Educational Information about Carbon Monoxide

Educational Information about Carbon Monoxide
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TH-22 EDUCATIONAL INFORMATION ABOUT CARBON MONOXIDE
BACKGROUND
This technical information report provides educational material about carbon monoxide relative to boats and boating.
Carbon monoxide can accumulate in interior spaces and exterior areas. Carbon monoxide accumulation is affected by a multitude
of variables (e.g., boat geometry, hatch, window and door openings, ventilation openings, proximity to other structures, swim
platforms, canvas enclosures, location of exhaust outlets, vessel attitude, wind direction, boat speed, boat system maintenance,
etc.)
This technical information report discusses many of these variables and enables the reader to better understand some of the more
predictable effects. However, this report is limited in that it cannot cover all conceivable variables, and the reader is cautioned not
to rely exclusively on it to prevent the accumulation of carbon monoxide.
INTENT
The information in this technical information report concerns all boats.
REFERENCED ORGANIZATIONS
ABYC - American Boat & Yacht Council, 3069 Solomons Island Road, Edgewater, MD 21037. Phone (410) 956-1050. Fax:
(410) 956-2737. Web site: www.abycinc.org
DEFINITIONS - For the purpose of this technical information report, the following definitions apply.
Carbon Monoxide - A gas formed by the combination of one atom of carbon and one atom of oxygen. Chemists refer to it as CO
for its chemical formula, C for carbon and O for oxygen.
COHb (carboxyhemoglobin) - The molecule formed when CO, instead of oxygen, combines with blood.
Enclosed Accommodation Compartment - One contiguous space that contains the following:
a.
designated sleeping accommodations,
b.
a galley area with sink; and
c.
a head compartment.
NOTE: A cuddy intended for gear storage and open passenger cockpits, with or without canvas enclosures, are not
considered to be enclosed accommodation compartment(s).
PPM - Parts per million
PROPERTIES AND CHARACTERISTICS OF CARBON MONOXIDE
Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that weighs about the same as air. It cannot be expected to rise
or fall like some other gases because it will distribute itself throughout the space. Do not rely on the sense of smell or sight of
other gases to detect CO as it diffuses in the air much more rapidly than easily detectable vapors, (i.e., visible and aromatic
vapors).
WHAT MAKES CARBON MONOXIDE?
Carbon monoxide is produced any time a material containing carbon burns, such as gasoline, natural gas, oil, propane, coal, or
wood. Common sources of CO are internal combustion engines and open flame appliances such as
•
cooking ranges,
•
central heating plants,
•
space heaters,
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•
water heaters,
•
fireplaces, and
•
charcoal grills.
The carbon monoxide component of diesel exhaust is extremely low relative to the carbon monoxide level found in gasoline
engine exhaust.
HOW IS A PERSON AFFECTED BY CARBON MONOXIDE?
Carbon monoxide is absorbed by the lungs and reacts with blood hemoglobin to form carboxyhemoglobin, which reduces the
oxygen carrying capacity of the blood. The result is a lack of oxygen for the tissues with the subsequent tissue death and, if
exposure is prolonged, death of the individual. Altitude, certain health related problems, and age will increase the effects of CO.
Persons who smoke or are exposed to high concentrations of cigarette smoke, consume alcohol or have lung disorders or heart
problems are particularly susceptible to an increase in the effects from CO. However, all occupants’ health should be considered.
Physical exertion accelerates the rate at which the blood absorbs CO.
Carbon monoxide in high concentrations can be fatal in a matter of minutes. Lower concentrations must not be ignored because
the effects of exposure to CO are cumulative and can be just as lethal. (See Figure 1.)
FIGURE 1
CARBON MONOXIDE CONCENTRATION VS TIME
NOTE: Figure 1 shows the generally accepted curves of a person’s absorption rate of CO at various concentrations.
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Symptoms of CO Poisoning - The sequence of symptoms listed generally reflects the order of occurrence in most people;
however, there are many variables that affect this order of symptom manifestation. One or more of the following symptoms can
signal the adverse effect of CO accumulation:
1. watering and itchy eyes,
7. ringing in the ears,
13. nausea,
2. flushed appearance,
8. tightness across the chest,
14. dizziness,
3. throbbing temples,
9. headache,
15. fatigue,
4. inattentiveness,
10. drowsiness,
16. vomiting,
5. inability to think coherently,
11. incoherence,
17. collapse,
6. loss of physical
coordination,
12. slurred speech,
18. convulsions.
Emergency Treatment for CO Poisoning - CO toxicity is a life-threatening emergency that requires immediate action. The
following is a list of things that should be done if CO poisoning is suspected. Proceed with caution. The victim may be in an area
of high CO concentration.
•
Evaluate the situation and ventilate the area if possible,
•
Evacuate the area and move affected person(s) to a fresh air environment,
•
Observe the victim(s),
•
Administer oxygen, if available,
•
Contact medical help. If the victim is not breathing, perform rescue breathing or approved cardiopulmonary
resuscitation (CPR), as appropriate, until medical help arrives. Prompt action can make the difference between life and
death, and
•
Investigate source of CO and take corrective action.
MARINE CO DETECTION SYSTEMS
Even with the best of boat design and construction, and scrupulous attention to inspection, operation, and maintenance of boat
systems, hazardous levels of CO may, under certain conditions, be present in interior spaces and exterior areas. Vigilant
observation of passengers for CO sickness symptoms should be supplemented by a marine CO detection device in the
accommodation space. Detection devices should meet the requirements of ABYC A-24, Carbon Monoxide Detection Systems on
Boats.
NOTE: There are currently no known CO detectors available for permanent installation in exterior areas.
BOAT OPERATION
Don’t run engine(s) or auxiliary generator(s) on boats with enclosed accommodation compartments unless the boat is equipped
with a functioning marine carbon monoxide detector that complies with ABYC A-24, Carbon Monoxide Detection Systems on
Boats. There are currently no known CO detectors available for permanent installation in exterior areas.
Stationary Operation
A boat operator should be aware that dangerous concentrations of CO can accumulate when propulsion engines and/or an
auxiliary generator is operated while the boat is stationary, especially when rafted or moored in a confined area such as
boathouses, proximity to seawalls, or proximity to other boats. (See Figure 2.)
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FIGURE 2
THE EFFECT OF SEA WALLS AND OTHER CONFINED SPACES
This figure illustrates the effects of running engine or auxiliary generator in confined areas.
Keep engine room hatches and doors closed when operating engines, including the generator set. Before running generator set,
consult boat owner’s manual or boat manufacturer to determine if the blowers should be operated continuously.
Pay attention to prevailing conditions and provide for ventilation to induce fresh air and minimize exhaust re-entry. Orient boat to
enable the maximum dissipation of CO. Be aware that cockpit and deck drains can be a source of CO ingress into boats,
especially boats with cockpit or decks enclosed with canvas or permanent boat structures.
When the propulsion engine or generator is running, CO is produced and may remain in the vicinity of the exhaust outlet
(including underwater exhaust outlets such as sterndrives and outboards):
•
Do not occupy aft lounging area(s) or swim platform,
•
Do not swim under or around swim platform,
•
Do not swim in the vicinity of the exhaust outlet.
FIGURE 3
ACCUMULATION OF EXHAUST GASES AT THE SWIM PLATFORM
Since carbon monoxide production is greater when engines are cold versus when they are warm, a boat operator should minimize
the time spent on getting underway.
In order to minimize CO buildup, do not warm up or run propulsion engine(s) for extended periods while the vessel is stationary.
A boat operator should be aware that carbon monoxide is emitted from any boat’s exhaust. Operation, mooring, and anchoring in
an area where other boats' engines or generators are running may put your boat in an atmosphere containing CO, even if your
boat’s engine(s) is(are) not running. Boat operators need to be aware of the effect of their boat on other boats in the area. Of
prime concern is the operation of an auxiliary generator where boats are moored along side each other. Be aware of the effect
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your exhaust may have on other boats and be aware that the operation of other boats’ equipment may affect the carbon monoxide
concentration on your boat. (See Figure 4.)
FIGURE 4
THE EFFECT OF BOATS MOORED ALONG SIDE
Boats moored close together can affect each other.
Underway Operation
Do not sit on, occupy or hang on any stern appendages (e.g., swim platforms, boarding ladders, etc.) while underway. Do not
body surf, commonly known as “teak surfing” or “dragging”, etc. in the wake of the boat. Do not tow persons in close proximity
to the stern of the boat.
FIGURE 5
DANGEROUS ACTIVITY
Backdrafting (station wagon effect)
Backdrafting is caused by air movement over or around a boat creating a low pressure or suction area around the stern that can
increase CO level on the boat. Backdrafting can be affected by relative wind direction, boat speed, and boat trim angle. (See
Figure 6 for an illustration of airflow over a boat and behind its transom.) Under certain speed and operating conditions, the low
pressure area may form in other regions and permit carbon monoxide to enter the hull through openings that are not on the back
of the boat.
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FIGURE 6
BACKDRAFTING (STATION WAGON EFFECT)
This figure illustrates airflow over boat and behind the transom.
Other factors during boat operation which may affect carbon monoxide concentration include:
•
Adding or removing canvas may raise or lower CO levels. (See Figure 7.)
•
Intentional or unintentional excessive trim angle (e.g., high bow angle or excessive unequally distributed weight) may
raise the CO level and should be avoided. (See Figure 8.)
•
Opening and closing ports, hatches, doors, and windows may raise or lower CO levels on board a boat. When airflow is
moving forward inside the boat, CO may be entering the boat.
•
Operating a boat at slow speeds with a following wind should be avoided. Consider changing direction, adjusting
speed, or both. (See Figure 9.)
•
Be aware that cockpit and deck drains can be a source of CO ingress into boats, especially boats with cockpit or decks
enclosed with canvas or permanent boat structures.
FIGURE 7
THE EFFECT OF CANVAS CONFIGURATIONS
This figure illustrates desired airflow through the boat.
As shown in this figure, certain canvas configurations, such as side curtains, can increase backdrafting.
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FIGURE 8
INEFFICIENT TRIM ANGLES
FIGURE 9
OPERATING AT SLOW SPEED WITH A FOLLOWING WIND
Cabin Appliances - Boats having fuel-burning appliances in accommodation areas should be provided with adequate ventilation
and the appliance should be maintained to function properly.
Air Conditioning - Improper installation or lack of system maintenance may cause CO to be brought into the air-conditioned
spaces by the air conditioner. Be sure that the air handling ducts and plenums are sealed from the engine room(s).
Ventilation of Occupied Spaces - Occupied spaces need to be ventilated to introduce fresh air into the spaces. Ventilation
methods (e.g., windows, hatches, doors, and blowers) used to accomplish this may, under certain conditions, bring hazardous
levels of CO into the occupied spaces. Be aware of all prevailing conditions when using these ventilating methods.
Altitude and Sea Conditions - Operation at altitudes greater than 5,000 ft contributes to inefficient engine performance and may
require adjustments to ignition systems, fuel systems, or changing the propeller’s size or gear ratio. Failure to make adjustments
to ignition systems and/or fuel systems for altitude conditions may cause an increase in CO. Reduced power resulting from
increased altitude may require adjustments to propeller size. Heavy seas or out of trim conditions tend to load engines resulting in
reduced performance and increased CO production.
Portable Generator Sets - Do not use this equipment on boats. Gasoline powered portable generator sets produce CO. These sets
discharge their exhaust products in locations which can lead to an increase in the accumulation of carbon monoxide in the
occupied space.
MAINTENANCE
Engine Performance - Efficient engine performance is vital to minimizing CO production. The following items are those
considered to have the greatest effect on increased CO production:
Fuel that is contaminated, stale, or incorrect octane number
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Carburetors/Injectors
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Dirty or clogged flame arrester
•
Malfunctioning automatic choke plate or faulty adjustment of manual choke plate
•
Worn float needle valve and seat
•
High float level
•
Incorrect idle mixture adjustment
•
Dirty or worn injectors
Ignition System
•
Fouled or worn spark plugs
•
Worn points or incorrect gap on points
•
Shorted or opened circuit high tension spark plug cables
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Incorrect ignition timing
General
•
Worn piston rings and valves
•
Engine temperature - Cold running engines increase CO production. Engine cooling water system design and
selection of thermostat(s) are primary considerations affecting engine operating temperature. Generally, an engine
produces less CO if it operates at a relatively high temperature within manufacturer’s specifications.
•
Exhaust back-pressure - Certain alterations to the exhaust system may increase engine exhaust back pressure and
CO production
•
Restricted engine room or compartment ventilation
External Boat Conditions - Conditions that contribute to inefficient engine performance can include:
•
Fouled hull bottom
•
Damaged and fouled running gear (i.e., shaft, strut, propeller, rudder, and trim tabs)
•
Incorrect selection of propeller size
Exhaust System Integrity - Gas tight integrity of exhaust systems must be maintained to insure that leakage of CO within the boat
does not occur. Disassembly may be required to carry out a thorough inspection. Repair or replace components as indicated.
Inspect the following:
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Gaskets at cylinder head connection
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Castings and pipe fittings in the dry section
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All joints
•
Hoses
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Clamps
•
Mufflers and their drain plugs
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•
Thru-hull fittings
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Hangers and other supports
Ventilation Systems - Boats are equipped with ventilation systems to eliminate gasoline vapors. Blowers and fans may also be
provided for ventilation and to mitigate migration of CO into occupied compartments. Attention should be paid to the following:
•
Keeping ventilation intakes clear of debris
•
Replacing damaged hardware
•
Maintaining the integrity of the ducting material and its connections
•
Ensuring that position of ducting intake is not obstructed or restricted, collapsed, kinked, or crushed
•
Eliminating sags in ducting that can form a water trap
•
Checking hangers and other supports
•
Ensuring blower/fan is operational
•
Checking that airflow is present at discharge
•
Inspecting wiring to equipment
Bulkhead and Deck Integrity
•
Seal all visible openings (e.g., cracks, crevices, holes, including openings around wiring and piping runs) in bulkheads
and decks that separate machinery compartments from occupied compartments. These openings can permit migration
of CO vapors.
•
Check gaskets and sealing surfaces on hatches, doors, and access panels.
CO Detection Systems - Check system and its installation and maintain in accordance with the manufacturer’s instructions.
Air-conditioning Systems - These systems can be a source of CO ingress and migration of CO vapors.
•
Keep return air grilles and filters clean.
•
Seal bulkhead voids and openings at wiring and piping runs in return air ducting, plenums, and air handling equipment
enclosures, especially those adjacent to machinery compartment bulkheads.
•
Check that water traps and condensate drains are present. These may be in the form of a double loop in the drain line or
prefabricated p-traps. Any drain that discharges below the waterline when the boat is underway is sealed, by virtue of
its design, against CO intrusion.
Liquid Drains - Sink, shower, and condensate drains can be a source of CO ingress. Ensure that water traps are present and
contain fluid. These traps may be in the form of a double loop in the drain line or prefabricated p-traps. Any drain that terminates
below the waterline is, by virtue of its design, sealed against CO intrusion. Some drains that are below the waterline when the
boat is underway will be above the waterline when the boat is at rest. The location of drains, relative to the waterline, can be
affected by the dynamics of boat motion (i.e., underway or at rest).
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* * * * *
Origin and Development of ABYC TH-22, Educational Information about Carbon Monoxide
ABYC first published this report as T-22 in 1992 and updated it in 2000. This update is the work of the Fuel & Ventilation
Project Technical Committee.
* * * * *
ABYC technical board rules provide that all reports, including standards and technical information reports, are advisory only.
Their use is entirely voluntary. They are believed to represent, as of the date of publication, the consensus of knowledgeable
persons, currently active in the field of small craft, on performance objectives that contribute to small boat safety.
The American Boat & Yacht Council assumes no responsibility whatsoever for the use of, or failure to use, standards or
technical information reports promulgated by it, their adaptation to any processes of a user, or any consequences flowing
therefrom.
Prospective users of the standards and technical information reports are responsible for protecting themselves against liability for
infringement of patents.
The American Boat & Yacht Council standards and technical information reports are guides to achieving a specific level of
design or performance and are not intended to preclude attainment of desired results by other means.
© 2002 American Boat & Yacht Council, Inc.
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