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Carbon Monoxide Detectors

How to Test a Carbon Monoxide Detector

How to Check Your Carbon Monoxide Detector Expiration Date

Carbon Monoxide (CO) is a deadly gas produced by burning any fuel. When inhaled, CO rapidly displaces oxygen in the victim’s blood, resulting in serious illness, even death. Since Carbon Monoxide is completely invisible, odorless and tasteless, many people have no idea that they are being poisoned until it is too late. For this reason, CO is often called the silent killer. Airtight design in today’s modern energy efficient homes can contribute to the problem by confining CO contaminated air within the home.

The symptoms of CO poisoning often imitate those of common illnesses such as the flu. Some studies have indicated an estimated 23.6% of people who have flu or stress symptoms could actually be suffering from CO poisoning. Victims of low level CO poisoning often experience mild headaches, shortage of breath, nausea, drowsiness and dizzy spells. At higher levels, CO poisoning can cause severe headaches, mental confusion, impairment of vision or hearing, vomiting, fatigue, loss of consciousness, and coma. Severe CO poisoning can cause an irregular heartbeat, amnesia, brain damage, coma, and eventually death.

Medical studies have shown a high percentage of the population is particularly vulnerable to CO, including low levels over a longer period of time. This high-risk group includes fetuses, children, the elderly and those with heart and lung disorders. When inhaled, CO combines with hemoglobin in red blood cells to form substances that work to decrease oxygen levels and eventually asphyxiate the victim.

The Fire Marshals Association of North America shares the common belief that the awareness of the dangers of carbon monoxide combined with the use of CO detectors in the home, will dramatically reduce the incidents of tragic deaths and frightening near misses that result from CO leaks. Carbon monoxide is a common by-product of vehicle exhaust and appliances that run on flammable fuel. Appliances should always be checked to ensure they are in good working order and properly ventilated by a qualified professional if necessary.

It is recommended that at least one CO detector is installed in the sleeping area of your home, and even additional devices installed near other emission sources such as heating appliances.

The community needs to be aware of this hazard. Excellent information on carbon monoxide is available from a variety of manufacturers of Co detectors, as well as from your local gas utility company. Many common questions are answered in literature provided by these companies. They allow you to recognize the hazards of the various levels of CO poisoning, take practical steps to protect you and your family from CO poisoning, and provide first aid information that could save your life.

Frequently Asked Questions About Carbon Monoxide Detectors

What is carbon monoxide (CO) and why do I need a carbon monoxide detector?
Carbon monoxide is a colorless, odorless, tasteless and toxic gas produced as a by-product of combustion. Any fuel burning appliance, vehicle, tool or other device has the potential to produce dangerous levels of carbon monoxide gas. Examples of carbon monoxide producing devices commonly in use around the home include:

  • Fuel fired furnaces (non-electric)
  • Gas water heaters
  • Fireplaces and woodstoves
  • Gas stoves
  • Gas dryers
  • Charcoal grills
  • Lawnmowers and other yard equipment
  • Power Generators
  • Automobiles

The Consumer Products Safety Commission (CPSC) reports that approximately 200 people per year are killed by accidental CO poisoning with an additional 5000 people injured. These deaths and injuries are typically caused by improperly used or malfunctioning equipment aggravated by improvements in building construction which limit the amount of fresh air flowing in to homes and other structures.

While regular maintenance and inspection of gas burning equipment in the home can minimize the potential for exposure to CO gas, the possibility for some type of sudden failure resulting in a potentially life threatening build up of gas always exists.

What are the medical effects of carbon monoxide and how do I recognize them?

Carbon monoxide inhibits the blood’s ability to carry oxygen to body tissues including vital organs such as the heart and brain. When CO is inhaled, it combines with the oxygen carrying hemoglobin of the blood to form carboxyhemoglobin. Once combined with the hemoglobin, that hemoglobin is no longer available for transporting oxygen. How quickly the carboxyhemoglobin builds up is a factor of the concentration of the gas being inhaled (measured in parts per million or PPM) and the duration of the exposure. Compounding the effects of the exposure is the long half-life of carboxyhemoglobin in the blood. Half-life is a measure of how quickly levels return to normal. The half-life of carboxyhemoglobin is approximately 5 hours. This means that for a given exposure level, it will take about 5 hours for the level of carboxyhemoglobin in the blood to drop to half its current level after the exposure is terminated.

The following table describes the symptoms associated with a given concentration of COHb:

% COHbSymptoms & Medical Findings
10%No symptoms. Heavy smokers can have as much as 9% COHb.
15%Mild headache.
25%Nausea and serious headache. Fairly quick recovery after treatment with oxygen and/or fresh air.
30%Symptoms intensify. Potential for long term effects especially in the case of infants, children, the elderly, victims of heart disease, and pregnant women.

Since one can’t easily measure COHb levels outside of a medical environment, CO toxicity levels are usually expressed in airborne concentration levels (PPM) and duration of exposure. Expressed in this way, symptoms of exposure can be stated as follows:

Parts per million (PPM) COExposure TimeSymptoms
35 PPM8 hoursUsually none or slight headache. Maximum exposure allowed by OSHA in the workplace over an eight hour period.
200 PPM2-3 hoursMild headache, fatigue, nausea and dizziness.
400 PPM1-2 hoursSerious headache, other symptoms intensify. Life threatening after 3 hours.
800 PPM45 minutesSevere dizziness, nausea and seizures. Unconscious within 2 hours. Death within 2-3 hours.
1600 PPM20 minutesHeadache, dizziness and nausea. Death within 1 hour.
3200 PPM5-10 minutesHeadache, dizziness and nausea. Death within 1 hour.
6400 PPM1-2 minutesHeadache, dizziness and nausea. Death within 25-30 minutes.
12800 PPM1-3 minutesDeath.

As can be seen from the above information, the symptoms vary widely based on exposure level, duration and the general health and age on an individual. Also note the one recurrent theme that is most significant in the recognition of carbon monoxide poisoning- headache, dizziness and nausea. These ‘flu like’ symptoms are often mistaken for a real case of the flu and can result in delayed or misdiagnosed treatment. When experienced in conjunction with a the sounding of a carbon monoxide these symptoms are the best indicator that a potentially serious buildup of carbon monoxide exists. This comment will be returned to later.

What are the different types of carbon monoxide detectors and how do they work?

There are a number of different types and brands of carbon monoxide detectors on the market today; They can be most easily characterized by whether they operate on household current or batteries. Underlying this, in most cases, is the type of sensor employed in the detectors operation. Detectors using household current typically employ some type of solid-state sensor which purges itself and resamples for CO on a periodic basis. This cycling of the sensor is the source of its increased power demands. Detectors powered by batteries typically use a passive sensor technology which reacts to the prolonged exposure to carbon monoxide gas.

Are some types of detectors better than others? How do I select the best detector for me?

Regardless of the type of sensor used all detectors sold on the market today should conform to minimum sensitivity and alarm characteristics. These characteristics have been defined and are verified by Underwriters Laboratory in their standard for carbon monoxide detectors UL 2034. This standard was most recently revised in June of 1995 and went into effect in October of 1995. This revision specified additional requirements regarding identification of detector type, low-level (nuisance) alarm sensitivity and alarm silencing. Under no circumstances should one purchase a detector that is not UL listed.
Each of the two types of detectors mentioned previously has applications in the home along with associated advantages and disadvantages. The proper detector for each application or installation should be chosen based on the application requirements and the products specifications. The following are the principle advantages and disadvantages of the two different type detectors:

CharacteristicHousehold CurrentBattery Operated
Cost$30.00 – $50.00$30.00 – $50.00
Ease of InstallationMore difficult – requires outlet near detector or “hard wiring.”Less difficult. Can be placed anywhere needed.
MaintenanceNo maintenance required during life of product (5-10 years). Detector sensor becomes more sensitive with age.Requires periodic replacement of battery/sensor module every 2-3 years at a cost of $20.00 +/-
Reaction Time/Exposure Level DisplayGives continuous display of CO levels updated every few minutes.Reaction time depends on concentration level and duration of exposure. Display information is limited.
Reset TimeWill reset immediately once CO problem is corrected.Rest time depends on exposure concentration and duration. May require removal of sensor pack. A silence button, however is now provided/required.

How many carbon monoxide detectors should I have and where should I place them?

The Consumer Product Safety Commission recommends a detector on each floor of a residence. At a minimum, a single detector should be placed on each sleeping floor with an additional detector in the area of any major gas burning appliances such as a furnace or water heater. Installation in these areas ensures rapid detection of any potentially malfunctioning appliances and the ability to hear the alarm from all sleeping areas. In general, carbon monoxide detectors should be placed high (near the ceiling) for most effective use. Detectors should also not be placed within five feet of gas fueled appliances or near cooking or bathing areas. Consult the manufacturers installation instructions for proper placement of a detector within a given area.

What are the most common causes of carbon monoxide detector alarms?

There are many conditions which can cause a carbon monoxide detector to alarm. Most are preventable and few are actually life threatening. Ideally through proper placement of the detector and education of the users the number of preventable calls can be minimized and activation will only occur in the more serious situations.
Preventable causes of CO alarm activation and the recommended preventive action are as follows:

CausePreventive Action
Inadequate fresh air venting of the home.Have a heating contractor install a fresh air makeup system in the home.
Running gas powered equipment or automobiles in a home or garage.Gas powered equipment or vehicles should never be operated within a home or garage – even if the garage door is open. Since most homes are typically at a lower pressure relative to outside air, the gas can actually be drawn into the home.
Charcoal grilling in the home or garage.Charcoal grilling is a tremendous producer of Carbon Monoxide gas. Charcoal grills should never be operated in the home.
Malfunctioning appliances or equipment in the home.All fuel burning appliances or equipment in the home needs periodic inspection and preventive maintenance. While all fuel burning appliances will produce some CO gas, regular preventive maintenance can keep this to a minimum.
Malfunctioning or overly sensitive alarm.Buy only UL Listed alarms conforming to the latest revision (June 1995) of UL standard 2034. This revision includes new requirements to minimize nuisance alarms.

While many causes can be prevented others can not and may occur unpredictably. Not only are these problems harder to predict but they also tend to be more serious in nature. Examples of these type problems are:

  • Cracked furnace heat exchanger.
  • Malfunctioning furnace or water heater.
  • Blocked chimney.
  • Other unpredictable events- vehicle left running in garage, gas powered device placed near fresh air vent to home, etc.

Minimizing preventable events allows everyone to take other less preventable and predictable events more seriously.

Where can I get further information concerning carbon monoxide detectors?

Several manufacturers of carbon monoxide detectors offer toll free numbers for additional information regarding their products. These numbers are as follows:

American Sensors800-387-4219
First Alert800-323-9005

Where can I purchase carbon monoxide detectors Locally?

Scarborough Lumber and ACE Scarborough in Scotts Valley have a different styles and types of detectors in stock. The prices range from $29 to $49 depending on the brand and features. Also K-Mart on Mt Hermon Road has a good selection.

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