Good news! If you've been issued (or know someone who's been issued) the Navy's new flame resistant variant coveralls, and were doubtful of their fire resistance, you can rest easy!
Hull Maintenance Technician 3rd Class Ryan Davis inadvertently tested the coveralls' claims aboard the USS George H.W. Bush while grinding a chair foundation, according to this NavyTimes article. After a piece of hot metal landed on his coveralls, the fire watch (Sonar Technician 1st Class Thomas Pauli) noticed a small flame and was able to quickly pat it out with just his hand.
Davis said he wasn't sure how long the hot slag was on his uniform, and he didn't notice the small flame until the fire watch was able to extinguish it. This is a great success for the new FRV coveralls - demonstrating that the flame-resistant coating will indeed prevent a fire from spreading and the coveralls from melting. Last year's utility coveralls, made of a 50/50 cotton and synthetic blend, will quickly catch on fire until completely engulfed and melt.
There have been some complaints from sailors about the new coveralls, though. They are heavier and the fitment is not as good as last year's utility coveralls, but after this impromptu but effective test, there is at least one more sailor grateful for this improved uniform.