What is the shelf life of 3M's filtering facepiece respirators?

3M随弃式呼吸防口罩的存放期是多长？

In the event of a fire, wear full protective clothing and NIOSH-approved self-contained breathing apparatus with full facepiece operated in the pressure demand or other positive pressure mode.

果发生火灾，请要求的压力下，衣和国立职业安全与健康研究所批准的呼吸器械和口罩。