WorkSafe Bulletin
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Hazards of carbon monoxide in sports arenas
In two separate incidents, arenas were evacuated after children were exposed to carbon monoxide while skating.
At one arena, children began to feel ill and two children fell into a state of semi-consciousness. During the
emergency evacuation, firefighters took air samples and found carbon monoxide levels as high as 264 parts
per million. The suspected source of the carbon monoxide is an ice resurfacer that had mechanical problems.
In the second incident, several minor-league hockey players were taken to hospital with signs and symptoms
of carbon monoxide poisoning. A scissor lift used earlier in the day inside the arena is the suspected source.
What is carbon monoxide?
Exposure limits for carbon monoxide
Carbon monoxide (CO) is a colourless, odourless,
tasteless gas that is produced during the combustion
of fuels such as gasoline, diesel, and propane. It
combines with the air and enters the lungs when
someone breathes.
The Workers’ Compensation Board of B.C. sets the
following exposure limits for CO:
Symptoms of carbon monoxide
poisoning
Victims of CO poisoning cannot see or smell this
gas so they don’t realize they are in danger. CO
combines with hemoglobin in the red blood cells,
taking the place of oxygen. It reduces the oxygen
carried in the blood, and the following symptoms
begin to appear:
• Headache
• Watery or itchy eyes
• Rosy cheeks
• Nausea
• Weakness
• Dizziness
• 25 ppm (parts per million) as an 8-hour
exposure limit
• 100 ppm as a short-term exposure limit
Causes of carbon monoxide build-up
CO can build up in any poorly ventilated space
where the gases produced by combustion can collect.
In an arena, this includes gas- or propane-powered
equipment such as ice-resurfacing machines,
edgers, and scissor lifts. CO tends to collect closer
to the cold surface of the ice. For example, some
air samples tested after an arena was ventilated
have shown levels as high as 130 ppm about
30 centimetres (1 foot) from the ice surface.
A high enough level of CO can eventually lead to
unconsciousness, convulsions, heart damage, brain
injury, or death.
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Workers’ Compensation Board of B.C.
Detecting the presence of
carbon monoxide
Mobile equipment with internal combustion
engines used inside an arena poses a risk of CO
overexposure. In such situations, the Occupational
Health and Safety Regulation requires air sampling.
Reducing emissions
The best way to prevent CO emissions is to reduce
them at the source.
Personal monitors
Monitors worn by mobile equipment operators are
a practical option. Personal monitors continuously
monitor for exhaust emissions in the surrounding
air and sound an alarm when the levels detected are
too high. Operators of ice resurfacers and edgers are
close to the source of exhaust from the equipment
as well as close to the surface where CO is likely
to accumulate. If the equipment is producing high
levels of CO, the operator can take immediate action
and shut down the equipment causing the high
levels of CO. If a personal CO monitor is used, the
equipment operator must be trained in its use.
Fixed monitors
Fixed CO monitors continuously monitor the
surrounding air and sound an alarm if the gas is
building up to a dangerous concentration. The
CO monitor could be connected to the ventilation
system so that a ventilation fan would turn on if the
CO reading reached a certain level.
CO will be less concentrated as it moves away from
the equipment toward the fixed monitor. Therefore,
fixed monitors alone will not provide enough
warning for the equipment operators, who are
located near the source of the CO. The best option
may be to use fixed monitors in addition to personal
monitors worn by mobile equipment operators.
Since CO tends to collect in layers, fixed monitors
must be used appropriately. They need to be placed
close to the area of highest concentration but not
where they might be damaged. Since the highest
CO concentration is near the surface of the ice, a
fixed monitor should be located about 75–90 cm
(30–36 inches) above the ice surface. To protect the
monitor from being hit by people or hockey pucks,
attach the monitor on the far side of the boards, with
a hole drilled through the board to allow the monitor
to detect CO levels from the rink side. Even in that
location, damage is possible and monitors must be
checked regularly to ensure they are working.
Page 2 of 3
Ice edgers and other equipment powered by an
internal combustion engine can be a source of poor
air quality in arenas.
Proper maintenance of mobile equipment
Proper maintenance of mobile equipment powered
by gas or propane will minimize air contaminants
in the exhaust. These machines must be regularly
serviced by trained workers following the
manufacturer’s instructions. In some arenas,
operators without maintenance qualifications are
servicing the machines and adjusting the air/fuel
mix, resulting in increased air contaminants such
as CO.
The maintenance schedule should include regular
exhaust gas analysis testing. Engines cannot
be tuned just to minimize CO in the exhaust or
other problems may arise. For example, high
concentrations of nitrogen dioxide have been
reported in arenas using propane-powered ice
resurfacers that are not equipped with a 3-way
catalytic converter.
Maintenance should also include a catalyst efficiency
monitor. This monitor tests for the hydrocarbon
conversion efficiency of the catalyst by comparing
the upstream heated oxygen sensor with the
downstream sensor.
Operating procedures
It is recommended that ice resurfacers warm up for
two minutes outside the arena to reduce emissions
inside the arena. The catalytic converter is not
effective until it is warmed up.
Building ventilation
Ensure the ventilation is operating to the design
specifications. The building must have general
exhaust ventilation that is used when workers
are operating mobile equipment that produces
emissions. If the machines have catalytic converters
and are well maintained, the following exhaust
ventilation will usually control the emissions from
the two main sources of CO:
• Ice resurfacer, 3000 cfm (cubic feet per minute)
• Ice edger, 1500 cfm
How to assist someone with
carbon monoxide poisoning
All mobile equipment with internal combustion engines
used inside arenas must be properly maintained to
prevent overexposure to air contaminants.
Type of equipment
Some older engines without catalytic converters
produce more emissions. Ice resurfacers that control
the air/fuel mixture with computers and have a
3-way catalytic converter will control both CO and
nitrogen dioxide emissions. Consider replacing old
equipment or retrofitting emission control devices.
Installing an oxygen sensor in the exhaust manifold
before the catalytic converter and having a feedback
control system will help control emissions.
The exhaust stack for the ice resurfacer should be
directed vertically to assist in pushing the exhaust
gases away from the ice surface.
Electric equipment does not produce these exhaust
gases, so consider whether an electric edger or
resurfacer is practical for the size of arena.
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Ensure that all workers know the hazard of
CO build-up and can recognize the signs and
symptoms of CO poisoning. Watch for symptoms
such as headaches, dizziness, nausea, or mental
confusion. Take action immediately if you suspect
CO poisoning. Quick action can mean the difference
between life and death.
1. Move the person to fresh air.
2. Give the person oxygen, if available.
3. Call for medical help.
4. If the person is not breathing, perform artificial
respiration or CPR until medical help arrives.
5. Ventilate the area thoroughly.
6. Determine the source of the CO and eliminate it.
If a person is unconscious as a result of CO exposure,
the air may be a risk to the life of would-be rescuers.
Call for help by those trained and equipped to rescue
someone in an oxygen-deficient atmosphere.
WorkSafeBC Prevention Information Line: 604 276-3100 or toll-free 1 888 621-SAFE (7233)
WS 06-01