1. Do NOT silence and ignore it
2. Get everyone (including pets) out of the house immediately
3. Leave the door open as you exit
4. Call 911 from outside or a neighbor's house
5. Do NOT re-enter until cleared by emergency responders
Carbon Monoxide Safety for Minnesota Homeowners
Carbon monoxide poisoning kills approximately 400 Americans annually and hospitalizes 50,000 more — with the highest rates occurring in cold-climate states where homes are tightly sealed in winter and gas furnaces run continuously for months. Understanding CO risks, symptoms, and prevention is essential for Minnesota homeowners.
How Furnaces Produce Carbon Monoxide
Natural gas furnaces burn fuel to produce heat. When combustion is complete (the way it should work), the byproduct is primarily CO₂ (carbon dioxide) and water vapor — harmless in small amounts. But incomplete combustion produces CO (carbon monoxide) — colorless, odorless, and deadly.
The most common furnace-related CO causes:
- Cracked heat exchanger: The #1 cause — a crack allows combustion gases to mix with circulating air. This is a replacement situation, not a repair.
- Blocked flue or exhaust vent: Prevents combustion gases from venting properly — common after heavy snow or bird/rodent nesting in vents
- Oversized furnace: Short-cycling from an oversized unit creates incomplete combustion
- Improper maintenance: Dirty burners or restricted airflow leads to incomplete combustion
- Back-drafting: Exhaust pulled back into the home by negative pressure (common when running exhaust fans with older furnaces)
CO Symptoms: Know Them
| CO Level (PPM) | Symptoms | Time to Incapacitation |
|---|---|---|
| 35 ppm | Headache after 6–8 hours | Hours |
| 200 ppm | Headache, dizziness, disorientation in 2–3 hours | 2–3 hours |
| 400 ppm | Frontal headache in 1–2 hours; life-threatening in 3 hours | 3 hours |
| 1,600 ppm | Headache, dizziness, nausea in 20 minutes | 1 hour |
CO Detector Requirements in Minnesota
Minnesota state law (Minn. Stat. §299F.50) requires carbon monoxide alarms in all dwellings that have fossil fuel-burning equipment or an attached garage. Requirements:
- CO alarms must be installed within 10 feet of each sleeping room
- Required when selling or transferring property (must be installed and functioning)
- Combination smoke/CO detectors satisfy the requirement
- CO alarms have a typical lifespan of 5–7 years — check the manufacture date on yours
Furnace Maintenance to Prevent CO Risk
- Annual professional tune-up: Includes heat exchanger inspection — the single most important CO-prevention maintenance item
- Check exterior vents after snowstorms: Blocked PVC vents on high-efficiency furnaces are a leading cause of CO buildup in Minnesota winters
- Keep gas appliances serviced: Water heater, fireplace, and dryer vents also need regular inspection
- Never run cars in attached garages: Even briefly — CO seeps through any gap into the living space
- Replace aging furnaces proactively: Furnaces over 15–20 years old have higher heat exchanger crack rates. Use our Model Lookup Tool to check your furnace's age.
If Your HVAC Tech Finds a Cracked Heat Exchanger
A cracked heat exchanger is not a repair situation — it requires full furnace replacement. A crack allows combustion gases (including CO) to mix directly with the heated air circulating through your home. Do not operate a furnace with a confirmed cracked heat exchanger.
Furnace Direct can have a replacement unit delivered same-day to the Twin Cities area. Call (888) 762-1334 immediately if your tech has found a crack.
🔥 Ready to Replace Your Furnace?
Get a same-day quote from Furnace Direct — factory-direct pricing, no middlemen.
CO Safety FAQs
Get wholesale pricing on a new system.
Tell us a little about your home and what you're replacing. We'll send real numbers on a Goodman 96% AFUE setup — shipped direct to your door anywhere in the lower 48. No contractor markup, no obligation.