Final answer:
The safest place to be standing when opening a gas regulator is to the side of the regulator to reduce the risk of injury from equipment failure or rapid gas movement.
Step-by-step explanation:
The safest place to be standing when opening a gas regulator is always to the side of the regulator, not in front of it. This position minimizes the risk of injury in case the regulator fails and the gas is released under high pressure. When working in a laboratory setting, safety is paramount. For example, when a second flask containing a vacuum is connected to a flask with gas, and the valve is opened, the gas spontaneously becomes evenly distributed between the flasks. This illustrates how quickly and powerfully gases can move, and by standing to the side, you protect yourself from potential harm from the rapid gas movement or equipment malfunction.