NaAlH4 powder mixed with hexane was placed in two metal trays and dried by placement in a glove box antechamber under vacuum. After several days, the trays were moved into the glove box main chamber. As the powder in one of the trays was being transferred to a container involving scraping of a metal sieve and metal milling balls with a metal spatula, a portion of the powder in the tray spontaneously reacted rapidly, creating a pressure pulse which cracked the window at the back of the glove box. No injuries occurred, and the glove box window was resealed using tape within one to two minutes.