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Carbon monoxide (CO) is a colorless, odorless and tasteless gas that is poisonous and potentially lethal. CO is a by-product of incomplete combustion. It is produced when flammable fuels such as natural gas, propane gas, heating oil, kerosene, coal, charcoal, gasoline or wood burns with insufficient oxygen.
                    

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Carbon Monoxide Technology
There are three technologies commonly utilized in residential carbon monoxide alarms. NADI is committed to using those components and technologies, which in its opinion are most suitable in each circumstance based on the following criteria:

A proven history of reliability,
Appropriate for the purpose intended,
Recognized by ULC, ULI or BSI as quality components.

Currently the technology employed by NADI’s carbon monoxide alarms (CO alarms) is semiconductor and biomimetic. All CO alarms sold by NADI have been tested by the independent laboratories ULI, ULC and BSI for compliance to relevant standards and carry the mark of the testing laboratory. Every NADI CO alarm is tested with real carbon monoxide gas in an ISO 9002 factory before it is sold. NADI’s Quality Assurance group strictly audits the manufacturing process and ULI, ULC and BSI conduct periodic inspections.

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Semiconductor Sensors
Semiconductor sensors utilize a controlled quantity of tin dioxide (SnO(2)) as a sensing element. The sensing material is heated by a small electric heating element and carbon monoxide gas is catalytically broken down at the surface of the sensing element. Electrons are released in this process and are absorbed by the sensing element. This increase in charged particles lowers the resistance of the sensor.

In an alarm using semiconductor sensors, electronics are used to measure the sensor resistance and from this to calculate the carbon monoxide concentration.

Semiconductor sensors are mechanically simple and are electronic in nature therefore, they are very long-lived and very reliable. Current designs demonstrate excellent immunity to other gases that may be present.

Millions of semiconductor CO alarms manufactured over the past ten years have provided historical data, which demonstrates a dependable sensor life of more than ten years.

Because of this positive history, the results of hundreds of tests by ULC, ULI and BSI over many years, and proven consistency in manufacture, this is the principle technology used by NADI.

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Biomimetic Sensors
Biomimetic sensors utilize a material that mimics the response of human hemoglobin to carbon monoxide. In the presence of carbon monoxide gas, the amount of infrared light which will pass through the sensing material declines. Alarms using this kind of sensor use external circuitry to monitor the transmittance of infrared light through the sensor. The rate of change of the transmittance is used to calculate carbon monoxide gas concentrations.

Biomimetic sensors demonstrate acceptable immunity to other gases that may be present.

Biomimetic sensors are mechanically simple devices.

Alarms using these sensors have field demonstrated a dependable sensor life in excess of three years.

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Electrochemical Sensors
Electrochemical sensors typically use platinum as a catalyst and acid as an electrolyte to break down carbon monoxide gas and release electrons. The electrons induce a small current, which creates a change in potential at external measurement points. Alarms utilizing this type of sensor use external circuitry to monitor the changes in potential and use this information to calculate the concentration of CO gas.

Electrochemical sensors are mechanically much more complex than semiconductor sensors but can provide more accurate measurements of CO concentrations. Modern electrochemical sensors demonstrate good immunity to interferent gases.

Careful design and processing is necessary to ensure accuracy across humidity extremes. Historically, electrochemical sensors have been prone to leakage due to:  
a) Corrosion of electrical contacts
b) Destruction of sealing surfaces in the body of the sensor
c) Expansion of the electrolyte volume

 Alarms using these sensors have not field demonstrated a dependable sensor lifetime in excess of 2 years.

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How NADI Carbon Monoxide Alarms Work

NADI carbon monoxide alarms (under the brand name "American Sensors") sample the air for CO every 1 to 3 minutes. When a unit detects a certain pre-programmed level of carbon monoxide, the alarm's microprocessor will store this information and measure the CO level against time. If the CO level is low or is present only for a short time, the alarm will ignore it and burn the sensor clean (so the sensor does not accumulate CO and cause the unit to nuisance alarm). However, if the CO level is high or if a low CO level remains for a pre-programmed period of time, the alarm will sound an alarm. This programming effectively minimizes the occurrence of nuisance alarms.

All NADI carbon monoxide alarms are Listed by Underwriters Laboratories Inc. UL 2034 and/or Underwriters Laboratories of Canada.

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Facts About Carbon Monoxide
Carbon Monoxide (CO) is an invisible, odorless, tasteless gas. Due to its high toxicity, CO is called the “silent killer”. Hundreds of thousands of North Americans require medical care each year because of CO poisoning. 

The human body depends on oxygen to convert food to usable energy that allows cells to live and function. Oxygen makes up approximately 21% of the atmosphere, and enters the lungs during breathing. In the lungs it combines with a blood component called hemoglobin. 

When saturated with oxygen, it is called oxyhemoglobin.  

After being carried by the bloodstream to the cells of the body, oxyhemoglobin releases oxygen to the body tissues. Carbon Monoxide is dangerous because it bonds much more tightly to the hemoglobin than oxygen does. Once hemoglobin combines with Carbon Monoxide to form carboxyhemoglobin, its ability to combine with oxygen is completely lost. 

As carboxyhemoglobin is formed, the amount of oxygen carried to the cells and organs in the body decreases. Carbon Monoxide starves the blood of oxygen, literally causing the body to suffocate from the inside out. When the carboxyhemoglobin concentration reaches a certain level, people get nauseous, become unconscious, and ultimately die. How quickly symptoms appear depends upon the concentration, or parts per million (ppm) of carbon monoxide in the air and the duration of exposure. A person’s size, age and general health are also factors in how quickly effects of the gas will become evident. 

Note:    Oxygen & CO is approximately the same density. They mix equally well in air. Therefore most alarms measuring CO can be placed anywhere in the room. Smoke alarms on the other hand should be placed higher up – i.e., on the ceiling.

The Consumer Product Safety Commission recommends only alarms that meet Underwriters Laboratory Standard 2034. Alarms that have the UL/ULC mark on the product meets the rigorous standards of performance, safety and accuracy. 

The current versions of UL2034 and CGA6019 (CSA6019) have harmonized sensitivity limits as defined below: 

• no alarm and no display reading below 30 ppm

• will go into alarm in 60 to 240 minutes at exposures of 70 ppm 

• will go into alarm in 10 to 50 minutes at exposures of 150 ppm 

• will go into alarm in 4 to 15 minutes at exposures of 400 ppm
  
  
  Carbon Monoxide (ppm CO) vs. Time (minutes)
  
  
  
  

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How Carbon Monoxide is Generated in the Home

Carbon Monoxide is generated through incomplete combustion of fuel such as natural gas, propane, heating oil, kerosene, coal, and charcoal, gasoline or wood. 

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Symptoms Of Carbon Monoxide Poisoning
Carbon Monoxide poisoning can happen to anyone, anytime, almost anywhere. While anyone is susceptible, experts agree that unborn babies, small children, senior citizens and people with heart or respiratory problems are especially vulnerable to Carbon Monoxide and are at the greatest risk for death or serious injuries.  

Infants and children are especially vulnerable to Carbon Monoxide due to their high metabolic rates. Because children use more oxygen faster than adults do, deadly Carbon Monoxide gas accumulates in their bodies faster and can interfere with oxygen supply to vital organs such as the brain and the heart. Unborn babies have an even higher risk of Carbon Monoxide poisoning and Carbon Monoxide poisoning in pregnant women has been linked to birth defects. 

Carbon Monoxide poisoning is often confused with the flu. It is important that you discuss with all family members the symptoms of Carbon Monoxide poisoning. Different Carbon Monoxide concentrations and exposure times cause different symptoms.  

Extreme Exposure:                Unconsciousness, convulsions,    
cardio respiratory failure, and death

 Medium Exposure:                Severe, throbbing, headache, 
                                                drowsiness, confusion, vomiting, 
                                                and fast heart rate

 Mild Exposure:                     Slight headache, nausea,   
                                                fatigue, (often described as 
                                                “flu-like” symptoms)

 For most people, mild symptoms generally will be felt after several hours of  exposure of 100 ppm’s of Carbon Monoxide.

 Many reported cases of Carbon Monoxide poisoning indicate that while victims are aware they are not well, they become so disoriented that they are unable to save themselves by either exiting the building or calling for assistance. Also, due to small size, young children and household pets may be the first affected.  

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The Long Lasting Effects of CO Poisoning
If left unchecked, a child’s exposure to Carbon Monoxide can lead to neurological disorders, memory loss, personality changes and mild to severe forms of brain damage. 

If a child complains or shows signs of headaches, dizziness, fatigue or nausea or diarrhea, he or she could have Carbon Monoxide poisoning. Be especially aware of symptoms that disappear when the child is out of the house and reappear upon return, or symptoms that affect the entire household at once. 

Since the symptoms closely mimic viral conditions such as the flu, without the fever, Carbon Monoxide poisoning is often treated improperly, if at all. 

A physician can perform a simple blood test (called a carboxyhemoglobin test) to determine the level of Carbon Monoxide in the bloodstream. If elevated levels of Carbon Monoxide are present, hyper baric (high-pressure) oxygen treatment may be used to rid the body of CO. A physician will make this determination and administer treatment if necessary. 

Children with Carbon Monoxide poisoning have mistakenly been treated for indigestion.

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Where To Install A Carbon Monoxide Detector
Since carbon monoxide moves freely in the air, the suggested location is in or as near as possible to sleeping areas of the home. The human body is most vulnerable to the effects of carbon monoxide during sleeping hours. To work properly the unit must not be blocked by furniture or draperies. Carbon Monoxide is virtually the same weight as air and therefore the alarm protects you in a high or low location.

For maximum protection, a carbon monoxide detector should be located outside primary sleeping areas or in each level of your home.

In the figure below are suggested locations in the home. The electronic sensor detects carbon monoxide, measures the concentration and sounds a loud alarm before a potentially harmful level is reached.

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Where NOT to Install a CO Detector
Some locations may interfere with the proper operation of the alarm and may cause false alarms or trouble signals.
CO detectors should not be installed in the following locations:

•  Where the temperature may drop below 4.4^o C (40^oF) or exceed 37.8^oC (100^oF).

• Near paint thinner fumes or household cleaning products. Ensure proper ventilation when using these types of chemicals.

• Within 1.5m (5 feet) of any cooking or open flame appliances such as furnaces, stoves and fireplaces.

• In exhaust streams from gas engines, vents, flues or chimneys.

• Do not place in close proximity to an automobile exhaust pipe; this will damage the detector.

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  How Can You Test/Reset the CO Alarm?
  A green power light indicates that power is supplied.
  To test the alarm (wait at least 10 minutes after installing the alarm); press and release the Test/Reset button. The alarm will beep and a red light will flash.

  To reset after an alarm, press the Test/Reset button to silence or reset the unit. Follow the instruction in "What to do in a CO Alarm Condition", Section 14 below, which tells you what to do after the alarm sounds. The American Sensors Carbon Monoxide alarm is designed to do a continuous self-diagnostic check of its micro processing circuitry when in use.

  A malfunctioning unit is indicated by a continuing intermittent single beep and flashing green and red light. If this occurs, reset the unit. If the unit again beeps intermittently, do not use this unit.
  
  Do not use car exhaust or intentionally introduce carbon monoxide through other methods. These methods are dangerous to you and the pollutants from car exhaust may damage the unit.
  
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  How to Maintain a Carbon Monoxide Alarm
  A CO alarm is useful only if it works. The following illustration explains proper maintenance:

  The unit should be tested at least once per month by pushing the Test/Reset button as outlined in "How Can You Test/Reset the CO Alarm?", Section 12 above.
  

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What To Do In A Carbon Monoxide Alarm Condition
If harmful levels of carbon monoxide are detected, your unit will go into alarm. (The alarm is a repeating pattern of 4 red LED flashes with beeps followed by a 5 second pause.)

  WARNING!

Actuation of a CO detector indicated the presence of carbon monoxide (CO) which can kill you. If the alarm signal sounds:

1. Push the reset/silence button;

2. Call the emergency services;

3. Immediately move to fresh air - outdoors or by an open door/window. Do a head count to check that all persons are accounted for. Do not reenter the premises nor move away from the open door/window until the emergency services responders have arrived, the premises have been aired out, and your alarm remains in its normal condition.

4. After following steps 1 to 3, if your alarm reactivates within a 24 hour period, repeat steps 1 to 3 and call a qualified technician to investigate for sources of CO from fuel burning equipment and appliances, and inspect for proper operation of this equipment. If problems are identified during this inspection have the equipment services immediately. Note any combustion equipment not inspected by the technician and consult the manufacturers' instruction, or contact the manufacturers directly, for more information about CO safety and this equipment. Make sure that motor vehicles are not, and have not been, operating in an attached garage or adjacent to the residence.
   
   What to do after resetting the unit following an alarm?
   A full continuous alarm within six minutes after rest confirms ongoing presence of harmful levels of carbon monoxide. If this occurs follow instructions 1 to 3 above.
   
   
   
   What to do after a carbon monoxide problem has been corrected?
   After a carbon monoxide problem has been corrected reset your alarm by pushing the Test/Reset button.
   

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Carbon Monoxide Statistics
Every year 1,700 people die from accidental carbon monoxide poisoning in North America. Over 10,000 others are treated or hospitalized annually. Carbon monoxide is the number one source of accidental poisoning deaths.

A 1984 paper by The Mayo Clinic reports that actual CO poisoning figures may be significantly higher than current statistics indicate, as reporting and recording procedures for carbon monoxide incidents are either not efficient or non-existent. They report that a study done in a south-west U.S. hospital indicated that 20% of patients seeking aid for chronic flu symptoms were found to have elevated levels of carbon monoxide.

The American Lung Association, The Lung Association (Canada), the Consumer Products Safety Commission, the American Medical Association and the Consumer Health and Safety Coalition have all declared carbon monoxide poisoning a primary concern and encourage consumer awareness and education.

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