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

3M随弃式呼吸防护口罩存放期是多长时间？

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.

如果发，请要力下，穿保护衣和国立职业安全与健康研究所批准呼吸器械和口罩。