Applies to all fixed extinguishing systems that use dry chemical as the agent and are installed to meet a particular OSHA standard; these systems must also comply with the general requirements of 1910.160. The employer must ensure that dry chemical agents are compatible with any foams or wetting agents they are used with. Dry chemical agents of different compositions may not be mixed, and systems must be refilled with the chemical stated on the approval nameplate or an equivalent compatible material. Where a dry chemical discharge may obscure vision, the employer must provide a pre-discharge employee alarm that complies with 1910.165 and gives employees time to exit the discharge area safely before discharge. The dry chemical supply of all systems other than stored pressure systems must be sampled at least annually to confirm it is free of moisture that could cause caking or lumps. The rate of application must be such that the system's designed concentration is reached within 30 seconds of initial discharge. Non-mandatory Appendix A to Subpart L suggests a simple moisture check: a lump of agent dropped from four inches should crumble into fine particles.
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