VP of Engineering and Training Rick Reynolds discusses NFPA 12 compliance, LPCO2 systems, exposure limits and other CO2 safety concerns.
As a part of an effective fire prevention strategy, carbon dioxide, or CO2 has unique properties. It can reduce the actual fire by reducing the CO2 in the area by displacing oxygen. And it can reduce the actual fuel vapor in the air because when it discharges it displaces, and it has a molecular structure that contains the fuel vapor in the air. In particular, it has a cooling effect as well by atomizing or reducing the fuel vapor by reducing the fuel. It can remove the "fuel" side of the fire triangle, as well as remove the "heat" side by cooling. So CO2 is a very good firefighting agent and that's why it's so widely used and so readily available. Power generation customers still use it today and it's a very vital product in today's marketplace. However, whenever we talk about it in fire protection, though, there's a lot of safety elements that we must take into consideration.
How is CO2 stored and distributed?
Bulk CO2 is stored in red tanks as a liquid, and therefore must be conditioned and cooled. Well-designed systems use multiple piping networks coming off the red tanks along with selector valves which go out to individual hazards. The benefit of this type of low pressure system is that we can actually design the system where it can have "multiple shots" or "multiple zones of discharge." And another benefit is where we would just have one refueling truck come in, and that truck would back up and they bulk storage.
What are the risks of using Co2?
CO2 is a very economical system to use but with it also an exposure risk to individuals. When servicing systems, ORR Protection technicians put flagging tape around, and seal off the area to make sure everybody's protected when working in those environments. Even a minimum level of exposure or 2% or 3% dilution rate, individuals will start getting nauseated, dizzy and the possibility of passing out. At 8%, at 6%, individuals may begin to have tremors, headaches and other serious symptoms.
In a normal power generation setting, or lube oil skid, the percent of concentration that is required in a CO2 environment has the base concentration for all systems at 34% or higher based the hazard. An electrical hazard has a base concentration of 50%. The reason for that is the amount of density of hardware that's in the space, such as a lot of plastics.
At these high percentages, we run into serious CO2 safety considerations. At 15% you begin having tremors at one minute of concentration exposure. You become unconscious at 20% and 30% at only 30 seconds. In 1980, there were 89 deaths per year in the US alone from CO2 exposure. The Occupational Safety and Health Administration, estimates number of deaths because of confined space or CO2 deaths is still averaging around 90 per year.
The NFPA 12 (the CO2 code) went through significant changes in 2005, to address these safety concerns and institute safeguard to prevent injury and death. These changes were retroactive for all CO2 systems and ORR Protection stays on the cutting edge of these regulations and wants to be a safety and technical resource. If you have questions about CO2 safety or NFPA 12, ask one of our experts and ORR Protection would love to help.