虽然几个团队迅速在会议中心和公共集会的场所建立了与COVID相关的野外医院，并考虑到冠状病毒涌现的替代地点的低音果实，但他人在幕后进行较长的交货时间翻新和转换工作。用于医院，酒店和宿舍。其中许多旨在增加冠状病毒患者重症监护病房和空中感染隔离室的供应，目的是保护医疗保健人员免于生病。

For the retrofits and conversions, health care architects and engineers are seeking the best ways to quickly design code-compliant and safe ICU and airborne infection isolation rooms, suites or wards, in a time of changing intelligence about virus transmission. The main reason for AII, rather than ICU-only rooms, is to keep health care personnel from contracting COVID-19.

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“There is a subtle shift going on about how much transmission is occurring via droplets versus aerosols and in a health care setting, the concern about aerosols is higher because of the interventions, for example intubations, health care workers need to do to help the sick,” says engineer Duncan Phillips, a principal with RWDI, which designs AII rooms by, in part, modeling air flow through computational fluid dynamics (CFD).

Convention center pop-up hospitals, even those with some AII rooms, have been taking two weeks to a month to design, build and occupy. Even on the fast track, the more-complex ICUs or wards with all AII spaces could take one to six months, depending on variables. These include the project size and scope; the level of COVID-19 care; lead times for equipment; the original occupancy of the space; the need to convert the occupancy, which typically means upgrading fire alarm and life-safety systems; the permitting process; the locale; and more, say designers.

Collaboration Is Critical

For speed, many design firms are teaming up with contractors, in contractor-led design-build teams. Collaboration with owners, contractors, suppliers and users is critical to deliver the projects quickly. “Everyone is on the front lines, doing their parts,” says engineer Nolan Rome, U.S. health care director for WSP.

Help for fast-tracking the design of COVID-19 temporary treatment spaces is available from the American Society of Health Care Engineering, ASHRAE’s COVID-19 guidance document and from the American Institute of Architects.

For spaces other than convention centers and public assembly areas, there is more of a push toward ICUs than AII beds, says Timothy E. Krawetz, a health care senior principal for consulting engineer Syska Hennessy Group (SHG). Yet in the COVID-19 era, ICUs are starting to mimic AII rooms, though negative air pressure is not required by code for ICUs, he says.

A negative air pressure system directs air flow in a room through ventilation that generates pressure lower than the room’s surrounding air. Air naturally flows from areas of higher pressure to areas of lower pressure. In AII rooms, the air stays in the room, thanks to the negative pressure, and is exhausted mechanically.

There is no great mystery about the design of AII rooms or ICUs with AII. The pandemic has put pressure on the health care design and construction community to get the rooms designed, approved, built and operating quickly. The goal is to keep the designs simple so they can be deployed and maintained efficiently, with a minimum number of maintenance personnel, says Rome.

WSP正在南卡罗来纳州设计一家临时医院。他说：“我们正在思考像设施运营商，而不是设计工程师。”

One obstacle is equipment lead time, which can vary from three to six months. There is a three- to five-week lead time for ventilators and a four- to six-month lead time for negative-pressure machines, says Kimberly R. Cowman, national director of engineering for Leo A Daly.

There is 30-day delivery for hospital-grade air-handling units, says SHG’s Krawetz.

宋惠乔为期一个月的中旬ICU f投影rom start to finish—that involves gutting two residential floors, formerly for nurses, of a 17-story public hospital building in New York City. The client, partway through design, asked for the capability to switch the rooms to negative pressure. Part of the challenge is that the programs keep changing, mid-design, says Krawetz.

It took SHG 15 days, working 15 to 18 hours every day of the week, to produce the 66 drawings needed for the project. That design work would normally take six months, Krawetz says.

施工正在全天候进行。Krawetz说，预计将在4月15日左右。

For AII spaces, the goal is to manage all contaminants, in the form of gases or droplets, through air flow. Though larger droplets fall, potentially contaminating surfaces, smaller droplets will float and can be inhaled.

混合通风系统

RWDI的Phillips说，最常见的AII空气处理策略是混合通风系统或混合空气分布系统。混合通常会将空气传递到房间的上层，并利用传入的空气在房间周围分布式的动量 - 将清洁的传入空气和房间中的污染物混合在一起。排气管通常在天花板上或患者床后面，将混合空气提取并通过HEPA滤波器净化器移动，然后将其释放到户外或走进走廊上。该过滤器不会捕获COVID-19病毒，但会捕获捕获病毒的颗粒。

Phillips is against mixing ventilation because fresh air is contaminated and pollutants are stirred around the room. Instead, he advocates a displacement ventilation system, which minimizes mixing. DV delivers cooler air into the room low to the floor, through a perforated tube along the floor called a duct sock or through several vents along the floor.

DV之所以起作用，是因为凉爽的通风空气被乘员和设备加热，随着污染物的升高而升起。新鲜空气与受污染的空气没有太多混合。由于新鲜空气升高的速度低，较大的液滴仍将落在地板和其他表面上。

因为小雾滴是光和track with air, they become stratified at the ceiling while the exhaust is pulling them from the room. This turns the upper layer of the room into a storage zone for the fine droplets above the occupied space, says Phillips.

Also, the exhaust at the ceiling level is able to extract the contaminants at a higher concentration because they were not diluted by the mixing, making that exhaust more effective.

Phillips says that the mixing approaches offered in guidance documents don’t describe how to deliver air into the room. Instead, they focus on how to extract air from the space.

“You cannot properly control airborne transmission just by choosing how to exhaust from the room,” he says.

菲利普斯坚持认为，排气必须在正确的位置，但供应量也很重要。“花太多时间担心提取就像试图吸取蜡烛。一旦烧掉嘴唇，您才能成功。”他说。

机械工程师塔里克·阿姆拉尼（Tariq Amlani），建筑物校长Stantec,agrees with the general concept that DV can reduce the overall contaminate concentration in the room. But he cautions that though the directional air flow aspect of DV can help control the flow of contaminates within the space, the strategy is “highly reliant” on the location of the low-level supply grills and high-level exhaust grills.

烧烤位置

Using DV alone “may not help and can actually hurt infection control, if you don’t get the grill locations correct,” Amlani says. “DV or not, in consideration of the current COVID-19 situation, I don’t believe that there would be any differences in the personal protective equipment requirements for the health care workers in these spaces,” he adds.

Amlani is also concerned about keeping the duct sock sanitized. In addition, with DV there are limitations on how cold the supply the air can be without running into comfort issues.

A typical overhead ventilation system can have supply air as cool as 55° F without comfort complaints. With DV, you have a lower limit on your supply air temperature of approximately 65° F, as per the ASHRAE code, says Amlani.

There can be other concerns, he adds. DV relies on cool air “pooling” at the floor level and then “pluming” up as the cool air warms up at heat sources. “If you have a room with a window that can receive direct sunlight, this can be a significant problem,” adds Amlani.

Also, “if you have a room on the perimeter of the building and you are using DV, you will need a secondary decoupled heating system, such as radiant panels or radiant floors to offset envelope heat losses,” says Amlani. “This may not be practical to implement in all buildings and projects.”

其他人则同意DV具有潜力，但只有在正确执行的情况下才有潜力。TLC Engineering首席执行官Michael P. Sheerin说：“存在着独特的挑战。”一个是，低壁扩散器需要在占用病房中有价值区域的追逐中路由。他补充说，由于调整了空气温度，因此它与内部空间的加热，通风和空调支撑不同。

Sheerin concedes that the basic principles of DV—supply air diffusers at the entry and health care worker side of the patient bed and exhaust near the head of the bed—are “time-honored and a sensible means of encouraging a clean-to-less-clean airflow pattern in a space, especially important in an isolation space.”

戴利（Daly）的考曼（Cowman）同意，尽管RWDI“为流离失所通风提供了理由，但这种类型的系统在实践中存在固有的设计挑战。”

The location of the supply diffusers and the ability to keep the area in front of the diffusers clear of equipment would mandate an additional level of coordination with the architecture, equipment planning and hospital operators to ensure the design would perform as intended, says Cowman.

她建议将来研究空气流的最佳设计和分布，以服务于患者隔离室以保护医疗保健工作者。她说：“在所有情况下，供应和排气位置的周到位置都有价值，可以将空气从空间中的空气转移到空间中的肮脏环境。”