Final answer:
Smoke, toxic vapors, explosion, and tornado are hazards that can be valid reasons for evacuating a workplace, with the exception of tornadoes.
Step-by-step explanation:
The hazards listed in the options A, B, C, and D can all be considered valid reasons for evacuating a workplace. Smoke, toxic vapors, explosion, and tornado can all pose significant risks to the safety and health of employees in a workplace.
However, it is important to note that the question asks for an exception.
Therefore, the correct answer would be D) Tornado, since tornadoes are not typically a hazard that would require immediate evacuation of a workplace.