Which statement is true about the notation 4B195?

• A. 195 psi is the normal operating pressure
• B. 195 psi is the hydrostatic test pressure
• C. 195 psi is the minimum safe pressure
• D. 195 psi is unrelated to pressure

Answer: (A)

The number at the end of the notation is the operating pressure the extinguisher is designed to maintain when it’s charged. In this case, 195 psi is the pressure the device is intended to operate at, so it represents the normal working pressure you’d expect to see on the gauge when the extinguisher is ready for use.

Hydrostatic test pressure is a separate requirement used during maintenance to verify the cylinder’s integrity. It’s a higher pressure applied only during testing, not the pressure the extinguisher is meant to operate at day to day, so it isn’t what the notation indicates.

The minimum safe pressure isn’t specified by this label either; there’s a different tolerance range or low-pressure limit defined by the manufacturer and standards, and if the gauge reads below that, maintenance is required.

So the statement that 195 psi is the normal operating pressure matches what the notation conveys.