Preventing infections is a challenge in any emergency department. In particular, communicable infections like tuberculosis, measles, and influenza can be spread through airborne pathogens, putting patients at risk. 急诊室需要考虑他们的暖通空调控制系统如何通过适当的暖通空调设计来对抗这些感染的传播.
More Air Means Cleaner Air
In the past, HVAC designs included conditioning the air (for temperature and humidity), filtering the air (through two filter banks) and sending it toward dirtier or common areas. These traditional hospital HVAC designs returned 80% of the air with 20% going to exhaust. Over the past 20 years, however, designs have provided far more outside air. Many are being designed with 100% outside air purge systems, meaning no air is returned from a space and reintroduced into the supply air system. Recognizing that a certain percentage of infectious patients walk into the ED and must wait to be triaged, many ED waiting rooms and triage areas as well as isolation rooms should be designed using 100% exhaust, and using 100% outside air should be considered.
And Moving Air Means Cleaner Air
Within individual spaces, the effectiveness of a venting system depends on where the air is introduced into the space. The high/low strategy for vent placement is recommended for isolation, resuscitation, and trauma spaces, where a vertical sterile zone of 24” to 84” above the finished floor is established, i.e., where minimal relative contaminant levels exist. 使用这种结构会大大减少垂直分层的可能性，也会大大减少携带空气传染的未受干扰的停滞空气袋的存在. Thus, there is less chance the HVAC system can be impaired.
Airborne Contaminants Require Different Filtration Methods
For airborne pathogens, there are basically two filtration methods: particulate and ultraviolet germicidal irradiation (UVGI). Because each contaminant is a different size and has a different level of urgency, filtration methods can vary. Nevertheless, if a facility would like to eliminate most pathogens, a combination of high-efficiency particulate air or ultra-low particulate air and UVGI would be the solution.
For large EDs, for example in larger metropolitan areas seeing 100+ patients per day, higher efficiencies may be prudent because the risk for certain contagion is higher. In these cases, 可以使用UVGI过滤器(类似于简单的荧光灯)，因为它可以从0到0对微生物致命.1+ microns, which includes the most penetrating particles such as yellow fever, Ebola, hepatitis A, and influenza.
UVGI已被证明是控制和摧毁卫生保健领域细菌和真菌病原体的最有效手段. Their best performance has been recorded in static installations where UVGI is focused on stationary surfaces. And, while UVGI is being used more and more to target contagions on coils and filters, UVGI是否能在更大范围内或在暖通空调系统典型速度的流动气流中有效，证据尚不充分.
Clean the Exhaust Air Too
仅仅明智地将排气管放置在远离主干道或大量人群可能聚集的地方是不够的. Exhaust air should be cleaned for the same reason intake air needs to be filtered. Wind patterns are unpredictable, 使有害污染物有可能回流到为维修人员或其他ED工作人员服务的公共区域或空间. 安装在屋顶上的装有HEPA最终过滤器的风扇可以直接向上排放15-20英尺的空气，以防止再污染.
Pressurization Monitors: Consider for Individual Rooms
因为患者治疗室比走廊或工作人员工作区有更高的空气传播传染病的风险, 可能值得考虑像在隔离室或急诊室的个人病房负压室中发现的系统那样进行气流和压力监测. 单个房间内的压力将相对于相邻走廊进行测量，并设置为略负. This can help limit the spread of contagions from the source room.
Because of recent technological advances, these devices have excellent sensitivity and reliability and are becoming less expensive. 标准设备可以从建筑或能源管理控制供应商那里购买，远程监控，以及由于开放协议控制语言而集成到患者分配系统中.
Don’t Forget Staff Training
Whatever HVAC design elements are incorporated in hospital EDs to prepare them for airborne contaminants, it is also critical for staff to have a basic knowledge of the HVAC system, specifically air flow and pressurization schemes. 只有全面了解系统配置与气流区域和分区的关系，工作人员才能在事件发生时快速隔离某些区域.
Beyond the structure of the system, staff must know how to deal with specific contaminants. For instance, the staff needs to evacuate when a hazardous contagion is detected indoors, whereas sheltering in-place is the appropriate response when one is detected outdoors.
Finally, 通过调试或验收测试过程验证程序或HVAC系统功能是至关重要的. HVAC and operations staff must be familiar with the steps the system goes through when initiated. Remember that no design measures can replace a crisis-prepared staff.
