OSHA Hazard Information Bulletins
June 5, 1996
Directorate of Technical Support
||Hazard Information Bulletin(1): Potential Carbon
Dioxide (CO(2)) Asphyxiation Hazard When Filling
Stationary Low Pressure CO(2) Supply Systems
FOOTNOTE(1) The Directorate of Technical Support issues Hazard
Information Bulletins (HIBs) in accordance with OSHA Instruction CPL 2.65
to provide relevant information regarding unrecognized or misunderstood
health hazards, inadequacies of materials, devices, techniques, and safety
engineering controls. HIBs are initiated based on information provided by
the field staff, studies, reports and concerns expressed by safety and health
professionals, employers, and the public. Information is compiled based on a
thorough evaluation of available facts, literature and in coordination with
appropriate parties. HIBs are used as an outreach tool for accident
A potential asphyxiation hazard exists when carbon dioxide is dispensed from
tank cars (rail cars), cargo tanks (tank trucks and trailers), and portable
containers to stationary, low pressure, carbon dioxide supply systems at
consumer sites. These systems are used for supplying carbon dioxide gas at
beverage dispensing sites, greenhouses, welding fabricators, and in other
applications. High concentrations of CO(2), which displaces oxygen, can
result in death in less than 15 minutes.
The Cincinnati, Ohio Area Office recently brought to our attention the case
of a delivery driver who succumbed to carbon dioxide asphyxiation while
dispensing CO(2) from his tractor-trailer. The driver, working for a
restaurant supply company, pulled his trailer to the back of a restaurant at
1:30 a.m. to make deliveries of carbon dioxide and other supplies. This was
a routine delivery for this driver as he made regular deliveries to this
restaurant every five days at this time of night. The driver checked in with
restaurant management and then proceeded to make his CO(2) delivery. This
involved taking the hose from the truck and connecting it to the restaurant's
bulk CO(2) system through a fill station located on the wall, below ground
level, just outside the door to the basement.
After one-half hour, restaurant employees started to look for the driver and
found him unconscious and lying face up at the bottom of the stairwell; they
immediately called 911. The paramedical team had to use SCBAs to remove the
victim from the stairwell. The paramedics were unable to revive him and he
was declared dead at the local hospital.
The fill station was located in the below-ground stairwell, with a partial
covering over the top of the doorway. The stairway and basement doorway were
completely below grade.
The accident apparently resulted from a CO(2) leak caused by an incomplete
seal of the delivery mechanism where the hose from the truck's bulk system
fastened to the fill connection (a fixed brass fitting) at the outside wall
of the restaurant. This condition was exacerbated by the fact that the below
grade location allowed the CO(2) to accumulate without dissipation.
Carbon dioxide is a colorless, odorless gas and should be treated as a
material with poor warning properties. It is denser than air and high
concentrations can persist in open pits and other areas below grade. The
current OSHA standard is 5000 ppm as an 8-hour time-weighted average (TWA)
Gaseous carbon dioxide is an asphyxiant. Concentrations of 10% (100,000
ppm) or more can produce unconsciousness or death. Lower concentrations may
cause headache, sweating, rapid breathing, increased heartbeat, shortness of
breath, dizziness, mental depression, visual disturbances or shaking. The
seriousness of the latter symptoms is dependent on the concentration of
carbon dioxide and the length of time the individual is exposed. The
response to carbon dioxide inhalation varies greatly even in healthy normal
To minimize the development of hazardous conditions that may cause accidents
or fatalities involving CO(2) intoxication:
1. Personnel handling liquid carbon dioxide should be thoroughly familiar
with the hazards associated with this product.
2. When new carbon dioxide receptacles are installed (as in new
construction or remodeling), they should be installed at ground level in an
open area. If feasible, it is recommended that existing CO(2) fill stations
be relocated to above grade locations in order to prevent dangerous
accumulations of CO(2) in below grade areas. Where fill stations are located
in confined spaces, the requirements of the permit in the required confined
space standard must be followed.
3. Even when carbon dioxide is delivered in enclosed areas or below grade
locations that are not confined spaces, it is necessary to ventilate such
areas adequately to maintain a safe working environment for personnel.
Since gaseous carbon dioxide is 1.5 times denser than air, it will be found in
greater concentrations at low levels. Therefore, ventilation systems should
be designed to exhaust from the lowest level and allow make-up air to enter
at a higher point.
4. Develop and implement a procedure to monitor the atmosphere for CO(2)
and provide local ventilation where levels may exceed the PEL. Do not
depend on measuring the oxygen content of the air because elevated levels of
carbon dioxide can be toxic, even with adequate oxygen for life support.
5. We recommend that appropriate warning signs be affixed outside of those
areas where high concentrations of carbon dioxide gas can accumulate.
Recommended language is shown below:
CAUTION - CARBON DIOXIDE GAS
Ventilate the Area.
A High CO(2) Gas Concentration
May Occur in this Area
And May Cause Suffocation.
6. Establish a procedure for inspection and maintenance, at regular
intervals, of all piping tubing, hoses, and fittings. The entire system
should be maintained by qualified personnel in accordance with the
7. Proper lighting may be important to enable workers to use these systems safely.
8. For further information on stationary low pressure, carbon dioxide
supply systems and related topics, the following Compressed Gas Association,
Inc. (CGA) pamphlets should be consulted. These pamphlets are designed to
assist personnel involved in transferring liquid carbon dioxide, designers,
engineers, safety and training personnel, distributors, restaurant personnel,
other users, inspectors and all interested parties.
|| Standard for Small Stationary Low
Pressure, Carbon Dioxide Supply
| CGA G-6.4-1992,
|| Safe Transfer of Low Pressure
Liquefied Carbon Dioxide in Cargo
Tanks, Tank Cars, and Portable
||Carbon Dioxide Cylinder Filling and
| CGA G-6-1984,
|| Carbon Dioxide
| CGA G-6.2-1994,
|| Commodity Specification for Carbon
| CGA G-6.6-1993,
|| Standard for Elastomer-Type Carbon
Dioxide Bulk Transfer Hose
Please distribute this bulletin to all Area Offices, State Plan States,
Consultation Project Officers, and appropriate local labor and industrial
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