Carbon Monoxide Safety in Winter: Furnaces, Fireplaces, Generators and CO Alarms

What it is: A practical winter CO safety guide for North American homes.
Core function: Explains how fuel-burning equipment can create CO risk and how a CO alarm adds a warning layer.
Who it is for: Homeowners, renters, families using furnaces, fireplaces, generators, or other fuel-burning equipment.

Why Does CO Risk Matter More During Cold Weather?

Cold weather changes how people use their homes.

Families may:

· Run furnaces longer

· Use fireplaces

· Use gas heaters

· Operate generators during power outages

· Keep windows closed

· Spend more time indoors

These conditions can increase the importance of CO awareness.

The CPSC issued winter safety guidance in January 2026 specifically warning about CO poisoning associated with heating equipment, generators, furnaces, and fireplaces.

Furnaces and Heating Systems

A furnace or other fuel-burning heating appliance can produce CO when combustion or venting is not working correctly.

Potential problems include:

· Vent obstruction

· Loose connections

· Improper combustion

· Backdrafting

· Negative pressure

· Poor maintenance

· Improper installation

Excessive spillage or reverse venting, negative pressure caused by exhaust fans, competing fuel-burning appliances, loose vent connections, and vent obstructions among potential causes of transient CO conditions.

This is why a CO alarm should not be considered a replacement for professional appliance maintenance.

Fireplaces

Fireplaces can also produce CO.

Important safety practices include:

· Ensure the chimney and venting system are properly maintained.

· Follow the appliance manufacturer's operating requirements.

· Make sure the fireplace damper is properly positioned.

· Never burn inappropriate materials.

· Keep CO alarms operational.

CPSC advises homeowners to have heating systems, chimneys, and vents inspected and serviced annually by a trained technician.

Portable Generators

Generators deserve special attention.

A portable generator produces engine exhaust containing CO.

CPSC guidance states that generators should be used outdoors and at least 20 feet from the home, with exhaust directed away from the house.

The CDC similarly warns that generators, grills, camp stoves, and other fuel-burning equipment should never be used inside homes, basements, garages, campers, or near openings such as windows.

A CO alarm is an additional protection layer.

It is not permission to use a generator indoors.

Never Run a Vehicle in an Attached Garage

Even with the garage door open, running a vehicle in an attached garage can allow CO to enter the home.

The CPSC specifically warns against leaving a vehicle running in an attached garage, even when the garage door is open.

The motor vehicles operating in an attached garage or near a residence as a potential CO source.

What Does a CO Alarm Add?

A CO alarm provides an independent warning when dangerous CO conditions are detected.

HM-735ESY provides:

· CO detection

· Audible alarm

· Red/yellow/green status indication

· LCD concentration display

· Alarm memory

· Early warning

· Test/Hush function

· Low-battery warning

· End-of-life warning

Winter CO Safety Checklist

Before winter

· Have heating equipment inspected.

· Check chimneys and vents.

· Confirm CO alarms are operational.

· Test each alarm.

· Replace batteries when required.

· Check alarm age.

· Review the household emergency plan.

During a power outage

· Never operate a portable generator indoors.

· Keep generators at least 20 feet from the home.

· Point exhaust away from the house.

· Never use charcoal indoors.

· Never use a gas oven to heat the home.

· Make sure CO alarms are working.

CPSC's winter guidance emphasizes these practices.

HM-735ESY Winter-Relevant Specifications

Why Is Generator CO Particularly Dangerous?

Generator-related CO can develop rapidly.

Unlike a slowly developing household issue, an improperly positioned generator can produce substantial exhaust close to an occupied building.

The CDC notes that during power outages, alternative sources of fuel or electricity can cause CO to build up in homes, garages, and campers.

People may also be:

· Sleeping

· Distracted

· Focused on restoring power

· Unaware of the exhaust

· Unable to smell CO

This makes a working CO alarm especially important during emergency situations.

What Symptoms Should Families Know?

The CDC lists common symptoms including:

· Headache

· Dizziness

· Weakness

· Upset stomach

· Vomiting

· Chest pain

· Confusion

The HM-735ESY safety information also describes mild, medium, and extreme exposure symptoms, ranging from headache and nausea to confusion, unconsciousness, convulsions, and cardiopulmonary failure.

If CO poisoning is suspected, do not attempt to diagnose yourself at home.

Get outside and seek emergency medical assistance.

What Should You Do If the Alarm Sounds During a Power Outage?

The same basic rule applies:

Leave the area and get to fresh air.

Do not:

· Disable the alarm

· Remove its batteries

· Assume the generator is too far away

· Assume the windows are open enough

· Wait for symptoms

· Re-enter simply because the alarm stops

Winter Maintenance for HM-735ESY

recommends:

· Weekly testing

· Annual cleaning using compressed air or a vacuum hose

· No water or cleaning solvents

· Immediate replacement if the alarm cannot be cleaned adequately

· Immediate battery replacement after a low-battery warning

Final Takeaway

Winter CO safety is not about one device.

It is a system of behaviors:

· Maintain heating equipment.

· Maintain chimneys and vents.

· Use generators outdoors and safely away from the home.

· Never run vehicles in attached garages.

· Install CO alarms appropriately.

· Test alarms regularly.

· Replace batteries when required.

· Replace alarms at end of life.

· Know what to do when an alarm sounds.

A CO alarm adds an important warning layer, but safe fuel-burning equipment operation remains essential.