Which action would NOT breach the vacuum system?

Testing a system component with a leak detecting solution is an appropriate procedure in maintaining the integrity of a vacuum system. This action is aimed at identifying any potential leaks that could compromise the system's performance. Typically, a leak detecting solution is a non-invasive method that can help ensure that the system remains sealed and functional without causing any damage or unintended breaches.

In contrast, the other actions could introduce risks to the vacuum system. Cleaning with alcohol may leave residues or introduce contaminants that could affect the system's operation. Opening a valve can create an opening in the system, allowing air and other contaminants to enter, which breaches the vacuum integrity. Similarly, connecting additional components can introduce new pathways for leaks or improper connections that could disrupt the vacuum conditions. Therefore, using a leak detecting solution stands out as a safe practice that supports maintaining the vacuum system’s integrity.