The person who notices a strange smell briefly becomes more important than the written schedule.

The person who notices something wrong becomes momentarily more important than the plan. A strange smell, an unusual sound, a wrong feeling in a room outranks the schedule, because direct perception of a developing problem is worth more than any amount of prior arrangement. Hierarchy should invert at that moment and often does not.

So say the thing even when it will sound foolish, and even when you are junior. And if you are running something, make it clear in advance that anyone can stop the process for something they cannot yet explain. Most of the value of that permission comes from having granted it before it was needed.