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, snow blowers, and other yard equipment
-
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 @ours. 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:
|
%
CoHb
|
Symptoms and
Medical Consequences
|
| 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. |
| 45% |
Unconsciousness. |
| 50%+ |
Death. |
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:
| PPM CO |
Time |
Symptoms |
| 35 PPM |
8 hours |
Maximum exposure
allowed by OSHA in the workplace over an eight hour period. |
| 200 PPM |
2-3 hours |
Mild headache,
fatigue, nausea and dizziness. |
| 400 PPM |
1-2 hours |
Serious headache-
other symptoms intensify, Life threatening after 3 hours. |
| 800 PPM |
45 minutes |
Dizziness, nausea
and convulsions, Unconscious within 2 hours. Death within 2-3
hours. |
| 1600 PPM |
20 minutes |
Headache, dizziness
and nausea. Death within 1 hour. |
| 3200 PPM |
5-10 minutes |
Headache, dizziness
and nausea. Death within 1 hour. |
| 6400 PPM |
1-2 minutes |
Headache, dizziness
and nausea. Death within 25-30 minutes. |
| 12,800 PPM |
1-3 minutes |
Death. |
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 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 re-samples 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 m' ' 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:
| Characteristic |
Household
Current |
Battery
Operated |
| Cost |
$30 –
$50 |
$30 –
$50 |
| Ease of
installation |
more
difficult -
requires outlet near detector or 'hard wiring'. |
Less difficult.
Can be placed anywhere needed. |
| Maintenance |
No 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. |
| Reaction Time/Exposure Level Display
|
Gives continuous
display Of CO levels updated every few minutes. |
Reaction Time depends on
concentration level and duration of exposure. Display information
is limited.
|
| Reset Time |
Will reset
immediately once Co problem is corrected.
|
Reset 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:
| Cause |
Preventive
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.
What
should I do when my carbon monoxide detector goes off?
First and foremost, stay calm. As mentioned previously most
situations resulting in activation of a carbon monoxide detector are
not life threatening and do not require calling 911. To determine the
need I to call 911, ask the following question of everyone in the
household:
"Does anyone feel ill? Is anyone experiencing the 'flu-like'
symptoms of headache, nausea or dizziness?"
If the answer to the above by anyone in the household is true,
evacuate the household to a safe location and have someone call 911.
Failure to evacuate immediately may result in prolonged exposure and
worsening effects from possible carbon monoxide gas. The best initial
treatment for carbon monoxide gas exposure is fresh air. If the
answer to the above by everyone in the household is no, the likelihood
of a serious exposure is greatly diminished and one probably does not
need to call 911. Instead, turn off any gas burning appliances or
equipment, ventilate the area and attempt to reset the alarm. If the
alarm will not reset or resounds, call a qualified heating and
ventilating service contractor to inspect your system for possible
problems. If at any time during this process someone begins to feel
ill with the symptoms described above evacuate the household to a safe
location and have someone call 911.
What
can I expect to happen if I call 911?
What to expect when calling 911 is based on the polices and
procedures of the public safety agencies serving your community and
will vary from area to area. Most public safety agencies are, however,
recognizing the dangers posed by carbon monoxide gas and are adopting
similar procedures to the ones described below. These procedures are
based on information developed by the International Association of
Fire Chiefs (IAFC) and other national and regional associations. The
objective of these procedures is to quickly determine the severity of
the situation and provide the proper emergency response. The following
is a summary of what one can expect to happen if the call 91 1 because
a carbon monoxide detector is sounding:
When initially calling 911 be prepared to provide the following
information:
-
Your address.
-
The type of detector that is sounding.
-
Whether or not anyone is feeling ill with 'flu-like' symptoms as
previously described.
-
Whether or not everyone has evacuated the residence.
-
The reading on the detector (if known or available)
The dispatcher will determine the response required based on the
answers to the above- most significantly whether or not anyone is
feeling ill.
If anyone is feeling ill and/or you can not or have not been able
to evacuate everyone, law enforcement, medical and fire personnel will
be assigned to the call on an emergency basis. Law enforcement to
assist with the immediate evacuation of individuals, medical to treat
any victims and fire to monitor for CO gas and assist with the other
activities.
If no one is feeling ill, you may be advised to contact your local
heating contractor or gas company to assist you or, fire
personnel will be dispatched on a routine basis to monitor for CO gas
and advise if a 'real' carbon monoxide problem exists.
As mentioned previously, response policies vary by community and
you may wish to call your local fire or police non-emergency number to
ask what their particular policies are.
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:
Manufacturer
|
Number
|
First Alert
|
800-323-9005
|
Jameson
|
800-779-1719
|
Nighthawk
|
800-880-6788
|
Quantum
|
800-432-5599
|
Additional information with product ratings is contained in the
Consumer Reports issue on home safety products.
Carbon Monoxide
(CO)
