One rule of working safely is this: don't assume. Make sure you know. See if you can identify the steps required to verify the facts rather than trust the following assumptions:
Your insulating gloves don't have holes.
The switchgear you've tagged out is actually isolated.
Your test leads are safe to use.
Your DMM is set correctly for the measurement you're taking.
You can safely enter the vessel that your coworkers just exited.
You can safely stay in the vessel based on data taken when you entered.
The person you've asked to be your attendant is qualified, has the correct PPE, has reliable communication with first responders, and is capable of safely performing an extraction.
The new batch of the epoxy you've been using has the same ventilation and PPE requirements as the previous batch. Are you sure this one isn't a new formulation that perhaps dries faster but also is more toxic?
