Health effects from exposure to CO levels of approximately one to 70 ppm are uncertain, but many people will not experience any symptoms. As CO levels increase and remain above 70 ppm, symptoms may become more noticeable (headache, fatigue, nausea), see table 1. Senior citizens, people with heart or respiratory problems, small children and pregnant women are at the greatest risk.

Prevention is key

Stop the threat at the source. Make sure appliances are installed according to manufacturer's instructions and local building codes. Most appliances should be installed by professionals. Have the heating system (including chimneys and vents) inspected and serviced annually. The inspector should also check chimneys and flues for blockages, corrosion, partial and complete disconnections and loose connections. Pay attention to issues that may cause uneven air pressures in the house, such as duct leakage, a powered attic ventilator (these are not recommended, in part because of this issue) or inadequate supply air provided to a combustion appliance. The new generation of gas-fired tankless water heaters consume nearly twice as much combustion air as a traditional gas fired, tank water heaters—this makes “make-up” air twice as important. The Consumer Product Safety Commission has a whole litany of “no-brainer” issues.

• Never burn charcoal inside a home, garage, vehicle, or tent.
• Never use portable fuel-burning camping equipment inside a home, garage, vehicle, or tent.
• Never leave a car running in an attached garage, even with the garage door open.
• Never service fuel-burning appliances without proper knowledge, skills and tools. Always refer to the owner's manual when performing minor adjustments or servicing fuel-burning appliances.
• Never use gas appliances such as ranges, ovens, or clothes dryers for heating your home.
• Never operate unvented fuel-burning appliances in any room with closed doors or windows or in any room where people are sleeping.
• Do not use gasoline-powered tools and engines indoors.

In spite of the common sense approach of these “do not” points, folks still continue to fall victim to CO poisoning because of them.

Which is why installing a CO detectors is so important. A carbon monoxide detector/alarm can provide added protection, but is no substitute for proper use and upkeep of appliances that can produce CO.

How do CO detectors work?

CO exists in homes without gas stoves, on average, at a range from 0.5 to 5 parts per million (ppm). Those level rise to five to 15 ppm near properly adjusted gas stoves and may be 30 ppm or higher near improperly adjusted stoves. Based on a voluntary industry standard, a CO detector sends an alarm when levels reach 70 parts per million (ppm) for an hour, sooner at higher levels. Fuel-burning appliances are often the source of the problem.

Homeowners should remember not to install carbon monoxide detectors directly above or beside fuel-burning appliances, as appliances may emit a small amount of carbon monoxide upon start-up. A detector should not be placed within 15 feet of heating or cooking appliances or in or near very humid areas such as bathrooms. Install a CO detector/alarm in the hallway near every separate sleeping area of the home. Make sure the detector cannot be covered up by furniture or draperies. Don’t put alarms inside garages, where initially high CO from car exhausts can trigger false alarms, or near doors and windows, where fresh air can lead to a false low reading.

What to look for in a CO detector

According to Consumer Reports “The best alarms cost $75 or less and include interconnecting models that trigger each other so that all alarms sound when one sniffs out a threat. Some alarms combine CO and smoke detection.” (Basic carbon monoxide detector) In reviews, “experts prefer models with digital readouts, which continually display carbon monoxide gas levels in the home. Reviews say such displays can alert you to borderline CO gas levels that may not yet be considered dangerous, and offer assurance that the model is working properly.” CO detectors can range in cost upwards of $200 for models that monitor lower levels of CO.

Consider these points:

• Determine whether your local building code requires a specific type of CO alarm-- hardwired vs. a battery model. Shop for a unit that meets the requirements of the current UL standard 2034 or the requirements of the IAS 6-96 standard.
• Battery alarms are easier to install than plug-in or wired models. Cells for these and alarms with battery backup must be changed on a yearly basis.
• Digital displays show relatively precise CO levels in parts per million, rather than simply beeping. Some also show the peak level since they were reset, warning you of any spikes that occurred while you were away.
• Confirm the manufacture date. CO alarms lose sensitivity after five years. The manufacture date is on the back of the alarm; fresher is better.
• One CO alarm may be fine for small, one-level homes. For multilevel homes, consider an interconnecting alarm at each level to warn you of problems in remote parts of the house.
• Consider an alarm that combines CO and smoke detection

For more information:

Combustion Equipment Safety technical bulletin – www.southface.org/factsheets

Consumer Reports – www.consumerreports.org

Carbon Monoxide Kills - www.carbonmonoxidekills.com

Environmental Protection Agency - Protect Your Family and Yourself from Carbon Monoxide Poisoning www.epa.gov/iaq/pubs/coftsht.html

Consumer Product Safety Commission - Carbon Monoxide Questions and Answers, CPSC Document #466 www.cpsc.gov/CPSCPUB/PUBS/466.html

CO Experts - www.coexperts.com