| Why Wait for the Alarm | What is CO | Health Effects | Alarm Standards |
What is carbon monoxide?
Carbon monoxide is a toxic gas that can occur in homes and buildings where combustion by-products are generated or allowed to disperse. It is colorless, odorless, tasteless and non-irritating; it is an asphyxiant. As a poison, it can be deadly at high levels. At low concentrations, CO can go undetected and contribute to nagging illnesses. It can compound pre-existing health problems and can go unblamed in premature deaths.
How is carbon monoxide formed?
How is it measured?
Carbon monoxide is a condition of unburned fuel. Fossil fuels and their by-products used for heat energy need proper amounts of oxygen for complete combustion and controlled temperature production. We are mixing the molecules of oxygen from our air (which makes up 20.9% of our air with nitrogen (N) making up almost 79% of the remaining) with molecules of fuel and igniting them. If we have completely burned all of our molecules of fuel and discharged the remaining by-products out of the way, we should not have any measurable molecules of CO.
Carbon monoxide is measured in parts per million (PPM); the
number of CO molecules present in a million molecules of air.
CO is also measured and
referenced as CO air free.
This is a unit of measurement designed to compensate for the excess air to the
burner and is taken from a flue gas sample.
Manufacturers of combustion systems must meet CO air free maximum
concentration limits in order to produce their products.
CO may be referenced as CO in PPM or CO in
PPM air free. CO air free
is a calculation based upon flue gas measurements of carbon monoxide (CO) and
oxygen (O2).
Whatever your application needs, you will need test instruments to complete this work. Please inquire about sensor life, calibration, cross sensitivities, maintenance and other features when you buy your Bacharach product. You may need an electronic instrument that calculates CO air free or you may simply need a quality CO instrument with a single sensor. You may wish you had both. Perhaps a CO data logger fits your needs.
Monoxor II PCA Sentinel
CO alarms
are warning devices.
How many of the buildings we enter have working and properly placed carbon monoxide alarm detectors? Are we recommending the placement of these alarms? Before we tell the consumer where to put CO alarms, we’ve got to understand building pressures and air movement in buildings as well as combustion, draft, make-up air and other aspects of carbon monoxide generation.
Is there a best location for CO alarms? Do we understand how carbon monoxide alarms work? Do we know the alarm standards? Can we explain these to the consumer?
Are we alerting the consumer to potential and foreseeable hazards associated with any of their combustion systems? Are we educating the public as we service them or are we merely billing them? We have opportunities to educate them.
Every building we enter that has combustion system influences should have a CO alarm.
If
one is not in place upon your visit, suggest their installation.
This should also include all electric homes with attached garages. Auto
exhaust may be the number #
1 cause of accidental CO poisoning in North America and has been reported
to be the cause of around 60%
of carbon monoxide alarm responses.
Just
notice how many people let their automobiles warm up inside garages with the
door open and for how long before they back out and close the door with their
automatic door control. CO gets
trapped inside the garage and can easily disperse into the rest of the building
through unseen but loose fitting construction connections (like wiring passes,
framing joints, ductwork seams, door jambs or framing and other areas).
Building pressure and temperature variations work as siphon points and air exchange locations.
Carbon monoxide in homes does not always come from traditional locations.
While
the industry has been targeting cracked heat exchangers as the leading menace in
the HVAC industry (almost exclusively without test instrument verification until
about 1985), those testing for CO indicate unvented, poorly
installed, unmaintained and misused gas cooking appliances are the 2nd leading
cause of CO alarm response, and may make up around 20%
of CO alarm call sources of CO generation.
The 3rd leading cause of CO alarm responses appear to be due
to vented atmospheric, natural drafting appliances that do not vent all the time.
This intermittent production of CO has tricked many
technicians and source investigations and may make up to 19% of
the CO alarm responses. Improperly
sized and installed vent systems, old vents in need of repair, and competing
building pressures contribute to this affect.
Additionally, the interactions of the draft hood of the appliance and
building exhaust sources may be the leading cause of draft failure and CO
production in these systems.
It should be noted
that cracked heat exchangers make up one of the smallest percentages (1/2 %) of
CO alarm response causes.
A furnace left in operation while a known crack exists should be thoroughly tested for complete combustion. Safe by-product generation and combustion gas venting helps ensure the system left in operation vents products of combustion out of the building and CO levels within those buildings remain within safe limits for infants, elderly, heart disease sufferers, asthmatics and others.
It
is always suggested to recommend the installation of a home CO alarm. It is not uncommon to find heating contractors and others,
after having notified the Authority
Having Jurisdiction about a cracked heat exchanger, to leave “loaner” CO
alarms and the furnace in operation until repair or replacement can occur.
Often times also, the consumer purchases the CO alarm or the contractor
builds that into the replacement bid as an option.
They may even give one as a free service.
What
type of CO alarm is being installed? Do
they have the same sensor capabilities as my test instrument?
When encountering households containing inhabitants
other than healthy young adults, please
advise using a more sensitive CO alarm system.
They may have a higher installation cost, but may prove to be more cost
effective and healthy for every body involved in the long term.
It must be noted that home carbon monoxide alarms
with digital displays have been reported in the field to have low CO PPM
displayed on the CO alarm but 0 PPM or trace measurements inside the building with hand-held, portable instruments.
When a hand held CO detecting instrument like the Monoxor IIâ
or CO Snifitâ is used, this discrepancy is often noted.
The
differences in sensitivity of the
types of sensors used are substantial at
low level accuracy. Alarm sensitivities, temperature restrictions, calibration
requirements, and sensitivity to low level, real time measurement for both types
of devices are different. Read the
instructions. The typical home
alarm, even those with a somewhat more sophisticated data logging and peak
measurement recorder do not protect all inhabitants from potentially harmful
concentrations of CO.
The comparatively inexpensive home alarms use sensor
technology not equipped to measure and display low level, short term
concentrations of CO (less than 60 PPM or 100 PPM usually).
The sensors used in Bacharach instruments are highly responsive to
immediately present low-level carbon monoxide molecules in the sampling
environment.
You
may find carbon monoxide levels in excess to outside levels and the alarm
has not sounded. You may not
find measurable CO inside a building where an alarm
has sounded. You may feel as if you are chasing ghosts when tracing
CO to its source or sources.
To chase this ghost, we’ve got to know what we’re chasing and how it is being detected.
The UL 2034
listing requirements for home alarms are based upon CO concentrations measured
in PPM and time of exposure.
Carbon
monoxide must be present in specific concentrations for specific times before
they will alarm.
This
time weighted measurement standard has gone through at least two revisions with
three versions (as of this 1/99 printing).
Oct. 99 revisions are already drafted.
As
a carbon monoxide source investigator, service technician, or other provider,
you may encounter any one of the following three listings.
1. April 30, 1992, UL 2034 listed CO alarms had to
measure and alarm when CO is:
15 PPM for 8 hour before alarming, or
100 PPM for no more than 90 minutes before alarming, or
200 PPM for no more than 35 minutes before alarming, or
400 PPM for no more than 15 minutes before alarming.
During this time (prior to 10/95), many communities
experienced an increased use of CO alarms by consumers, particularly Chicago.
First responders and Authorities of Jurisdiction had little experience
with carbon monoxide measurements at these “low” levels.
There were some suspicions of the accuracy of these alarms and many
encounters with CO alarm responses had the responders crying “False alarm!”
We must examine and remember that CO concentrations
outside of buildings in many urban areas will exceed 15 PPM for over 8 hours due
to automobile influences. We
must also remember the early CO alarm responders most likely were using CO test
instruments that auto-zeroed when turned on outside (inside or anywhere).
Likewise, first responders who had instruments that
allowed you to manually-zero your display were doing so inside or close to their
vehicles or outside of buildings in urban areas where back round readings of CO
were not zero.
Consequently,
many first responders or source investigators were starting with a false zero, thinking there was no CO in the
atmosphere they started in, when in reality, there was enough to perhaps trigger
the alarm. Their instruments might
not have shown but slight increases of CO upon entering those buildings, so they
thought the alarms were inaccurate or defective.
Additionally, some of the home alarms sounded off at 9 PPM or lower
before 8 hours. This
was and still is particularly troublesome for first responders in cities with
high pollution.
Another important thing to know about this generation of
CO detector is its’ response criteria for non-alarm status when selected
vapors and gases are present in specific concentrations. This Selectivity Test (Table 38.1 – Gas and vapor
concentrations) with these substances are intended to represent air contaminants
likely to be found in the vicinity of an installed detector.
Methane 500 PPM
Butane 300 PPM
Heptane 500 PPM
Ethyl Acetate 200 PPM
Isopropyl Alcohol 200 PPM
Carbon Dioxide
1000PPM
This low PPM
requirement for Carbon dioxide (CO2) concentrations may have been another major
contributing factor in how many nuisance alarms resulted in not finding CO and
nobody ever getting sick. First
responders and other CO source investigators most likely were not carrying any
type of CO2 measuring instruments that may have helped discover the cause of the
alarm.
It is not uncommon
to find CO2 levels in residential buildings much higher than 1000 PPM.
In our efforts to save energy we seal up our homes. Consequently, expired
breath alone from a family can be the main cause of excessive CO2 build-up over
1000 PPM.
Additionally, unvented combustion equipment, like gas
cooking ovens & burners, space heaters, fireplaces and others, dump
tremendous amounts of CO2 into the space. In
these circumstances, 2,000 to 3,000 PPM or higher of CO2 in air would not be
uncommon.
Because of the seemingly high number of false
alarms, much mistrust in this first generation of UL 2034 inexpensive
home CO alarms resulted.
Despite the number of false or what came to be termed ‘nuisance’ alarms,
many lives were saved the misery or death from CO poisoning.
Also, many
technicians, first responders, fuel suppliers, home inspectors and others
began to examine & question their own
practices and prejudices about carbon monoxide as well as codes, licensing,
education and other aspects of their profession.
It seemed that many of the rules of thumb pertaining to CO had come about
with little or no actual field-testing
being performed and were being passed around as hearsay.
Many who had been conducting CO and combustion testing
prior to the home alarm invasion knew it was a real problem in the field. Their
suspicions were that false alarms most
often meant inaccurate testing took place by personnel who did not fully
understand CO nor were they looking at the building as a system.
2.
After Oct. 1995, UL 2034 listed CO alarms had to measure and alarm when
CO is:
15 PPM for no less than 30 days, or
100 PPM for no more than 90 minutes before alarming, or
200 PPM for no more than 35 minutes before alarming, or
400 PPM for no more than 15 minutes before alarming, and
All alarms had
to have a reset button that
alarmed if 100 PPM or more is present for at least 6 minutes.
In essence, if the alarm sounded and the inhabitants of the building
showed no sign of CO poisoning (nausea, passing out, general weakness of the
body, etc.), they were instructed to enact the reset.
If it went off again, they were to vacate the building and call an
Authority. The selectivity Test
criteria remained at their same levels.
The Bacharach
Institute of Technical Training and their instructors had the opportunity to
conduct seminars all over North America through this revision.
It became obvious that lack of testing for CO and basic combustion
knowledge dominated the service industry. In
reference to all service professionals, a very small percentage of professionals
performed CO or combustion gas analysis.
Though that percentage is still small, it has grown significantly.
However, Bacharach’s instructors found that the more
testing conducted, the more knowledge gained
and the false and nuisance alarms were
diminishing by those who tested and measured.
Unfortunately and again in reference to the number of technicians in the
field, a small percentage of them test
for CO in every building and every combustion system they encounter.
3. Oct. 1, 1998, UL 2034 listed CO alarms must measure and alarm
when CO is:
30 PPM for 30 days
70 PPM for no more than 189 minutes before alarming (may alarm as early as 60 min.)
150 PPM for no more than 50 minutes before alarming (may alarm as early as 10 min.)
400 PPM for no more than 15 minutes before alarming (may alarm as early as 4 min.) and have a manual reset that will reenergize the alarm signal within 6 minutes if the CO concentration remains at 70 PPM or greater.
Another significant change to the 10/1/98 CO alarm listing is the addition in the instructions stating that individuals with medical problems may consider using warning devices which provide audible and visual signals for carbon monoxide concentrations under 30 PPM.
Before you make a recommendation concerning CO
alarms, it would be a good idea to know who
is in the building. Perhaps
a more sensitive alarm with lower CO concentration settings would be more
appropriate.
It must also be noted that Oct. 1, 1998 UL 2034
Residential CO Alarms must meet the
specificity test referencing non-alarm
status at specific concentrations of certain vapors and gases.
These concentrations include: Methane – 500 PPM, Butane – 300 PPM,
Heptane – 500 PPM, Ethyl acetate – 200 PPM, Isopropyl alcohol – 200 PPM
and Carbon dioxide (CO2) – 5,000 PPM.
Please note that the CO2 concentration was raised
dramatically. A 4,000 PPM increase
is significant and should result in less CO2 concentration caused alarms.
However, levels of CO2 in the 2,000 to 4,000 PPM range can be harmful to
even the healthiest of individuals and usually indicates lack of air change,
combustion gas spillage or both.
We may still encounter buildings where these
concentrations exceed these test limitations, particularly CO2 buildup from lack
of ventilation, improper use and placement of unvented space heating or cooking
equipment, backdrafting or spillage from vented combustion appliances or
systems. Many of the buildings we
enter have perhaps been over sealed to save energy.
Carbon dioxide (CO2) is also measured in PPM.
Excessive CO2 in air may cause illness symptoms similar to those of CO like drowsiness, sinus stuffiness or breathing difficulty. These symptoms can be compounded by warmer room temperatures. A CO2 and CO measurement upon entering buildings or rooms will give us immediate information about indoor air quality, safety and perhaps be vital to complete CO alarm investigations.
CO2 LEVELS OF COMFORT IN PARTS PER MILLION
Acceptable
levels
less than 600 PPM
Increased
complaints of stiffness and odors
600 to 1000 PPM
ASHRAE
and OSHA standards
1000 PPM
Increased
complaints of general drowsiness
1000 to 2500 PPM
Adverse
health effects
2500 to 5000 PPM
Maximum
allowable concentration for 8 hour period
5000 PPM
