I. Project Overview

Beijing Chuiyangliu Hospital is a Grade II Class A general hospital located in Chaoyang District, Beijing. In recent years, with the continuous construction of residential communities in the surrounding areas, and as Chuiyangliu Hospital is the largest general hospital in the nearby area, the hospital's outpatient volume has risen rapidly; at the same time, the surgeries involved (such as cardiac surgery, joint replacement, and ophthalmology) have imposed increasingly high aseptic requirements. Under these circumstances, in line with its own development needs, the hospital decided to convert the original operating rooms into a clean operating department complying with national code requirements. The operating rooms are located on the top floor of the general ward building, which has 8 floors in total. Since the original operating rooms had no machine room, the machine room for this clean operating department was arranged on the roof, where a lightweight machine room constructed of color steel sandwich panels was built. The total floor area of the operating department floor is approximately 1000m². According to the hospital's requirements, a comprehensive clean operating department comprising 6 operating rooms and their auxiliary rooms was to be built on this floor. The 6 operating rooms include 2 Class Ⅰ operating rooms, 2 Class Ⅱ operating rooms, and 2 Class Ⅲ operating rooms.

In addition to meeting the client's requirements for the functional use of the clean operating department, the design scheme had to implement, to the letter, the parameters and requirements of the "Standard" and the "Code". The operating rooms should have complete functions, the systems should be advanced, and energy saving in operation should be considered. The new concepts and new measures put forward in the standard and code should be realized as far as possible, so as to maintain a domestically advanced level for a considerable period of time. Since this project is a renovation project, the redesign also had to take into account the actual site conditions, the locations of water supply and drainage, and other factors. Based on the actual site conditions and the hospital's requirements, the design work was completed in September 2001, construction began in October of the same year, and the project was completed in early 2002. In the same year, it passed the comprehensive performance acceptance conducted by the National Building Engineering Quality Supervision and Inspection Center. It has been in use ever since and has been well received by the client.

II. Floor Plan Layout

In the floor plan design, we strove to make as few changes as possible to the original civil structure, the water supply and drainage locations, etc., while satisfying the requirements of the new standard, and at the same time making the "renovation" as good as "new construction".

Features of the operating department layout:

(1) Based on the characteristics of the original building, the clean operating department was arranged in a three-corridor form: the central corridor serves as the clean corridor, used for preoperative patients and clean items; the corridors on both sides serve as cleaning corridors, used for postoperative patients and soiled items.

(2) The particularly clean Class Ⅰ and Class Ⅱ operating rooms were grouped together, and the Class Ⅲ operating rooms sharing a common air system were grouped together, which facilitates both operation and management and the duct and pipe routing design of each system. Meanwhile, to meet the radiation protection requirement, one Class Ⅰ operating room used for orthopedic joint replacement was given a lead-plate envelope structure, and a lead-shielded observation room for medical staff was provided inside this operating room.

(3) The pre-anesthesia room was placed next to the anesthesiologists' office for ease of operation. Separate offices were provided for the head nurse and the chief anesthesiologist.

(4) Both the drug storage room and the disposable items storeroom are provided with transfer facilities equipped with ultraviolet disinfection that span the clean zone and the non-clean zone; that is, the dirty outer packaging of drugs and disposable items is removed in the non-clean zone, and after ultraviolet disinfection in the pass-through window, the items enter the clean zone ready for use.

(5) So that disinfected items can enter the clean zone directly and the possibility of contamination during transport can be reduced, a double-door autoclave was adopted for item disinfection: instruments and dressings are washed and packed in the non-clean zone, disinfected through the double-door autoclave, and the disinfected items can then be taken out directly in the clean zone.

III. Air-Conditioning and Purification System

(1) System division. In accordance with the provisions of the new standard, and taking into account energy saving and convenience of operation and management, the entire clean operating department and the ICU ward are divided into six independent air-conditioning and purification systems (J-1~J-6): Class I operating room (1) and the extracorporeal circulation auxiliary room share one purification air conditioning system (J-1);

Class I operating room (2) has one purification air conditioning system (J-2);

Class II operating rooms (1) and (2) each have a separate purification air conditioning system (J-3 to J-4);

The 2 Class III operating rooms share one purification air conditioning system (J-5);

The other auxiliary rooms of the surgical department share one purification air conditioning system (J-6).

In this way, whichever operating room is in use, its corresponding system is turned on, and the purification systems of the unused operating rooms are not turned on, so as to achieve the purpose of energy saving. However, the auxiliary room systems serving the operating rooms must be turned on regardless of which operating room is in use.

(2) System composition. The operating room systems each consist of a fresh air system, a purification air conditioning system, and an exhaust system within the operating room. The surgical department auxiliary rooms and the ICU ward systems each consist of a fresh air system and a purification air conditioning system. Each system adopts an independent fresh air system; the fresh air units all adopt a new fresh air treatment measure with three-stage filtration of coarse, medium, and sub-high efficiency, but the fresh air units do not undertake the heat and moisture treatment of the air; the heat and moisture treatment is undertaken by the air conditioning units. The exhaust units of each operating room system adopt exhaust air treatment measures with two-stage filtration of sub-high efficiency and medium efficiency. The air purification treatment process is shown in Figure 1.

Fresh air → nylon mesh → coarse-medium efficiency filter → sub-high efficiency filter → (return air ← operating room) → medium efficiency filter → high efficiency filter

Figure 1 Schematic diagram of the air purification treatment process

(3) System cooling source, heating source, and humidification source. The summer cooling source of the air conditioning system is provided by one air-cooled water chiller unit, and the winter heating source uses steam provided by the hospital's original boiler room. Since the hospital's clean surgical department belongs to biological cleanrooms, the growth of bacteria should be avoided as much as possible; therefore, the humidification of each system should not adopt the form of water humidification, but should adopt steam humidification, and the steam is also provided by the hospital's original boiler room.

(4) Selection of system configuration. Since the air change rates of the clean operating rooms are all relatively large, even the Class III operating room, which has the minimum air change rate requirement, must reach 24 air changes per hour according to the national standard. In addition, since personnel are concentrated in the operating room during surgery, the fresh air requirement is large, and the heat loads from personnel, lighting, and equipment are all relatively large. Therefore, in order to achieve the purpose of energy saving, all purification air conditioning systems adopt the secondary return air system. Considering the practical operability of operation, the primary and secondary return air ratios and the fresh air volume are fixed throughout the year. The heat and moisture treatment process of the system is shown in Figure 2. The Class I operating room adopts secondary return air, with the fresh air ratio unchanged throughout the year.

Fresh air $L_w$ → fresh air unit → combined air conditioning unit → supply air $L_s$ → operating room → exhaust air; operating room → return air $Lh$ → $L{h1}$, $L_{h2}$ → combined air conditioning unit; air leakage

Figure 2 Schematic diagram of the system heat and moisture treatment process

IV. Indoor Air Distribution

(1) Air distribution form. The supply air in the clean operating rooms, according to the provisions of the national standard, adopts the form of centralized arrangement above the operating table, while the return air adopts the form of continuously arranged return air outlets at the lower parts on both sides of the operating table. The size of the centralized air supply device meets the dimensional requirements of the national standard; the return air velocity is ≤2m/s; the return air outlets adopt the vertical louver form that is not prone to dust accumulation, and adopt adjustable air outlets with primary-efficiency filtration. Other clean auxiliary rooms adopt an air distribution scheme with supply air uniformly arranged at the top and return air from both lower sides (or a single lower side), while the clean corridor and the cleaning corridor adopt the top-supply, top-return air distribution scheme.

(2) Constant air volume device for clean operating rooms. Since the supply air systems of clean operating rooms are all equipped with HEPA filters, and the initial operating resistance of a HEPA filter differs from its final resistance by about 100%, this brings considerable trouble to operation and management. If the system air volume is adjusted too high at the initial stage of operation, problems such as increased noise and energy waste will arise. If, on the other hand, the initial operating air volume is adjusted to an appropriate level, the system air volume has to be continuously adjusted as the resistance of the HEPA filter increases; moreover, since each operating room is used with a different frequency, it is almost impossible to always satisfy the air volume requirements during actual operation—especially as air volume is a basic parameter for achieving room purification and asepsis. To solve this problem, we adopted the Venturi constant-air-volume ventilation control valve from Phenix Control of the United States. The Venturi valve can automatically compensate for the pressure balance of each air duct according to the actual operating conditions of the system, and always ensure that the air volume passing through it equals the set value, with an error within ±5%. In this way, the above problems are solved, and the balance of supply, return, and exhaust air volumes is always guaranteed, which greatly facilitates the actual operation and management work.

V. Drawings of the Operating Department

The plan view of the clean operating rooms is shown in Figure 3, and the zoning diagram and flow chart of the clean operating department are shown in Figure 4 and Figure 5.

Figure 3　Plan view of the clean operating rooms of Beijing Chuiyangliu Hospital Figure 4 Floor plan of the Clean Operating Department of Beijing Chuiyangliu Hospital

Figure 5 Flow chart of the Clean Operating Department of Beijing Chuiyangliu Hospital Figure 4 Zoning diagram of the clean operating department of Beijing Chuiyangliu Hospital