I work for a Municipal Electric Utility and here's an example of a fire resistant shirt (5 - 6 cal/sq. cm) worn by one of our linemen who was burned in a secondary fault while hooking up some 120/208V leads to a padmounted transformer. Thank the Good Lord and his PPE, he came out of it with just some 2nd degree burns on his arm.

Don't forget your safety glasses either ... his were burnt and had tiny metal beads melted into the plastic lens of his safety glasses!

(I tried to attach the picture but the file was too large for this site - about a Meg. There's a 97k limit here. Anyway, the right sleeve is charred and just fell off the shirt.)

Needless to say, everyone now has about double the cal/sq. cm. fire rated shirts.