OSHA Hazard Information Bulletins
Potential Carbon Dioxide (CO₂) Asphyxiation Hazard When Filling Stationary Low Pressure CO₂ Supply Systems

June 5, 1996

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 CO₂, 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 CO₂ 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 CO₂ delivery. This involved taking the hose from the truck and connecting it to the restaurant's bulk CO₂ 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 CO₂ 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 CO₂ 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) concentration.

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 individuals.

To minimize the development of hazardous conditions that may cause accidents or fatalities involving CO₂ 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 CO₂ 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 CO₂ 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 CO₂ 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 manufacturer's instructions.
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.

CGA G-6.5-1992, Standard for Small Stationary Low Pressure, Carbon Dioxide Supply Systems
CGA G-6.4-1992, Safe Transfer of Low Pressure Liquefied Carbon Dioxide in Cargo Tanks, Tank Cars, and Portable Containers
CGA G-6.3-1995, Carbon Dioxide Cylinder Filling and Handling Procedures
CGA G-6-1984, Carbon Dioxide
CGA G-6.2-1994, Commodity Specification for Carbon Dioxide
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 associations.