• Carbon Monoxide (CO) is a poisonous gas.
• Typical CO exposure guidelines are for healthy adults.   
• Children, pregnant women, the elderly, people who are immunocompromised or have cancer, or those with allergies, breathing issues, heart issues, and other health conditions can be at greater risk from exposure to CO. 
• People can be poisoned by small amounts of CO over a long period of time. 
• Exposure to low levels of CO can produce symptoms that mimic many common symptoms such as having a cold or flu, including headaches, fatigue, shortness of breath, nausea, and dizziness. 
• Many fire districts will evacuate the occupants of a home/building if their professional CO monitor reads 35 ppm or less.  The Maryland Fire and Rescue Institute advises that homeowners should leave their homes immediately and stay out until repairs are made if CO levels are above 10 ppm. 
• Doctors don't normally test for exposure to CO. 
• When homeowners were asked what they would do if their CO detector alarm activated while they were at home, the overwhelming response we received during interviews was that they would "remove the batteries."
• Furnaces, water heaters, and boilers can be major sources of carbon monoxide. 
• UL 2034-rated CO detectors have specific levels of CO that must be present for a defined period of time before the detector will alarm.   

30 ppm (parts per million) of CO must be present for at least 30 days before it will alarm. 

70 ppm of CO must be present for 1-4 hours before it will alarm

150 ppm of CO must be present for 10-50 minutes before it will alarm

400 ppm of CO must be present for 4-15 minutes must be present before it will alarm

• Current standards require CO detectors with a visible display panel to show "O" when CO levels of 29ppm or less are present.
• The CO detector manuals we reviewed stated that the detector should be tested on a regular basis.
• Multiple governmental agencies and regulatory agencies (e.g., EPA, OSHA, WHO, FEMA, ASHRAE, and more) have differing opinions on CO exposure levels and what is deemed "safe."
• The 5 to 10-year rating on the consumer CO detector packaging can be confusing as it can apply to the battery life, lifespan of the CO sensor, or the device. 
• Always read the CO detector's manual.
• CO detectors are not a replacement for properly maintaining a furnace or other fuel-burning appliances and their respective exhaust systems.