If I'd know I was cming to a place that had nothing but freshair, I would have brought a surgical mask.
如果早知道我要到一个只有新鲜空气的地方来的话，我就会带一只口罩来了。
2
If I'd known I was coming to a place that had nothing but freshair, I would have brought a surgical mask.
如果早知道我来的地方只有新鲜空气，我就会带一只口罩来了。
3
If spraying application is carried out in a limited place like narrow booth, the operator must wear a ventilated mask with an air compressor for feeding filtrated fresh air.