You are just finishing up some work in a branch circuit panel when a strong chemical smell hits. What should you do? A strong smell means there's some kind of leak or spill. Any time there's a leak or a spill, leave the area immediately.
The logic of airline safety announcements applies here. Help yourself first so that you can help others. That means leave. On your way out, warn others that there's a spill and they need to leave the area — but don't stop walking while you're talking.
After you reach safety, report the problem to the first supervisor you can find. Then report to your own supervisor.