29 CFR § 1910.161 - Fixed extinguishing systems, dry chemical.
(a)Scope and application.This section applies to all fixed extinguishing systems, using dry chemical as the extinguishing agent, installed to meet a particular OSHA standard. These systems shall also comply with § 1910.160.
(2) The employer may not mix together dry chemical extinguishing agents of different compositions. The employer shall assure that dry chemical systems are refilled with the chemical stated on the approval nameplate or an equivalent compatible material.
(3) When dry chemical discharge may obscure vision, the employer shall provide a pre-discharge employee alarm which complies with § 1910.165 and which will give employees time to safely exit from the discharge area prior to system discharge.
(4) The employer shall sample the dry chemical supply of all but stored pressure systems at least annually to assure that the dry chemical supply is free of moisture which may cause the supply to cake or form lumps.