January 15, 2003
CO: The Silent Killer at Work
By Sean M. Alvarez, CSP
Referred to in many households
as "the silent killer", Carbon Monoxide (CO) is
not just a residential hazard. Your workplace could be at
risk as well. This month's OSH Basics familiarizes you with
a common workplace poisoning hazard which can easily be
WHAT IS CO?
CO is a common industrial hazard
resulting from the incomplete burning of natural gas and
any other material containing carbon such as gasoline, kerosene,
oil, propane, coal or wood.
During normal combustion, each
atom of carbon in the burning fuel joins with two atoms
of oxygen - forming a relatively harmless gas called carbon
dioxide. When there is insufficient oxygen to ensure complete
combustion of the fuel, each atom of carbon links up with
only one atom of oxygen - forming a colorless, odorless,
tasteless and poisonous gas called carbon monoxide.
While having no detectable odor,
CO readily mixes with other gases that do have an odor.
So, you can easily inhale carbon monoxide right along with
gases that you can smell and not even know that CO is present.
Although present in liquid form
under high pressure, carbon monoxide (CO) is most commonly
encountered as a gas. This gas is the leading cause of accidental
poisoning deaths in America, resulting in more than 1700
suicides and over 500 unintentional deaths every year in
the United States, according to the Journal of the American
Medical Association (JAMA). An additional 10,000 seek medical
HOW DOES CO HARM WORKERS?
Carbon monoxide is an asphyxiant
that exerts its toxic effects by combining with the hemoglobin
of the blood. This combination decreases the amount of oxygen
that can successfully combine with the hemoglobin and be
delivered to the tissues.
Simply put, carbon monoxide takes the place
of the oxygen, causing your tissues and organs to suffocate
and eventually stop working.
WHERE DOES CO COME FROM?
Just about any process or piece of equipment
using a flame can become a producer of CO. Forges, blast furnaces
and coke ovens all produce CO.
Even basic welding procedures generate the gas.
According to the Occupational Safety and Health Administration
(OSHA), welding and cutting may produce significant amounts
of carbon monoxide. In addition, welding operations that use
carbon dioxide as the inert gas shield may produce hazardous
concentrations of carbon monoxide in poorly ventilated areas.
Of all CO producers, one of the most commonly
overlooked in the workplace is the internal combustion engine.
In fact, many injuries and deaths occur from small engines
Many people using gasoline-powered tools such
as high-pressure washers, concrete cutting saws, power trowels,
floor buffers, welders, pumps, compressors, and generators
in buildings or semi-enclosed spaces have been poisoned by
The National Institute for Occupational Safety
and Health (NIOSH) provides these examples of such poisonings.
- A farm owner died of CO poisoning while using an 11-horsepower,
gasoline-powered pressure washer to clean his barn. He had
worked about 30 minutes before being overcome.
- A municipal employee at an indoor water treatment plant
lost consciousness while trying to exit from a 59,000-cubic-foot
room where he had been working with an 8-horse-power, gasoline-powered
pump. Doors adjacent to the work area were open while he
worked. His hospital diagnosis was CO poisoning.
- Five workers were treated for CO poisoning after using
two 8 horse-power, gasoline-powered, pressure washers in
a poorly ventilated underground parking garage.
- A plumber used a gasoline-powered concrete saw in a basement
with open doors and windows and a cooling fan. He experienced
a severe headache and dizziness and began to act in a paranoid
manner. His symptoms were related to CO poisoning.
HOW MUCH CO IS TOO MUCH?
According to 29 CFR, Table
Z-1, the current OSHA permissible exposure limit (PEL)
for carbon monoxide is 50 parts per million (ppm) parts of
air as an 8-hour time-weighted average (TWA) concentration.
The Consumer Product Safety Commission reports
that health effects from exposure to CO levels of approximately
1 to 70 ppm are uncertain, but most people will not experience
any symptoms. Some heart patients might experience an increase
in chest pain.
As CO levels increase and remain above 70 ppm,
symptoms may become more noticeable (headache, fatigue, nausea,
dizziness). Since symptoms of mild exposure to carbon monoxide
are similar to the flu, many victims of CO poisoning are misdiagnosed.
As CO levels increase above 150 to 200 ppm,
disorientation, muscle weakness, unconsciousness, and death
Additionally, pregnant women, unborn babies,
newborns, people with heart or respiratory problems, and the
elderly may be more vulnerable to CO poisoning.
HOW CAN I PREVENT CO EXPOSURE AT MY
Developing and implementing a Carbon Monoxide
Control Program at your workplace should help to minimize
- Conduct a workplace survey to identify all potential sources
of CO exposure.
- Inspect / establish periodic maintenance schedule and
equipment operating guides
- Educate workers about the sources and conditions that
may result in CO poisoning as well as the symptoms and control
of CO exposure.
- Conduct regular air monitoring of employees to determine
the extent of the hazard.
- Install Carbon Monoxide detectors and alarms in areas
where potential sources of CO exist.
Employers Should Also:
- NOT allow the use of or operate gasoline-powered engines
or tools inside buildings or in partially enclosed areas
unless gasoline engines can be located outside away from
- Substitute less hazardous equipment if possible. Use
equipment that allows for the placement of gasoline-powered
engines outdoors at a safe distance from air entering the
- Learn to recognize the symptoms and signs of CO overexposure:
headache, nausea, weakness, dizziness, visual disturbances,
changes in personality, and loss of consciousness. Any of
these symptoms and signs can occur within minutes of usage.
- Always place the pump and power unit of high-pressure
washers outdoors and away from air intakes so that engine
exhaust is not drawn indoors where the work is being done.
Run only the high-pressure wash line inside.
- Consider the use of tools powered by electricity or compressed
air if they are available and can be used safely.
- If compressed air is used, place the gasoline-powered
compressor outdoors and away from air intakes so that engine
exhaust is not drawn indoors where the work is being done.
- Use personal CO monitors where potential sources of CO
exist. These monitors should be equipped with audible alarms
to warn workers when CO concentrations are too high.
Equipment Users Should Also:
- Substitute less hazardous equipment whenever possible.
Use electric tools or tools with engines that are separate
from the tool and can be located outside and away from air
- Learn to recognize the warning symptoms of CO poisoning.
- If you have any symptoms, immediately turn off equipment
and go outdoors or to a place with uncontaminated air.
- Call 911 or another local emergency number for medical
attention or assistance if symptoms occur. Do NOT drive
a motor vehicle--get someone else to drive you to a health
- Stay away from the work area until the tool has been
deactivated and measured CO concentrations are below accepted
guidelines and standards.
- Watch coworkers for the signs of CO toxicity.
Each year, several thousands of people at home and at work
are poisoned by carbon monoxide. Do not be fooled into thinking
that the silent killer is only a residential hazard -- This
killer goes to work as well!
Below are some helpful links related to carbon monoxide:
Carbon Monoxide Poisoning from Small Gasoline-Powered Engines
and Tools [DHHS (NIOSH) Publication No. 96-118].
Carbon Monoxide Poisoning Fact Sheet (2 page PDF)
Your Family and Yourself from Carbon Monoxide Poisoning"
US EPA Indoor Air Quality Fact Sheet
for the Prevention of Carbon Monoxide (CO) Poisoning CDC
National Center for Environmental Health
Monoxide FAQ CDC National Center for Environmental Health
OSHA - Marine Terminals - Carbon
Monoxide - 1917.24
CITES TWO EMPLOYERS FOLLOWING JANUARY 3RD CARBON MONOXIDE
OVEREXPOSURES AT CHELSEA, MASS., MEAT WHOLESALER - OSHA
Regional News Release
to a request for information concerning the OSHA standard
for carbon monoxide -- OSHA Interpretation - 02/25/1988
September 20, 2002; 51(37);829-830 - Carbon-Monoxide Poisoning
Resulting from Exposure to Ski-Boat Exhaust --- Georgia, June
Monoxide Poisoning - an Invisible Danger on Houseboats:
Protect yourself and others from carbon monoxide poisoning
inside and outside houseboats.
Houseboat-Associated Carbon Monoxide Poisonings on Lake Powell
-- Arizona and Utah, 2000.MMWR
December 15, 2000;49(49):1105-8
Vehicle Emissions Policies and Practices and Declining US
Carbon Monoxide-Related Mortality
SAFETY - Carbon Monoxide: What is it and where does it come
from? National Ag Safety Database
Warns of Deadly Carbon Monoxide Hazard from Using Pressure
Washers Indoors CDC / NIOSH Alert - NASD
MONOXIDE - Farm Bureau Safety Program PDF
Monoxide and You - Montana State University Extension.
Publication date: February 1983
Carbon Monoxide Poisoning Attributed to Tractor Exhaust
Morbidity and Mortality Weekly Report (1997) PDF
Monoxide Poisoning in Enclosed and Semi-Enclosed Worksites
Hazard Alert Construction Safety Association of Ontario
Blaster Dies of Carbon Monoxide Poisoning
(Taken from Construction Safety Magazine, Construction Safety
Association of Ontario, Volume 10, Number 4, Winter 1999/200)
Against Carbon Monoxide Risk From Small Gasoline Engines Recommended
By NIOSH, Partners - NIOSH Update
Carbon Monoxide Kills Three Volunteer Firefighters Inside
Well in Pennsylvania - NIOSH News
Monoxide Questions and Answers - Consumer Product Safety
Commission - - CPSC Document #466
of CO with Asthma in Children - CO Headquarters
Monoxide Exposure: A Syndrome Induced by Chronic CO Poisoning
- CO Headquarters - list of symptoms
CO Poisoning Study of Meigs & Hughes, 1952 - CO Headquarters
Monoxide Kills Website - Campaign Web Site
CO Poisoning - CO Headquarters
Copyright © 2003 by WorkCare™ All
See you next month,