What does the manual release tool do when the PSU fails?

The manual release tool serves a crucial function during a failure of the Passenger Service Unit (PSU). When the PSU fails, its primary purpose is to allow crew members or authorized personnel to manually open the PSU. This is essential because a failed PSU may prevent passengers from accessing necessary items such as oxygen masks or lights, which are vital for safety during emergencies. By manually opening the PSU using the release tool, crew members can ensure that passengers are able to receive the assistance they need until the issue is resolved.

The other options, while they might touch on important safety procedures, do not accurately describe the specific action that the manual release tool is designed to perform in this context. The focus of the manual release tool is to provide a means to access the PSU directly.