Question 26 QMED05 - Machinist-Pump Technician

The Correct Answer is B **Explanation for B (pull pin and open valve):** Option B describes the standard operating procedure for a carbon dioxide ($\text{CO}_2$) extinguisher featuring the common "squeeze grip" or "horn-and-valve" type of head shown in typical illustrations (like SF-0008, which usually depicts a safety pin and a trigger valve). 1. **Pull Pin:** The safety pin must be pulled (removed) first. The pin is a locking mechanism that prevents the trigger (valve) from being accidentally depressed (opened) while the extinguisher is being handled or stored. 2. **Open Valve (Squeeze Trigger):** Once the pin is removed, the user must squeeze the operating lever (trigger valve) to pierce the internal seal and release the pressurized $\text{CO}_2$ agent through the horn. **Why the other options are incorrect:** * **A) open valve, pull pin, and pull up on release lever:** This is incorrect. The valve cannot be fully opened until the safety pin is removed, making the sequence impossible. Furthermore, modern $\text{CO}_2$ extinguishers typically use a squeeze trigger mechanism, not a separate "release lever" that is pulled *up* after the pin is removed and the valve is opened. * **C) open valve and pull pin:** This is incorrect. As in option A, the safety pin must be removed *before* the valve can be fully operated. * **D) pull pin, open valve, and pull up on release lever:** This is incorrect. While the first two steps (pull pin, open valve) are correct, adding "pull up on release lever" describes an action that is not part of the standard $\text{CO}_2$ operation procedure. The action of squeezing the valve *is* the release mechanism. This extra step is redundant and inaccurate for the type of head mechanism typically illustrated.