Potential Dangers of Carbonated Beverage Systems
By Gary Scribner, National Board Member, National Board of Boiler & Pressure Vessel Inspectors
Recent incidents involving high concentrations of carbon dioxide (CO2) gases caused by improperly installed and poorly maintained carbonated beverage systems led to over a dozen hospitalizations in Pooler, Georgia, and Phoenix, Arizona, and identified the acute need to raise awareness of potential safety concerns related to these systems.
Currently, there are over 1,250,000 beverage systems that are filled on-site in the United States alone. Carbon dioxide liquid has an expansion rate of approximately 555%. Its vapor is 1.5 times heavier than air and displaces oxygen. The dangers associated with CO2 exposure are based on the concentration percentage and amount of time a person is exposed.
The Occupational Safety and Health Administration’s (OSHA) permissible exposure limit for an eight-hour time weighted average is only 0.5%. A 3% concentration results in deeper breathing, reduced hearing, headaches, increased heart rate, and has a short-term exposure limit of 15 minutes. Concentrations of 10% and greater lead to unconsciousness in under a minute, and death if no actions are taken.
Liquid carbon dioxide (CO2) was developed in the early 1900s specifically for making carbonated beverages. Historically, cylinders are filled with liquid CO2 at the distributors’ facilities and transported to businesses for use in carbonated beverage dispensing machines. This method still exists today and utilizes cylinders ranging from 10 to 100 pounds of liquid CO2. The cylinders are classified by the actual weight of liquid CO2 used to fill them.
These distribution systems have a good safety record since the cylinders are filled off-site and are designed for a much higher working pressure than the ones at which they normally operate. Problems associated with this process typically result from improper handling and storage of the cylinders, as well as lack of employee knowledge about the potential dangers of CO2 systems. These cylinders fall within Department of Transportation (DOT) regulations since they are transported via roads and highways. Other than DOT regulations, few regulations exist for this type of process.
CYLINDERS FILLED ON LOCATION
Approximately 20 years ago the carbonated beverage industry developed a system to fill cylinders on-site at businesses that use carbonated dispensing machines, giving CO2 distributors/suppliers the capability to service more customers less often by filling the larger storage vessels using tank trucks. Today, almost every gasoline station, convenience store, bar, and restaurant has a carbonated beverage system. Cylinders used in this system contain a much larger volume of liquid CO2 and can range from 200 pounds to 750 pounds of liquid CO2. The size of the storage cylinders is based on both the volume of beverages served at the location and the delivery frequency of the distributor/supplier.
Cylinders which are not transported are not DOT-regulated or -certified cylinders, and are designed for a working pressure from 300 psi to 350 psi and are double-walled. The inner vessel is the storage area while the outer area has a coil and is under a vacuum to facilitate the change of state from liquid to gas.
Most systems using these tanks utilize a fill box that is installed on the outside of the building. It should be noted that in some instances the owner of the building will not permit a fill box to be installed. In these cases, the distributor /supplier either disconnects the piping from the CO2 cylinder or brings the fill hose inside the business to fill the cylinder. If a fill box exists, the box is fitted with a fill connection and a vent or relief connection, both of which must be properly piped out of the storage cylinder.
The internal pressure of these CO2 cylinders varies based on the amount of liquid, ambient temperature, the vacuum in the outer vessel, and the volume of CO2 changing state at that time. Cylinders may reach the maximum working pressure when being filled or immediately after high-usage times resulting in the excess pressure being vented through the safety relief circuit of the system. This creates the highest potential for risk of CO2 to be released from the cylinder. Most cylinder manufacturers are very explicit regarding the installation instructions for these systems and require the vent or relief circuits to be piped to a fill box installed at a safe point of discharge outside the building. Additionally, the location of the vent or fill box should not be below grade or in any enclosed area outside the building. Several incidents involving injury and even death have occurred when the vent circuit was not in a free air flow area outside the building.
These systems are seldom regulated by local jurisdictions. Lack of knowledge of how the systems function, lack of proper detection equipment, and change in environment between the time of incident and an investigation have led to the lack of reporting and/or misreporting of incidents and near misses.
The following are incidents directly related to carbonated beverage system malfunctions due to: improper installation and/or maintenance, renovation to rooms or areas where the systems were installed without an engineering evaluation of the effect on the systems, and/or lack of knowledge about the dangers of CO2 gas:
September 2011 – Ten people hospitalized, including two firefighters, and one fatality at a fast food restaurant in Pooler, Georgia.
June 2011 – Evacuation of a fast food restaurant in Dorchester, United Kingdom.
May 2011 – Three hospitalized, including two firefighters, at a fast food restaurant in Phoenix, Arizona.
May 2010 – Evacuation of a movie theater in Des Moines, Iowa.
July 2008 – Two hospitalized from an incident in a bar in Benson, Nebraska.
April 2008 – One fatality in a hotel in Victoria, Australia.
August 2007 – Fatality of a waiter at a restaurant in Coronado, California (DOT cylinder).
January 2005 – Two fatalities, employee and delivery driver, outside a fast food restaurant in Sanford, Florida.
March 1998 – Two hospitalized and two treated at the scene at a fast food restaurant in the US. Location unknown.
996 – Fatality of a delivery driver outside a restaurant in Cincinnati, Ohio.
Some jurisdictions do require inspection of beverage systems that are filled on-site. Initial inspections revealed a violation rate of over 25% related to the safety/vent circuit installation statewide, with some isolated communities having close to a 100% violation rate.
Local considerations should be given as a means to detect carbon dioxide in businesses or places of public assembly that utilize bulk CO2 systems, and can include:
Prohibiting CO2 systems of any type from being installed below grade.
Prohibiting the filling of storage tanks inside a business and/or disconnecting any system piping to facilitate filling.
Mandating posted signage warning employees, customers, and first responders of the utilization of CO2 and the potential risk and symptoms associated with carbon dioxide exposure.
Additional consideration should be given to CO2 awareness training for emergency responders, businesses, and places of public assembly utilizing CO2, as well as obtaining CO2 detection equipment for first responders.
The public and jurisdictional authorities should be aware that carbon dioxide exists and has many uses within industry, especially the food industry. The OSHA incident reporting system has 20 pages of incidents and fatalities involving CO2 exposure. Additionally, carbon dioxide systems (almost identical to the carbonated beverage systems) have recently been discovered being utilized with large swimming pools to control pH and is now being used as a refrigerant in what are advertised as “green systems.”
Awareness and inspection of carbonated beverage systems is the key to ensuring the safety of emergency responders and the public.
For further information regarding CO2 systems, please contact the chief boiler inspector of your jurisdiction.
Gary is Deputy Chief of Broiler & Pressure Vessel Safety Unit of the Missouri Division of Fire Safety. This article was originally printed in the Summer 2012 National Board Bulletin of Boiler and Pressure Vessel Inspectors.