What is the first step when responding to a hazardous spill in the laboratory?

The first step when responding to a hazardous spill in the laboratory is to stop the source of the spill. This action is crucial as it prevents further contamination and minimizes the risk to personnel and the environment. By addressing the source, you limit the extent of the exposure and the potential damage that could occur from the hazardous materials involved. This immediate action serves to contain the situation, allowing for a more controlled response subsequently.

After stopping the source of the spill, further procedures can be followed, such as notifying a supervisor or utilizing personal protective equipment, but establishing control over the spill situation is paramount to ensuring safety and managing the incident effectively.