In the event of a train derailment releasing toxic gas, what action should personnel at the School of Dentistry take?

In the situation of a train derailment that results in the release of toxic gas, the most appropriate response for personnel at the School of Dentistry involves a combination of staying inside the building to avoid exposure to the external toxic environment and taking precautions to minimize the intake of contaminated air.

Staying indoors until an "All Clear" signal is provided is a widely recommended practice during hazardous material incidents. This action protects personnel from direct exposure to the toxic gas, which can be difficult to assess in an outdoor environment. Remaining inside allows time for emergency responders to manage the situation and for the toxins to dissipate, if safe to do so.

Additionally, avoiding the use of elevators is crucial in this context. Elevators can serve as conduits for air, and using them might increase the risk of inhalation of toxic gas. Fire safety protocols often encourage using stairs as a means of escape in emergencies, but in this scenario, personnel are advised against using elevators to ensure that they do not inadvertently facilitate additional air intake of harmful substances.

Hence, the combination of both staying indoors until an official clearance is provided and taking steps to limit air intake by avoiding elevators constitutes the safest and most effective response strategy during an incident involving the release of toxic gas.