Study Provokes Stern Warning
Chances are, if you operate a gasoline-powered express cruiser
with the canvas enclosure in place, dangerously high levels
of carbon monoxide (CO) could build up at the stern, the swim
platform and even in the cockpit and cabin.
out of 10 express cruisers evaluated during normal operating
conditions in an interagency survey by the National Institute
of Occupational Safety and Health (NIOSH) and the U.S. Coast
Guard, the “station wagon” effect
was found to generate hazardous concentrations of CO in areas
where passengers congregate.
the Coast Guard have teamed up before to study CO exposure
following a number of highly publicized CO deaths in the
late 1990s. The latest study, conducted during 2005 and 2006
at locations in Florida, North Carolina and New Jersey, was
designed to help the Coast Guard better understand how CO
poisonings may occur on express cruisers, identify the most
hazardous conditions and to begin the process of identifying
ways to mitigate CO exposures.
Express cruisers generally have a raised bridge deck that
houses the helm station, with a windshield and canvas bimini
top or hardtop that extends over the bridge and cockpit to
provide protection from the elements. They also feature extensive
enclosed accommodations below decks.
The boats evaluated in the survey were brand new gas-powered
cruisers ranging in size from 30 to 42 feet. and built by several
different manufacturers. The report does not identify boat
makes and models. All boats had standard factory power, with
inboard engines made by Volvo Penta, Crusader or Mercury Marine
and most had stern drive units. In addition, all boats were
equipped with gasoline-powered generators manufactured by Kohler.
Neither the engines nor the generators were found to be faulty.
show that in three cases CO levels in the aft parts of the
boats exceeded 1,100 parts per million (ppm). Six others
tested out at over 100 ppm to as high as 658 ppm. According
to the study report, only one vessel, which was equipped
with a combined exhaust system showed “concentrations
at the stern consistently below the NIOSH ceiling limit of
200 ppm with the canvas enclosed.”
To put this in perspective, the EPA standard for maximum
CO exposure is no more than nine ppm during an eight-hour period
and 35 ppm for a one-hour average. Data compiled by the Coast
Guard, NIOSH, the Dept of Interior and the National Park Service
show that CO has caused 113 deaths and 458 reported poisonings
on or near recreational boats in the past 20 years.
“The CO levels did not surprise me, I have seen similar
(and higher) levels in several of the studies I have participated
in and read,” American Boat & Yacht Council Technical
Director John Adey told BoatU.S.
the CO levels are so high, why aren’t more
people being adversely affected? “I believe the issue
here is exposure length,” Adey answered. In the tested
boats, CO levels varied with changes in boat speed, wind speed
and direction and configuration of the canvas cover. So, in
real-life conditions, passengers may experience only momentary
exposure, which could result in symptoms similar to seasickness.
Adey said ABYC technical committees concerned with CO education
and boat design and construction are poised to review the study.
For years, the CO problem has been the focus of joint efforts
by the Coast Guard and ABYC. However, federal regulations administered
by the Coast Guard do not address design and construction issues
that involve CO in exterior settings.
Guard tests were conducted at the dock with engines running and
while underway at speeds ranging from 5 to 25 miles per hour,
with and without the generators running. The boats’ canopies
were in various configurations — open, partially open
and closed — for every phase of the tests.
to the express cruisers study, “When the
canvas is deployed and the boat is underway, CO concentrations
exceeded the ‘immediately dangerous to life and health’ level
near the swim platform for many of the evaluated boats.” Travel
speed, wind direction, presence or lack of forward- facing
ventilation, canvas design, hull shape, exhaust system configuration
and proximity to structures like docks and other boats are
some of the factors that influence CO build-up.
CO is produced when fuels such as gasoline, wood and propane
are burned. In comparison to gasoline exhaust, the CO component
of diesel exhaust is extremely low, so diesel engines and generators
are not considered a serious risk. CO is absorbed by the lungs
and limits the ability of blood to carry oxygen. Depending
on concentrations, exposure time and the health and age of
victims, CO can cause unconsciousness, collapse and even death
in only a matter of minutes. Low-level exposure can cause symptoms
similar to seasickness, so many boaters may not suspect CO
is the culprit when a passenger falls ill.
of the NIOSH/Coast Guard test results shows the following:
the canvas was in place, CO concentrations on the
test boats immediately reached levels deemed by NIOSH to
dangerous to life and health.” Peak
CO concentrations “often exceeded 1,100 ppm,
while average CO concentrations were well over 100
ppm in the stern.” On
at least one boat, however, CO levels remained at about
1,000 with or without the canvas in place.
configuration significantly affected CO concentrations
in the cockpit area.
combination of travel at low speeds, into the wind with
the canvas fully deployed and no forward hatches opened
maximized the station wagon effect, pulling significant amounts
of CO into the cockpit.
test boats equipped with a combined exhaust system exiting
at the sides and underwater exhibited about 40% lower CO
concentrations than vessels equipped with exhaust systems
that were at or above the water line. The system is engineered
to release all the exhaust at the surface through the sides
of the vessel when the engine is idling or the rpm level
is below 1500. At levels over 1500 rpm, a pressure release
mechanism on the lower part of the hull is activated that
releases most of the exhaust underwater. Researchers found
that exhaust gases released underwater take longer to reach
the surface and are broken up by prop turbulence, reducing
CO concentrations close to the boats.
to popular wisdom, operating the boat at higher speeds
was no guarantee of adequate ventilation when the canvas
was in place. Researchers found the CO was still present.
bulkheads between engine compartments and living spaces
were adequately sealed on all boats tested. Seepage of
exhaust through bulkhead seams was eliminated as a source
for CO that migrated into cabins.
CO warning labels do not contain adequate information
to properly warn about potential hazards and preventive
or corrective measures to prevent CO poisonings.
cabin doors were closed while test boats were underway,
the cabins were under negative pressure when air conditioners
were running. This can lead to CO intrusion if cabin doors
or bulkheads do not seal properly.
a number of the boats tested, openings in the hull for
generator exhaust lines were located adjacent to engine
compartment air intake ports, in effect, allowing the
intake to “inhale” the generator’s
report points out that, unlike automobile engines, which
are equipped with catalytic converters that remove many
air pollutants and substantially reduce CO emissions, catalytic
converters for marine engines are still cutting edge. Indmar
Products Co., Inc., recently introduced the first production
catalytic converter system, EXT/CAT, which will be standard
equipment on 2007 Indmar 5.7L EFI inboards. An Indmar spokesman
told BoatU.S. the company is not planning to sell EXT/CAT
technology to other engine makers.
the current study provides insight into how CO poisonings
may occur on express cruisers, more research is needed to “evaluate
different options to reduce onboard CO exposures,” according
to NIOSH engineer Alberto Garcia.
“We conducted some additional tests to evaluate the
effects of blowers and fans to ventilate cockpits and cabins
on these vessels,” said Garcia. “However, the data
is non-conclusive and we are still looking into other options
to reduce or mitigate onboard CO concentrations.”
is very difficult to draw conclusions from a single test,
for one boat, under the evaluated conditions,” Garcia
Cappel, chief of the Coast Guard’s recreational
boating product assurance branch, agreed. “The preliminary
results from the follow-on testing showed that the [preventive]
measures taken were not 100% effective. The data collected
need to be analyzed to determine just how effective they were.
awareness is crucial. “Initial symptoms of CO
intoxication can be easily confused by what is commonly known
as ‘sea sickness,’ Garcia pointed out. There is
a lack of education and lack of reporting that makes it hard
to identify the extent of the problem. Education, training
and symptom recognition are important in identifying and preventing
Boat owners need to be pro-active in minimizing the CO dangers
on board. The first line of defense is to install functional
carbon monoxide detectors in all enclosed living spaces. And,
know where engine and generator exhaust outlets are located
and keep everyone away from these areas. Always maintain adequate
forward-facing ventilation when the engine or generator is
running and the canvas enclosure is in place. As an added precaution,
leave the canvas slightly open to increase air flow. Finally,
never let anyone sit, teak surf, or hang on the back deck or
swim platform while the engines and generators are running.
Teak surfing is NEVER a safe activity.
more about the CO threat, visit the Coast Guard Web site,
uscgboating.org, or call 800-368-5647 to obtain a copy of
the Coast Guard’s brochure, “Carbon Monoxide
Poisoning: What You Can’t See...”
Additional CO information is available at the BoatU.S. Foundation
Web site, www.boatus.com/foundation/grants/carbon_monoxide.htm.
Copyright BoatU.S. Magazine, Nov 2006