During a vacuum test, the vacuum inside a pump should not drop in excess of how many inches in 5 minutes?

The situation described pertains to maintaining an optimal vacuum level in a pump during testing. The standard threshold for acceptable drop in vacuum over a specified period is set to ensure the integrity and efficiency of a pump's operation. Particularly, a vacuum drop of no more than 10 inches in 5 minutes is a widely recognized guideline. This standard helps ensure that the pump is functioning properly and that there are no significant leaks or operational inefficiencies present. Exceeding this threshold could indicate issues such as deterioration of pump seals, leaks in the vacuum system, or other mechanical failures that need to be addressed to ensure safety and functionality in a firefighting or emergency response scenario.

Therefore, the correct answer, which reflects the maximum allowable drop, is established at 10 inches, as this provides a reliable parameter for assessing pump performance during a vacuum test.