What must be done before any experiment?
A risk assessment must take place.
What are the risks associated with the experiment? What can go wrong? What has gone wrong in the past? If it does go wrong, what is the appropriate action? Where is the fire alarm? Where is the exit.
Most of the time, these questions are speedily answered. Especially in modern laboratories, which are very risk averse these days, there are set procedures and protocols to follow. One of the most basic is never work alone. What are the risks of working alone?