如果你曾看到消防员穿戴全面罩防毒面具时，背上还有一个空气瓶，那么你就见过SCBA系统了。
If you have ever seen a firefighter wearing a full-face mask with an air tank on his or her back, then you have seen an SCBA system.
尽管空气中到处漂浮着粉尘和沙土，但他们没有一个人戴有防护面具，其中有一些人还说他们已经几年没洗过澡了。
None wore face masks, despite a pall of silica dust in the air, and some said they had not showered in years.
罐中的风扇使空气流过过滤器，这样净化的空气通过软管达到面具。
The canister USES a fan to force air through the filter, and then the purified air runs through a hose to the mask.
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