It was previously mentioned that N95 masks can be used in presence or absence of aerosols, or can they only be used in the case of aerosol sprays? / 之前提到过在有无产生气溶胶的情况下可以使用N95口 罩，有无的情况都可以，还是只是在有产生气溶胶的情 况下我们可以使用N95，没有产生的情况只用三层？