Interfering in a Dangerous Situation
You're interpreting in an auto mechanics class, and the teacher is explaining about torches and the appropriate mixtures. Your husband owns an auto shop, so you're somewhat familiar with the subject. The Deaf student is putting his mixture into the torch. You're pretty sure he didn't follow the instructions and that if he lights the torch he could blow the place up. Without waiting for the instructor to come over and check his work, he's getting ready to light his torch.
An Interpreter's Perspective:
Common sense tells you to value the lives of others over any professional code. In a situation like this, yes, I will probably say or do something.
A Deaf Consumer's Perspective:
If you value your life, then you should definitely tell the student to check with the instructor before lighting the mixture.