The recrystallizing of the crude trinitrotoluol with easily inflammable solvents such as alcohol, benzol or toluol shall take place in a building standing alone. All solution tubs, crystallizing vessels, centrifuges and conveying apparatus shall be closed in such manner that vapors in dangerous quantities do not escape into the workroom. Proper ventilation of the workroom shall be provided. All platforms in this building shall have an exit into the open air.
34 Pa. Code § 13.195