The Best Carbon Monoxide Detector (Expert Answers)

Carbon Monoxide Detector, Low Level CO Detector -

The Best Carbon Monoxide Detector (Expert Answers)

Carbon Monoxide is a deadly gas that must be taken serious. It is the "silent killer" because it is colorless, odorless and tasteless. This is the exact reason why so many states and cities have mandated carbon monoxide detectors in the home. CO alarms are crucial for home safety and also important when traveling, RV driving and boating.



  • Carbon Monoxide detectors help protect from unintentional CO exposure.
  • CO alarms are affordable.
  • A plethora of Carbon Monoxide Detectors and Meters exist for a variety of applications.
  • Carbon Monoxide symptoms may be passed as "flu like"
  • Sometimes it is difficult to track down the culprit carbon monoxide source.
  • Carbon Monoxide poisoning public awareness is still limited.
  • Carbon Monoxide is a silent killer.

What is Carbon Monoxide?

Carbon monoxide is a toxic gas. OSHA emphasizes that carbon monoxide (CO) is a poisonous, colorless, odorless and tasteless gas - making it very elusive. Although CO has no odor, it is often mixed with other gases that do have an odor (i.e. exhaust gas).

When carbon monoxide is inhaled, your body replaces the oxygen in your red blood cells with carbon monoxide. This leads to asphyxiation, serious tissue damage, brain damage and even death.

Is Carbon Monoxide Dangerous? 

Based on the CDC, about 430 people die in the USA from unintentional or accidental CO poisoning. Approximately 50,000 Americans visit the emergency room yearly due to unintentional CO poisoning. 

What are Carbon Monoxide Symptoms?

CO is particularly dangerous when sleeping and often poisoning occurs during the night periods. People may have irreversible brain damage or may die before anyone realizes there is a problem hence it is called the silent killer. The Mayo Clinic mentions that typical signs and symptoms of carbon monoxide exposure and poisoning include:

  • Headache
  • Weakness
  • Dizziness
  • Nausea or vomiting
  • Shortness of breath
  • Confusion
  • Loss of consciousness

What Produces Carbon Monoxide?

The Cleveland Clinic mentions that CO is found in exhaust and flue gases produced during any form of combustion. Common examples and problem situations include:

  • Car and truck engines (leaving a car running in the garage).
  • Small gasoline engines (portable generators running in or close to the home).
  • Gas stoves and Gas Lanterns (using your home oven for heating).
  • Heating systems, including home furnaces (cracked heat exchangers and backdrafting effects).
  • Burning charcoal, kerosene, propane or wood (indoor BBQ).
  • Tools with small engines such as saws (used in confined spaces is deadly)

What Shall I do if I Suspect Carbon Monoxide is in my Home?

If you suspect you may be experiencing carbon monoxide poisoning symptoms immediately seek fresh outdoor air. Evacuate from your indoor surroundings and call 911.

If someone is unable to leave the building, or is unconscious, open doors and windows to the outside in the area the person is located, but do so without causing yourself harm. Dont forget, CO is odorless and tasteless. Evacuate fast.  First responders have CO meters and can enter an indoor space in a safe manner.

The fire department may be able to find the source of elevated carbon monoxide and provide you with feedback and guidance on the actual CO problem area. If it is a defective appliance, ensure it is inspected by a qualified professional, have the appliance repaired, or better yet, replaced.

Beaware if you are living in a building with other occupants. The CO may be coming from your neighbor. CO movement is elusive, there may be turbulence effects, micro plume effects and drafts that is hard to imagine and hence, CO may be sourced in one location, but may shuttle to a totally different area.

fire department carbon monoxide

What if I inhaled CO gas?

If you think you're suffering from CO exposure, breathe some fresh air as soon as you can. Move to an outdoor fresh air environment. 

Call the fire department or paramedic to be on the safe side. Seek medical help, you may require oxygen. You may require to be tested so medical professionals get a better insight into your exposure severity. Based on the data and diagnosis, you may require hyperbaric therapy.

Tips to Prevent a Carbon Monoxide leak? 

There are many things you can do to remain safe throughout the year from carbon monoxide. First and foremost, understand all combustion appliances that exist in and around your home. You would be surprised how many home owners and tenants simply do not know the location of their gas burning appliances. Such awareness is imperative for your safety.

  • Make it a habitual task to visual inspect your gas burning appliance flue stacks, make sure everything is in order.
  • If you are living in a shared building, ask your landlord, understand the location of all gas burning appliances - most dangerous are pool heaters as they have a massive BTU rating, and hence emit large volumes of exhaust gas.
  • Have a professional install your appliances such as heating equipment, water heaters or central heating equipment. 
  • Keep vents and exhausts clear of blockages or obstructions. Again, understand your venting situation, know what is intake and what is an exhaust.
  • Change your CO detector batteries once per year.
  • Do not use an oven or range stovetop to provide heat to your home.
  • Reduce use of portable or space heaters. Turn them off when sleeping. Ensure good airflow and ventilation in your indoor space.
  • Install carbon monoxide detectors on each floor of your home and within 15 feet of each sleeping area.
  • CO detectors have a limited life span; check the manufacturer's instructions for information on replacement. Typical lifespan of a CO detector is from 2 to 10 years.
  • Never leave your car running your garage. If you are forgetful or have dementia, refrain from parking in your garage.
  • Never use portable generators inside homes or garages, even if doors and windows are open. Keep generator exhaust position down wind and away from your home.
  • Never BBQ into the house or garage. Propane grills are also dangerous for heating or cooking. Do not BBQ in the garage.

Do I Need a CO Detector?

Yes! They are cheap and there are no excuses!

Do yourself and your family a favor. Be safe and be smart.

It actually may be mandatory that you have one in your home by your local city code and/or state legislation. The majority of US state have now mandated CO detectors in dwellings. 

Where Should a CO Detector be Placed?

CO alarms should be mounted in or near bedrooms and living areas. It is recommended that you install the CO alarm (at minimum) on each level of your home. 

For best protection, we recommend installing a CO detector in each bedroom (since most CO related deaths occur when sleeping), living areas, garage or basement (for very early warning accumulation).

When choosing your installation locations, make sure you can hear the alarm from all sleeping areas. If you install only one CO alarm in your home, install it near bedrooms. When wall mounting, keep it out of the reach of children, pets or accidental bumps.

Placing the alarm at eye level is recommended as it allows for optimum daily monitoring of the digital display.

It is also a good idea to think about the places you should avoid, these areas include: 

  • Do not install in areas where the temperature is colder than 40°F (4.4°C) or hotter than 100°F (37.8°C), it will stress the CO sensor and may reduce its useful life.
  • Do not install within 5 feet of heating or cooking appliances.
  • Do not install near vents, flues, chimneys or any forced/unforced air ventilation openings.
  • Do not install near ceiling fans, doors, windows or areas directly exposed to the weather so external air, water or rain reaches the alarm.
  • Do not install in dead air spaces, such as peaks of vaulted ceilings or gabled roofs, where CO may not reach the sensor in time to provide early warning.
  • Do not install on a switched or dimmer-controlled outlet.
  • Do not install this unit near deep-cell large batteries. Large batteries have gas emissions that can cause the alarm to perform at less than optimum performance.
  • Do not obstruct the vents located on the alarm. Do not place the alarm where drapes, furniture or other objects block the flow of air to the vents.

My CO detector is beeping, what does it mean?

Your CO detector will beep primarily for two main reasons:

  • It has detected carbon monoxide and will alarm with continuous beeps, i.e. 4 or 5 beeps in a continuous fashion.
  • The battery is low and will "chirp" about once per minute to alarm that batteries need replacement.

Please read your CO alarm manual as the beeping sequence and their meaning may vary from manufacturer and model.

Shall I take my CO detector alarm serious?

Absolutely. Take action. Evacuate from your indoor surroundings and call 911.

To illustrate the seriousness, look at this example. In 2019, Illinois fire departments responded to 23,000 calls about CO and were able to determine a CO leak at nearly 11,000 of those locations - that is nearly 50%.

How do I take care of my Carbon Monoxide Alarm?

Your CO detector doesn't need much love. Just make sure to test it weekly by pressing the TEST button and change the batteries yearly. Make sure the vented slots are not clogged with any dust and follow the manufacturer's use and care booklet. If your unit operates off the battery, always use fresh alkaline or lithium batteries. Again, check to make sure it is operational, check the LED lights, the battery bar life, and press the test button. Typical maintenance steps include:

  • Test the alarm weekly by pressing the TEST button.
  • Check grilled vent slots to ensure no blockage.
  • Clean your CO alarm regularly to prevent dust build up.
  • This can be done using a vacuum cleaner with the brush attachment once per month. Clean gently around the front grilled vent slots.
  • Never use cleaning solutions on your alarm.
  • Do not paint the alarm.
  • Do not tamper with any of component as this may lead to a product fault and cause Risk of death.

co detect and alarm

Which CO levels are important? 

No standards for CO have been agreed upon for indoor air. This is the reason why various agencies, departments and organizations are referenced and each has different recommended exposure levels. Such differences has caused much confusion amongst the public.

To help, we have put a table together here to give you the lay of the land.





9ppm average over 8 hours



9ppm average over 8 hours



9ppm average over 8 hours



35ppm average over 10 hours

200ppm ceiling value


50ppm average over 8 hours



25ppm average over 8 hours


CO Detector Alarming Protocol
UL2034 (USA)

>70ppm (60 to 240 minutes)
>200ppm (10 to 50 minutes)
>400ppm (4 to15 minutes)
USA Carbon Monoxide Detectors

CO Detector Alarming Protocol
EN 50291:2001 (Europe)

>50ppm (60 to 90 minutes)
>100ppm (10 to 40 minutes)
>300ppm (3 minutes)

Europe Carbon Monoxide Detectors

Forensics Low Level Carbon Monoxide Detector

>25ppm (1 minute)

Forensics Detectors Low Level Detectors

What is a UL2034 CO Alarm? When does it alarm?

Nearly all carbon monoxide detectors that are mandated by city, county or state jurisdictions, require the CO detector to comply with the UL2034. Nearly all of the CO detectors you purchase from Home Depot, Lowes, Costco and other large retail stores are UL2034 compliant.

The UL2034 standard has specific requirements as to how the CO detector alarms and at what time and at what CO concentration. For example, the alarming protocol for a typical UL2034 carbon monoxide detector will audibly alarm when the CO concentration is:

  • >70ppm for 60 to 240 minutes
  • >200ppm for 10 to 50 minutes
  • >400ppm for 4 to15 minutes

However, please note that when you do purchase a CO Detector that is UL2034 compliant, the package or the manual will have text that reads something as follows:

Warning: This product is intended for use in ordinary indoor locations of family living units. It is not designed to measure compliance with Occupational Safety and Health Administration (OSHA) commercial or industrial standards. Individuals with medical problems may consider using warning devices which provide audible and visual warnings for carbon monoxide concentrations under 30 ppm.

co detector from costco

What is a Low Level CO Detector?

A low level carbon monoxide detector is a specially designed CO detector to provide added protection for older adults, elderly, pregnant women, young children, and persons with medical conditions who may be more vulnerable to the adverse health effects of exposure to low CO levels.

As we showed previously the a UL2034 CO detector is not designed to measure compliance with OSHA CO exposure. So to have that extra layer of protection from low level exposure and symptoms, a low level CO detector may be warranted.

For example, the FORENSICS low level CO detector triggers an audible alarm when CO detected > 25ppm. Such low-level CO alarming is closer to various government CO gas exposure limits compared to traditional alarming protocols of CO detectors following UL2034 (70ppm from 60-240minutes).

Again we emphasize, that a low level CO detector IS NOT a replacement for a UL2034 carbon monoxide detector which is mandatory per most local code and state legislation.

Is Carbon Monoxide gas is lighter or heavier than air?

Yes. Carbon monoxide is approximately 3% lighter than gaseous air.

Although factors such as molecular weight and temperature affect the rate of such diffusion, they do not influence the ultimate distribution of carbon monoxide gas and as such, placement of your CO detector is not affected. This has been shown to be true via experimental studies by Professor Hampson.

Are Carbon Monoxide Detectors reliable?

Yes they are mostly reliable and should not be a excuse NOT to purchase a CO detector.

In a 2011 study by Ohio University, 30 carbon monoxide detectors were tested. These were in use detectors and found that more than half failed to function properly, alarming too early or too late. Forty percent of detectors failed to alarm in hazardous concentrations, despite outward indications that they were operating as intended. 

Should I bring a carbon monoxide detector when traveling at a hotel, a boat, a plane?

Yes you should. You should bring with you a working carbon monoxide detector or a travel CO detector. Some hotels may have them installed and some may not. It often happens they are installed, but have dead batteries or are expired. Be on the safe side, always travel with a CO detector.

Should I have a Carbon Monoxide detector when I drive a car?

Yes you should. Forensics Detectors makes a vehicle CO Detector. Unfortunately there are vehicles that have shown to leak carbon monoxide in their cabins. For example:

  • Ford Explorer has been reported to leak carbon monoxide in the cabin and highlighted highlighted by the Center for Auto Safety.
  • Polluted outdoor air may enter your cabin as shown here by Dr. Koz.
  • Your vehicle may allow exhaust gas and carbon monoxide to enter the cabin via panel cracks, poor seals and holes, see here.

vehicle CO detector

Final Words

Be smart and get yourself a carbon monoxide detector. Install it in your home. Read the manual. Understand your combustion appliances in your home. Perform visual inspections and ensure all appliances are venting and exhausting correctly. Take care when using portable generators or any other equipment that uses fossil fuels. Maintain your CO detector and if you require added protection, also purchase a Low Level CO Detector for early warning.


References and Further Reading

The World Health Organization (WHO)

The WHO is a specialized agency of the United Nations that is concerned with international public health. To protect public health from risks due chemical exposure, WHO has published guidelines for toxic chemicals in indoor air. The guideline for carbon monoxide exposure is 9ppm over a time weighted average over an 8 hour period. (Reference: WHO. (2010). "WHO guidelines for indoor air quality: selected pollutants” ISBN 978 92 890 0213

The United States Environmental Protection Agency (EPA)

The EPA is a Federal agency concerned with air quality standards, and has set maximum standards for pollutants considered harmful to public health.   The Table Of Historical Carbon Monoxide National Ambient Air Quality Standards establishes a concentration of 9 ppm carbon monoxide time weighted average over an 8 hour period since 1971.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)

ASHRAE has created maximum standards for pollutants considered harmful to public health, and also establishes a concentration of 9 ppm carbon monoxide time weighted average over an 8 hour period. Source:

The National Institute for Occupational Safety and Health (NIOSH)

NIOSH is a Federal agency under the Department of Health and Human Services published a Recommended Exposure Limit of no more than 35ppm at a 10 hour time weighted average per day and a ceiling value of 200pm, where the ceiling value should not be exceeded at any time (Source:

The Occupational Health and Safety Administration (OSHA) 

OSHA is a Federal agency under the Department of Labor that develops and enforces federal standards for health and safety in the work place recommend a permissible exposure limit (PEL) of carbon monoxide to no more than 50ppm time weighted over an 8 hour work day.  Source:

The American Conference of Governmental Industrial Hygienists (ACGIH) 

ACGIH has assigned carbon monoxide a threshold limit value (TLV) of 25 ppm (29 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour work week [ACGIH 1994, p. 15] 

About The Author

Dr. Koz is the President of FORENSICS DETECTORS where the company operates from the scenic Palos Verdes Peninsula in Los Angeles, California. He is a subject matter expert on gas sensor technology, gas detectors, gas meters and gas analyzers. He has been designing, building, manufacturing and testing toxic gas detection systems for over 20 years.

gas detector expert

Everyday is a blessing for Dr. Koz. He loves to help customers solve their unique problems. Dr. Koz also loves spending time with his wife and his three children going to the beach, grilling burgers and having a cold beer. 

Read more about Forensics Detections here.

Phone: +1 424-341-3886


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