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Carbon Monoxide Alarms

How does a CO detector work?

There are three basic types of CO sensors metal oxide, biomimetic and electrochemical. Each is discussed in this chart. Note that while there may be performance differences between these technologies, all detectors are tested and approved for their operation. The retail cost of a detector will generally relate to the number of features included and its warranty conditions. There are performance differences between these detector types. However, changes to the CO standards should soon result in all detectors, regardless of detector type, having to undergo extensive testing. All will be certified to operate under different environments (various chemical exposures, different relative humidities, etc.) satisfactorily if they meet the standards.

Carbon Monoxide Alarm Features

Carbon monoxide alarms have a variety of different features. Before you buy one, take a few minutes to identify the features that will best serve your needs. Some features to check before you buy:

  • AC or battery operation
  • UL or CAS Listing
  • Purchase price
  • Yearly sensor and/or battery replacement cost
  • Consumer evaluations
  • Reliability of the company
  • Reset features and time it takes to reset and clear
  • Digital readout
  • Capacity to be wired with other alarms
  • Sensitivity
  • Memory and peak level functions

Combination Smoke and CO Alarm Technology
Two sensors in a single alarm. Separate sensors monitor the air for smoke and carbon monoxide.

Digital Display
Shows elevated levels of CO present in the air in parts per million (ppm). During an alarm, this readout can help investigators determine how serious the problem is.

Peak Level Memory
Remembers the maximum level of carbon monoxide that was present. This is important information about maximum exposure to assist investigators, emergency responders, or repair technicians to determine if the levels of carbon monoxide are reduced before the response to an alarm.

Hard-Wired (Electrical) Powered With Battery Back-Up
Wire it in. The alarm will be as permanent as a hard-wired smoke detector.The CO alarm must have a battery back-up in order to protect you from the presence of carbon monoxide that is generated from portable devices such as generators or kerosene heaters during electrical outages.

Plug-In (Electrical) Powered With Battery Back-Up
Plug it in! Just plug the CO alarm into a 120 VAC electrical outlet that isn't controlled by a switch or dimmer. The CO alarm must have a battery back-up in order to protect you from the presence of carbon monoxide that is generated from portable devices such as generators or kerosene heaters during electrical outages.

Battery Powered
Quick and easy use for almost anywhere. Ideal for areas where you don't have available electrical outlets. Remember to change your 9-volt battery in the spring and fall daylight savings time changes.

Low Battery Warning "Chirp"
Alerts you when the battery is low. The alarm will "chirp", reminding you to change the battery.

Remote Control Test / Silence
Allows you to ensure your CO alarm is functioning properly. Test or silence your CO alarm using most TV or VCR remote controls.

Test / Silence Button
One button performs two functions. In Test mode, it checks the horn and alarm functions. During an alarm, it activates the Silence Feature. Press it to temporarily silence the alarm.

Why do I need an a Carbon Monoxide alarm?

The U.S. Consumer Product Safety Commission identified Carbon Monoxide as the leading cause of gas poisoning deaths in the U.S. Thousands of cases of illness, brain damage and death could be prevented if all homes had CO alarms.

What type of alarm should I purchase?

Choose an alarm listed with the Underwriters Laboratory (UL) or Canadian Approval Services (CAS). The alarm sounds a shrill warning before the levels of Carbon Monoxide become immediately dangerous. Alarms cost $30 to $80.

Where should I place my alarm?

Carbon Monoxide is lighter than air. CO2 and O2 are products of complete combustion, CO is produced when there is incomplete combustion. If all 3 gases are spilled into an area the CO2 Carbon Dioxide will drop to the floor and the lighter CO Carbon Monoxide will always rise to the ceiling.

Another way to explain this is to compare it to smoke from a fire. Visible smoke from a fire is a particulate which is heavier than air, but it rapidly rises to the ceiling because of the heat. The same applies for CO spilled from an appliance, it will rise to the ceiling and will always be at a higher concentration near the ceiling.

Molecular weight of:

Carbon Monoxide----->28.01 Lighter

Nitrogen----------------->28.0134

Air------------------------->28.975

Oxygen------------------>32.00

Carbon Dioxide------->44.01 Heavier

Alarms should be located near each sleeping area. The alarm must be located where Carbon Monoxide can reach it, and where it will awaken persons sleeping in the dwelling. Homes with several sleeping areas will require multiple alarms. Locate additional alarms near fossil fuel appliances. Do not locate an alarm in a garage, kitchen or furnace room. CO alarms should be at least 15 feet from the furnace, water heating or cooking appliances. Do not mount them in dusty, dirty or greasy areas, or in extremely humid areas. Read and follow installation instructions furnished with the alarm.

What should be done if an alarm sounds?

EVACUATE and call 911. Make certain to account for everyone. Let the Fire Department determine if there is Carbon Monoxide in the home. If there is no CO present, follow directions supplied with the alarm.

What do I do if there is Carbon Monoxide in my home?

DO NOT IGNORE THE ALARM. Find out what caused the alarm. Contact your heating contractor for help in tracking down the CO source. Do not assume that because you cannot see, taste or smell anything, that there is no problem. CO has no color, taste or odor. Episodes of CO leakage can be sporadic and hard to detect. Be persistent. Field studies indicate there are few, if any, "false" alarms. Be certain there is always an operating alarm in any house where an alarm has sounded. It is important to respond to the alarm before continued exposure disables the occupants.

How do I know if the concentration is low or high?

Most CO alarms emit a loud, annoying sound. Alarms listed by UL sound only at levels above generally accepted safety levels. You will hear it. Some alarms have a digital readout, which reports the CO levels. But very low CO levels, those which cause chronic health problems, must be measured using professional instruments. Still other alarms have a color sensor, which can be evaluated by trained technicians.

How do I maintain and test the alarm?

Read and follow all instructions. In general, most alarms should be vacuumed at least twice a year, and tested every week. Most alarms have a test button which is pressed until a loud noise sounds. If the alarm fails to test properly, have it repaired or replaced immediately.



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