Carbon Monoxide Poisoning: Selecting a Carbon Monoxide Detector (AEN-168)

ISU Extension Publication #: AEN-168
Author: Dr. Thomas Greiner, Dept. of Agricultural and Biosystems Engineering
Iowa State University
Date: 7/96

What is carbon Monoxide?

Carbon monoxide (CO) is a colorless, odorless, tasteless, deadly gas. You can’t see, smell or taste it. Carbon monoxide is slightly lighter than air and quickly spreads throughout an entire house.

What produces carbon monoxide?

Carbon monoxide gas is produced when fossil fuel burns incompletely because of insufficient oxygen. During incomplete combustion, carbon and hydrogen combine to form carbon dioxide, water, heat, and deadly carbon monoxide. In properly installed and maintained appliances gas burns clean and produces only small amounts of carbon monoxide. Anything that disrupts the burning process or results in a shortage of oxygen can increase carbon monoxide production. Wood, coal, and charcoal fires always produce carbon monoxide, as do gasoline engines.

Why do I need a carbon monoxide detector?

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 residences had CO detectors.

What type of detector should I purchase?

Choose a detector listed with Underwriters Laboratory (UL). The detector sounds a loud alarm before the levels of carbon monoxide become immediately dangerous. Detectors cost $30 to $80.

What about the small, inexpensive detection cards?

CO detection cards, with a chemical dot which changes color when exposed to carbon monoxide, must be visually checked for the presence of carbon monoxide. They do not sound an alarm and require regular checks. Although inexpensive, $4 to $18, they do not offer sufficient protection to be used as a primary detector.

Should I buy a detector powered by battery or AC house current?

Both battery and AC powered detectors have advantages. The battery operated detector is easy to install, easy to move, and operates during power outages, when emergency heating systems might be in use. A plug-in detector does not depend on a battery and does not require battery and sensor replacement. AC line powered detectors with battery back-up are also available at a slightly higher cost. And detectors wired together, so they all sound when CO is detected by any detector, offer even more protection.

What are some features to check before I buy?

  1. AC or battery operation
  2. UL Listing
  3. Purchase price
  4. Yearly sensor and/or battery replacement cost
  5. Consumer evaluations
  6. Reliability of the company
  7. Reset features and time it takes to reset and clear
  8. Digital readout
  9. Capacity to be wired with other alarms
  10. Sensitivity

Where do I put my CO detector?

Detectors should be located near each sleeping area. The detector must be located where carbon monoxide can reach it, and where the alarm will awaken persons sleeping in the dwelling. Homes with several sleeping areas will require multiple detectors. Locate additional detectors near fossil fuel appliances. Do not locate a detector in a garage, kitchen or furnace room. CO detectors 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 detector.

What levels of carbon monoxide do detectors measure?

The detectors are designed to protect against acute high levels of carbon monoxide. They are NOT required to warn of low-levels of CO. The UL standard requires detectors to alarm within 90 minutes when exposed to 100 ppm; 35 minutes when exposed to 200 ppm and 15 minutes when exposed to 400 ppm. Some detectors are more sensitive and will, when exposed for many hours, detect or alarm at lower levels. If you think you are suffering from chronic, low level exposure to carbon monoxide below the detection level of residential detectors, contact your doctor immediately and have your home checked by a professional, with equipment to detect lower concentrations.

What should be done if a detector alarms?

If you feel symptoms of CO poisoning EVACUATE and call 9-1-1. Make certain everyone is accounted for. If you don’t have symptoms of CO poisoning, ventilate the house, press the reset button (if your detector has one), turn off the potential sources of CO, and have the home checked by a qualified professional. FOLLOW THE DIRECTION SUPPLIED WITH THE DETECTOR. The instructions depend on the kind and date purchased and the features available. For instance, some detectors have a combination of reset buttons, silencing features, malfunction indicators, test buttons, visual indicators, operating indicators, low battery warnings, warning alarms, and full alarms. Some detectors have warning alarms, which sound at low levels, and a full alarms, which sound at high levels. Some detectors are more sensitive than others.

Is calling for emergency assistance always necessary?

No. If no one has CO symptoms, the above procedure, including having the home checked by a qualified professional, can be used.

What should be done after a CO detector alarms sounds and the people are safe?

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 can’t see, taste, or smell anything, there is no problem. Carbon monoxide has no color, taste, or odor. Find the CO source. Determine why the CO remained in the house rather than vent to the outdoors. Episodes of CO can be sporadic and hard to detect. Be persistent. Once doors and windows are opened, the CO source is difficult to determine. If your detector alarmed there is a reason. Field studies indicate there are few, if any, “false” alarms. Do not rest until you have an answer as to why the detector alarmed. Be certain there is always an operating detector in any house that has experienced an alarm. Carbon monoxide poisoning causes confusion, irrational thinking, memory loss, and fatigue. The detector will alarm before these symptoms occur. 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?

Some detectors have a digital readout which reports the CO levels. Other detectors have a color sensor which can be evaluated by trained technicians to determine the CO level. Detectors listed by UL are required to sound only at levels above generally accepted safety standards. Low levels, which can cause chronic health problems, must be measured using professional instruments.

How do I maintain and test the detector?

Read and follow all instructions. In general, most detectors should be vacuumed at least twice a year, and tested every week. Most detectors have a test button which is pressed until a loud alarm sounds. If the detector fails to test properly, have it repaired or replaced immediately. Carbon monoxide detectors save lives and prevent serious health side affects. Make sure your home and family is protected with a relatively small investment in at least one CO detector.

For more information request other notes in the Carbon Monoxide series. Agricultural Engineering Notes (AEN’s) are informally published information releases on topics of current concern to Iowans.