electrical equipment. The nondamaging quality of this agent makes it useful as an extinguishing agent for computer rooms and computer tape vaults.

There are two general types of carbon dioxide extinguishing systems, high pressure and low pressure.

High-Pressure Systems

In the high-pressure system, high-pressure cylinders are used to store liquid carbon dioxide at ambient temperatures (fig. 8-30). Normal cylinder pressure is nominally 600 psi and varies with the ambient temperature of the storage area. Storage area ambient temperatures should not exceed 130F or be less than 32F. For safety purposes, high-pressure cylinders have a frangible disk that will burst at 3,000 psi to prevent cylinder rupture as a result of overpressurization.

Low-Pressure Systems

Low-pressure systems have a pressure vessel maintained at 0F by insulation and refrigeration equipment (fig. 8-31). At this temperature, the pressure in the container is approximately 300 psi. Because the container is kept at a low temperature, the container can be filled to 90 to 95 percent of capacity. For safety purposes a relief

Figure 8-31. - Refrigerated low-pressure C02storage tank.