Originally published Friday, January 19, 2018 at 06:00a.m.

Our home has carbon monoxide monitors. We recently had our fire alarms replaced and the contractor told us that the carbon monoxide alarm is installed too high on the wall to be protective. Where should alarms be installed? — Don, Prescott Valley

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is slightly less dense than air. When CO enters a home the CO molecules displace the oxygen in a body and leads to poisoning and possibly death. It is toxic to animals, both invertebrate and vertebrate, and humans when encountered in concentrations above about 35 ppm.

Since CO has no odor, color or taste, it cannot be detected by our senses. This means that dangerous concentrations of the gas can build up indoors and humans have no way to detect the problem until they become ill. Furthermore, when people become sick the symptoms are similar to the flu, which can cause victims to ignore the early signs of CO poisoning.

Carbon monoxide poisoning can be prevented with simple actions such as installing a CO alarm and maintaining fuel burning appliances.

CO is produced whenever a material burns. Homes with fuel-burning appliances or attached garages are more than likely to have CO issues. Common sources of CO in homes include fuel-burning appliances and devices such as: clothes dryers; water heaters; furnaces or boilers; fireplaces, both gas and wood burning; gas stoves and ovens; motor vehicles; grills; generators; power tools; lawn equipment; wood stoves; and tobacco smoke. CO is all around us.

Carbon monoxide alarms should be installed in at least two areas in the home: outside of the bedrooms, approximately thermostat level, which is 5 feet or lower; the second alarm should be installed in the kitchen area.

There are several alarms on the market at assorted prices. The least expensive alarms only register a lower parts per million, i.e. 70 ppm. It is important to have an alarm that registers sensitivity at higher levels 10 ppm outside of the sleeping areas and lower sensitivity in the kitchen area. I recently purchased two of the Defender CO Alarms and they are not inexpensive, but have fabulous combustion safety features should anything go wrong.

It is important to properly vent and maintain fuel-burning appliances and they should all be vented to the outside.

Fuel-burning appliances should be regularly checked by a qualified heating contractor every year to look for potential problems. Just this past week, two homes were “red tagged” because the heating units had CO leaks that could have developed into a hazardous situation for the homeowner.

You should know the signs of CO leaks: Streaks of soot around fuel-burning appliances, or fallen soot in a fireplace, absence of an upward draft in your chimney, excess moisture and condensation on windows, walls and cold surfaces, rusting on flue pipes or appliance jacks, orange or yellow flame in combustion appliances (the flame should be blue), or damaged or discolored bricks at the top of the chimney.

Do not run or idle your vehicle in an attached garage. Instead, back your vehicle out right away.

Silent Killer

The symptoms of CO poisoning are difficult to identify because the symptoms are similar to the flu. CO is often called the “silent killer” because people will ignore early signs and eventually lose consciousness and be unable to escape to safety.

For most people, the first signs of exposure include mild headache and breathlessness with moderate exercise. Continued exposure can lead to more severe headaches, dizziness, fatigue and nausea. Eventually symptoms may progress to confusion, irritability, impaired judgment and coordination, and loss of consciousness.

You can tell the difference between CO poisoning and the flu with these clues:

• You feel better when you are away from home;

• Everyone in the home is sick at the same time;

• The family members most affected spend the most time in the house;

• Indoor pets appear ill;

• You don’t have a fever or body aches, and you don’t have swollen lymph nodes that are common with the flu and some other infections; and,

• Symptoms appear or seem to get worse when using fuel-burning equipment.

Some people at greater risk of CO poisoning. Individuals with respiratory conditions, such as asthma or emphysema, cardiovascular disease, anemia or sickle cell anemia, and also the elderly and young children, are at a greater risk for CO poisoning than adults. Remember, ANYONE can become sick and die from CO poisoning when exposed to very high levels.

At a glance

Following are effects, Inhalation Time and Toxic Symptoms Developed at ppm:

• 1-2 ppm — Might be normal, from cooking stoves, spillage, outdoor traffic.

• > 2 ppm — Raises questions about why CO is elevated. Source should be identified.

• 15 ppm — UL standards for residential detectors require that they NOT alarm at 15 ppm unless exposure is continuous for 30 days.

• 20 ppm — Typical concentration in flue gases (chimney) of a properly operating furnace or water heater.

• 27 ppm — Cardiorespiratory complaints.

• 50 ppm — Maximum allowable eight-hours workplace exposure.

• 75 ppm — Significant decrease in oxygen reserve.

• 80 ppm — Many residential detectors might alarm after several hours exposure.

• 100 ppm — UL listed detectors must sound a full alarm within 90 minutes or less. Slight headache, tiredness, dizziness, nausea after several hours exposure.

• 200 ppm — Slight headache, tiredness, dizziness, nausea after two to three hours, might be life-threatening in long exposures.

• 400 ppm — UL listed detectors must sound a full alarm within 15 minutes. Frontal headaches within one to two hours, life-threatening after three hours.

• 500 ppm — Often produced in garage when a cold car is started in an open garage and warmed-up for two minutes.

• 800 ppm — Dizziness, nausea and convulsions within 45 minutes. Unconsciousness within two hours. Death within two to three hours.

• 1,600 ppm — Headache, dizziness and nausea within 20 minutes. Death within one hour. Smoldering wood fires, malfunctioning furnaces, water heaters, and kitchen ranges typically produce concentrations exceeding 1,600 ppm.

• 6,400 ppm — Headache, dizziness and nausea within one to two minutes. Thinking impaired before response possible. Death within 10 to 15 minutes.

• 12,800 ppm — Death within one to three minutes.

How long do CO alarms last?

The typical lifespan of a CO alarm is between five and seven years, but it varies by manufacturer. Consult the product packaging or manufacturer for a recommended replacement date.

What do I do when my CO alarm sounds?

Don’t ignore a CO alarm if it is sounding. If people in the home are exhibiting symptoms of CO poisoning, immediately leave the building and call your local fire department. In cases where residents are feeling fine, call your local gas utility company or a qualified technician to help identify the cause of the problem.