What are signs of carbon monoxide on a furnace?

Author: Lenny Schneider MD  |  Last update: Sunday, June 8, 2025

Heavy condensation on the windows (found in the room with your furnace) Yellow or brown soot-like stains found around your furnace. A yellow pilot light (instead of a blue flame) Stuffy indoor air.

How do I know if my furnace is giving off carbon monoxide?

Signs of a Furnace Carbon Monoxide Leak

These signs may include frequent pilot light blow-outs, soot accumulation in the fireplaces, smears of yellow/brown stains near appliances, duller than normal flames from their fires as well as noticeable smells like stale air and burning.

What are two warning signs of carbon monoxide poisoning?

The most common symptoms of CO poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. CO symptoms are often described as “flu-like.” If you breathe in a lot of CO, it can make you pass out or kill you.

What are the symptoms of carbon monoxide poisoning from a heater?

Key points about carbon monoxide poisoning

A common source is unvented space heaters. Symptoms of CO poisoning include headache, dizziness, weakness, nausea and vomiting, rapid heartbeat, shortness of breath, seizures, chest pain, disorientation, and loss of consciousness.

How do you test a furnace for carbon monoxide?

According to the CDC, carbon monoxide is a silent killer that takes hundreds of lives per year. Unfortunately, you cannot tell just by looking at your furnace whether it is leaking carbon monoxide. You need a carbon monoxide detector or other special equipment to test the levels yourself.

SYMPTOMS AND CAUSES OF CARBON MONOXIDE POISONING - PLUS HOW TO PREVENT IT

How can you detect carbon monoxide without a detector?

Since carbon monoxide is odorless and colorless, a detector is the only reliable way to identify its presence. However, signs like soot buildup near appliances, pilot lights frequently going out, stale air, or excessive condensation on windows could indicate a potential issue.

Do all furnaces give off carbon monoxide?

Any furnace that burns fuel produces carbon monoxide as a byproduct. This is the same for any appliance in your home that burns fuel, such as a gas range. Therefore, if your furnace uses natural gas, propane, or oil to make heat, your furnace creates carbon monoxide. Electric furnaces do not create carbon monoxide.

Will opening a window help with carbon monoxide?

If you experience symptoms that you think could be from CO poisoning: DO GET FRESH AIR IMMEDIATELY. Open doors and windows, turn off combustion appliances and leave the house.

How to tell if carbon monoxide is in the air?

The best way to alert you and your family to unsafe levels of CO is to install a carbon monoxide detector. It works like a smoke alarm, sampling the air in your home and creating a loud alarm when levels of the gas are detected. It's important to evacuate your home immediately when your CO alarm sounds.

Which heaters leak carbon monoxide?

Carbon Monoxide and Water Heaters

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that can be deadly if inhaled in large amounts. While it is commonly associated with gas water heaters, it is possible for electric water heaters to leak carbon monoxide as well.

How to detect carbon monoxide with iPhone?

Go to the Home app on your iPhone or iPad. , then tap Home Settings. Tap Safety & Security. Tap Sound Recognition, then turn on Smoke & CO Alarm.

How to clear carbon monoxide from a house?

If no one is feeling symptoms, ventilate the home with fresh air and turn off all potential sources of CO. That includes your oil or gas furnace, gas water heater, gas range and oven, gas dryer, gas or kerosene space heater, and any vehicle or small engine.

Do smoke detectors detect carbon monoxide?

But even though you have a comprehensive smoke detection system, it isn't enough to protect against the threat of carbon monoxide. Carbon monoxide is an odorless, tasteless, and invisible gas that can make inhabitants sick or even lead to death.

How do I know if my house is full of carbon monoxide?

Carbon monoxide is invisible, odorless and tasteless. Inspection helps protect yourself and your family. Install a carbon monoxide detector in your house, and plan to check its battery every time you check your smoke detector batteries.

How to tell if a furnace is leaking gas?

If you detect any of the following signs of a natural gas leak in your house or think you have been exposed, contact 911 immediately.
  1. The smell of rotten eggs. In its natural state, natural gas is odorless and colorless. ...
  2. Hissing sounds. ...
  3. Air bubbles outside your home. ...
  4. Dead or dying plants. ...
  5. Higher-than-normal gas usage.

Will turning off the gas stop carbon monoxide?

If your boiler is switched off at the mains, your boiler will not be burning fuel and therefore no waste carbon monoxide gas will be produced.

How can you tell if your furnace is leaking carbon monoxide?

Warning Signs of a Furnace CO Leak
  • Heavy condensation on the windows (found in the room with your furnace)
  • Yellow or brown soot-like stains found around your furnace.
  • A yellow pilot light (instead of a blue flame)
  • Stuffy indoor air.
  • The smell of gas/burning.
  • The pilot light constantly blows out.
  • Rust found on the vent pipe.

How to tell if there's carbon monoxide without a detector?

Signs of a carbon monoxide leak in your house or home

Sooty or brownish-yellow stains around the leaking appliance. Stale, stuffy, or smelly air, like the smell of something burning or overheating. Soot, smoke, fumes, or back-draft in the house from a chimney, fireplace, or other fuel burning equipment.

What is the easiest way to detect carbon monoxide?

A portable CO detector can be useful for detecting carbon monoxide levels near all gas-powered appliances. It's a handy way to check every room of the house. These units can be hardwired with battery backup, or you can choose a battery powered model.

What puts off carbon monoxide in a house?

The most common causes of carbon monoxide building up are incorrectly installed or poorly maintained or ventilated appliances – like stoves and hot water heaters. Poorly ventilated fireplaces and other gas- or wood-burning appliances can also pose danger.

Can dogs smell carbon monoxide?

Carbon monoxide, commonly known as CO, is an odorless, colorless, and non-irritating gas. No pet can identify the gas because CO lacks any scent whatsoever. Exposure can lead to carbon monoxide poisoning in both humans and pets.

How to check for CO2 in house?

In order to measure CO2 levels in your home, you will need a carbon dioxide monitor or tester. With a CO2 tester you can easily and affordably measure carbon dioxide levels in your home. These devices come in several different types including handheld, desktop, or wall-mounted units.

How long does it take for carbon monoxide to build up in a house?

Small carbon monoxide leaks can fill every room in your house with poisonous gas within eight hours. Severe leaks can cause this problem in just five minutes. The EPA states that exposure to concentrations of nine ppm or more for eight hours is enough to produce harmful health effects for at-risk individuals.

Should I put a carbon monoxide detector next to the furnace?

Yes, it's recommended to place a carbon monoxide detector at least 15 feet away from furnaces to avoid nuisance alarms. Furnaces can be a common source of carbon monoxide leaks.

Can a dirty furnace filter cause carbon monoxide?

A furnace running with a clogged air filter is starved for ventilation and produces high levels of carbon monoxide (CO) – a colorless, odorless gas than can be fatal for humans and their pets. A clogged air filter can also increase the chances of a fire, further advancing the safety concerns in this home.

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