualified professionals evaluate combustion air, chimneys, flues, joints, and exterior terminations.
- Alarms: Record locations, models, dates, power sources, interconnection, tests, and replacement instructions.
- Emergencies: Post the outside evacuation point and numbers for 911, the gas utility, and qualified service providers.
- Handoff: Keep the file with the home so the next occupant does not have to reconstruct the system.
The goal is not to make buyers afraid of fuel-burning equipment. It is to stop using warmth, appearance, or the absence of an odor as proof that the complete system is understood. Good due diligence connects the appliance to its air, vent, warning devices, records, and response plan.
Sources and further guidance
Review the U.S. Consumer Product Safety Commission’s carbon-monoxide fact sheet and family safety guidance, the CDC’s CO prevention guidance, the Utah State Fire Marshal’s home fire and CO safety page, and Dominion Energy’s natural-gas safety guidance. This article is general educational information, not individualized medical, mechanical, engineering, code, insurance, legal, lending, tax, or financial advice. Follow emergency directions, manufacturer instructions, the serving utility, the authority having jurisdiction, and qualified professionals for the exact property.