There must be a high efficiency air filter provided at the air outlet point. 在空气出口点必须提供一台高效空气过滤器。
The Centers for Disease Control says HEPA filters are effective in clearing the air of many particles that cause disease. 疾病控制中心认为高效微粒空气过滤器能有效的清理掉空气中很多可致病的微粒。