The various types of clean rooms in the clean operating department are biological clean rooms, and their primary objective should be the control of viable particles; therefore, the various types of clean rooms should be classified according to the bacterial concentration in the air.

3.2.1 Classification of Clean Operating Rooms

The classification of clean operating rooms is shown in Table 3.4.

Table 3.4 Class Standards for Clean Operating Rooms in China (As-Built or At-Rest)

Class Name of Operating Room Maximum average bacterial concentration by settling (floating) method, operating zone Maximum average bacterial concentration by settling (floating) method, surrounding zone Maximum surface bacterial contamination density Air cleanliness class, operating zone Air cleanliness class, surrounding zone
Ⅰ Special clean operating room 0.2 CFU/30min φ90 dish (5 CFU/m³) 0.4 CFU/30min φ90 dish (10 CFU/m³) 5 CFU/cm² Class 100 Class 1 000
Ⅱ Standard clean operating room 0.75 CFU/30min φ90 dish (25 CFU/m³) 1.5 CFU/30min φ90 dish (50 CFU/m³) 5 CFU/cm² Class 1 000 Class 10 000
Ⅲ General clean operating room 2 CFU/30min φ90 dish (75 CFU/m³) 4 CFU/30min φ90 dish (150 CFU/m³) 5 CFU/cm² Class 10 000 Class 100 000
Ⅳ Quasi-clean operating room 5 CFU/30min φ90 dish (175 CFU/m³) 5 CFU/30min φ90 dish (175 CFU/m³) 5 CFU/cm² Class 300 000 Class 300 000

Note: The explanations and data in ( ) correspond to each other. The bacterial concentration is the directly measured result, not a result of mutual conversion between the settling method and the floating method.

3.2.2 Classification of Clean Auxiliary Rooms

The classification of clean auxiliary rooms is shown in Table 3.5. Table 3.5　Grade standards for clean auxiliary rooms of clean operating departments in China (empty or at-rest state)

Grade Maximum average bacterial concentration by settling method (floating method) Maximum surface bacterial contamination density Air cleanliness class
Ⅰ Local: 0.2 per 30min, φ90 dish (5 per m³) Other areas: 0.4 per 30min, φ90 dish (10 per m³) 5 per cm² Class 1 000 (locally Class 100)
Ⅱ 1.5 per 30min, φ90 dish (50 per m³) 5 per cm² Class 10 000
Ⅲ 4 per 30min, φ90 dish (150 per m³) 5 per cm² Class 100 000
Ⅳ 5 per 30min, φ90 dish (175 per m³) 5 per cm² Class 300 000

Note: The bacterial concentration is the directly measured result, not a result converted between the settling method and the floating method.

[Reference]

① The standards recommended by the World Health Organization are shown in Table 3.6.

Table 3.6　WHO grade standards for various types of hospital rooms

Level Required level cfu/m³ Room types
Ⅰ Minimum bacterial count <10 Organ transplant, cardiovascular and orthopedic operating rooms, protective isolation rooms, etc., laboratories for infusion-type injectable preparation
Ⅱ Low bacterial count <200 Aseptic or other operating rooms (except Class Ⅰ), emergency operating rooms, supply rooms, nurseries, other rooms in the operating area, central sterilization units, postoperative recovery rooms, premature infant rooms, delivery rooms, plaster rooms, intensive care units
Ⅲ General bacterial count 200～500 General wards, washrooms, treatment rooms, cloakrooms, radiology rooms, lounges, corridors, minor operating rooms, bathrooms, massage rooms, physiotherapy rooms, dormitories, storage rooms, dissection rooms, sterile storage rooms, laboratories, kitchens, laundries and related rooms
Ⅳ Air pollution —— Infectious disease departments, isotope rooms
Ⅴ Others —— Toilets, storage rooms, morgues, etc.

This standard also does not clearly distinguish clean operating rooms and does not grade them carefully.

② Hygienic Standard for Disinfection in Hospitals (GB1582-1995) does not give specific standards for operating department rooms (Table 3.7), but only divides various hospital rooms into four grades according to bacterial concentration standards.

Table 3.7　Grade standards for various types of hospital rooms in the disinfection hygiene standard

Environmental category Scope Standard (colony count)
Air/(count/m²) Object surfaces/(count/cm²) Medical staff hands/(count/cm²)
Class Ⅰ Laminar flow clean operating rooms, laminar flow clean wards ≤10 ≤5 ≤5
Class Ⅱ General operating rooms, delivery rooms, nurseries, premature infant rooms, general protective isolation rooms, sterile supply areas, burn wards, intensive care units ≤200 ≤5 ≤5
Class Ⅲ Pediatric wards, obstetrics and gynecology examination rooms, injection rooms, dressing change rooms, treatment rooms, clean areas of supply rooms, emergency rooms, laboratories, various general wards and rooms ≤500 ≤5 ≤5
Class Ⅳ Infectious disease departments and wards / ≤15 ≤15

Because Class Ⅱ in Table 3.7 lists general operating rooms together with delivery rooms, and at the same time the terminology explanation section of this standard does not indicate that general operating rooms are clean operating rooms, the general operating rooms here are not clean operating rooms. Among clean operating rooms, only "laminar flow operating room" without grading clean operating rooms.

It must be emphasized: laminar flow operating rooms must not be confused with clean operating rooms; a laminar flow operating room is merely an advanced form of clean operating room, and it is not entirely equivalent to a clean operating room.

③ The Swiss standard is shown in Table 3.8.

Table 3.8　Grade standards of the Swiss hospital air-conditioning code

Grade Scope Standard (colony count) air/(count/m³)
Ⅰ Highly sterile operating room ≤10
Ⅱ Sterile operating room, contaminated operating room, sterile goods storage room ≤200
Ⅲ Preparation room, post-treatment room, disinfection room, recovery room, other rooms, corridors (sterile goods storage room) ≤500

④ The German standard is shown in Table 3.9.

Table 3.9　Grade standards of the German standard

Grade Scope Standard (filter stages)
Ⅰ Class A operating rooms, Class B operating rooms and other rooms of the surgical department requiring high or very high sterility EU4+EU7+S
Ⅱ Other departments requiring ordinary sterility EU4+EU7

Note: The filtration efficiency of EU4 is 40% by the colorimetric method, that of EU7 is 90% by the colorimetric method, the filtration efficiency of S is 99.97%, and the test dust is 0.3～0.5μm oil droplets.

⑤ The British standard is shown in Table 3.10.

Table 3.10　Grade standards of the British standard

Grade Scope Standard (colony count) at supply air outlet Standard (colony count) within 30cm near the incision during operation Standard (colony count) in 3m×3m operating room
Sterile zone Conventional operating room ≤35 ≤180
Sterile zone Ultraclean operating room ≤0.5 ≤10 (cotton surgical gown) ≤20 (cotton surgical gown)
Sterile zone Scrub room of the operating unit ≤1 (exhaust surgical gown) ≤10 (exhaust surgical gown)
Sterile zone Sterile goods handover area
Sterile zone Sterile goods room
Clean zone Sterile goods storage room — — —
Clean zone Anesthesia equipment room — — —
Clean zone Washroom — — —
Filtered zone Recovery room — — —
Filtered zone Clean corridor — — —
Filtered zone Changing room — — —
Filtered zone Plaster room — — —
Soiled zone Soiled corridor — — —
Soiled zone Soiled utility room — — —

As can be seen from the table, the ultraclean operating room and the conventional operating room, as well as other rooms in the aseptic zone, are similar to Class Ⅰ and Class Ⅱ in China, while the clean zone and the transition zone are similar to Class Ⅲ and Class Ⅳ.

⑥ The Japanese standard is shown in Table 3.11.

Table 3.11　Classification standard of the Japanese standard

Class Scope Standard Standard
Airborne bacteria/(count/m³) Cross-sectional air velocity or air change rate
Ⅰ Highly clean zone: biological clean operating room <10 Vertical unidirectional flow 0.35m/s, horizontal unidirectional flow 0.45m/s
Ⅱ Clean zone: general operating rooms, auxiliary rooms, corridors, etc. <200 20 times/h
Ⅲ Quasi-clean zone: recovery rooms, ICU, etc. <200 10 times/h
Ⅳ Generally clean zone: family waiting rooms, doctors' offices 200～500 8 times/h
Ⅴ Contamination control zone: bathrooms, toilets, waste disposal rooms Total exhaust 12 times/h

⑦ The American standard is shown in Table 3.12.

Table 3.12　Classification standard of the American College of Surgeons standard

Class Scope Standard
Airborne bacteria/(count/m³)
Ⅰ Clean surgery (e.g., artificial organ transplantation) ≤35
Ⅱ Quasi-clean surgery ≤175
Ⅲ General surgery ≤700