What has to happen before a laser cutter is used again after a fire?

This answer covers an enclosed, interlocked machine that is Class 1 or Class 2 in the configuration you run. An open-frame, open-bed, pass-through or converted machine, or one that is Class 3B or 4 in normal use, is not covered here. It needs a laser safety officer and a written program first, and if no one can be designated, the answer is not yet. A school without a designated person to release the machine is in the same not-yet position.

The building comes first. After a larger fire, nobody goes back into the building until it is cleared; Carnegie Mellon’s procedure says to remain outside until cleared for re-entry. Then report it. The University of Washington’s research-laser manual requires notifying EH&S immediately, after emergency care, when an incident involves a laser or fire, and its cutter sheet says to report all fires, injuries and near misses.

Three university research-laser programs hold the laser until someone with authority approves it, and only Ohio State’s rule names fire; UT Austin’s and UC Berkeley’s are written for laser injuries and exposures. Ohio State says that after any laser incident involving injury or fire, operations may not continue until its laser safety officer approves. UT Austin keeps a laser system out of service until the investigation and corrective actions are done, and its laser safety officer and committee review the corrective actions before operations resume. UC Berkeley requires its officer and committee to review the incident, approve corrective actions and approve a restart. These are research-laser programs with a laser safety officer, so treat them as examples of the steps, not as rules your school must copy.

In a school, that translates to: take the machine out of service now (power down, secure it, label it); report it the same day to the person your procedure names; write down what was being cut, what happened and what was found; let only authorized service work on or open the machine; and record what changed before it is released in writing.