Abstract: At 12:30 p.m. on June 1, 2017, Employee #1, employed by a company providing fire sprinkler systems, was engaged in fireproofing work at a seven-story building. He was gathering tools and material to extend a standpipe up one floor. Employee #1 began to unscrew the 6-inch Grinnell Mechanical Grooved Lock-In Cap with a ratchet and pipe wrench. He removed the cap before verifying that the pipe had been depressurized and the compressor disabled. The standpipe was under compressed air pressure, and the cap flew off and struck Employee #1's face. Emergency services were called, and Employee #1 was transported to the hospital. He was admitted and treated for a fractured jaw, a fractured nose, and a tooth that broke off when he was struck.