In a clean surgical department, various types of clean rooms are graded according to bacterial concentration, with air cleanliness class serving as the necessary guarantee condition, and the bacterial concentration in each zone of the operating room is further regulated by zone and by grade with a specified maximum allowable bacterial count. These discussions are detailed in Chapter 3, "Composition and Grades of the Clean Surgical Department." What this chapter is to elaborate is that the technical standards for the various types of clean rooms in the clean surgical department should all be based on the premise that, after the purification air-conditioning system (or equipment) has been operating and reached the specified self-purification time, the average concentrations of airborne bacteria or settling bacteria and the air cleanliness class (including both particle sizes of $geqslant 0.5mu m$ and $5mu m$) achieved under empty or static conditions all comply with the requirements listed in Chapter 3. After meeting the requirements of the corresponding grade, the other relevant technical indicators should also comply with the specified values or ranges in Table 4.1 of the Code. The 9 indicators included in Table 4.1 appear to be mutually independent, but in fact several of the main indicators are interrelated and mutually influential; for example, the static pressure value indicator is also an important indicator for preventing cross-infection, meeting the requirement of maintaining the air quality of the internal environment of the surgical department, and ensuring the prevention of interference with the surgical department from other departments through the air.

The relationships of mutual influence among these technical indicators, as shown in Figures 4.1 and 4.2, can directly affect surgical quality and even affect incision infection:

Figure 4.1　Influence of Parameters

Figure 4.2　Mutual Influence of Parameter Changes

Cleanliness (and bacterial concentration): mainly affects the contamination of incisions and the bacterial concentration in the air.

Temperature and humidity: affect the bacterial shedding of medical staff and patients as well as the survival and reproduction conditions of bacteria, and also affect the comfort of medical staff and the surgical outcome.

Static pressure difference: affects the mutual air leakage between operating rooms, causing cross-infection. Other parameters will also directly or indirectly affect the use of the operating room, or involve associated hazards of mutual cross-infection.

These mutual influences refer to the effects that may arise during the operation of the operating room when parameters change significantly. For example, when the filter is severely clogged, the fresh air volume will be greatly reduced or the air change rate will decrease considerably; although the fresh air ratio changes little, this phenomenon can occur. When the fresh air volume decreases, the static pressure will also decrease accordingly; when the supply air volume of the unidirectional flow decreases, the cross-sectional air velocity drops considerably, which will directly affect the airflow organization characteristics of the unidirectional flow.

Table 4.1 Main Technical Indicators

Name Minimum static pressure/Pa degree Minimum static pressure/Pa to adjacent lower-grade cleanroom Air change rate/(times/h) Average cross-sectional air velocity at working surface height of operating table in operating zone (or local Class 100 work zone)/(m/s) Self-cleaning time/min Temperature/℃ Relative humidity/% Minimum fresh air volume m³/(h·h) Minimum fresh air volume times/h Noise/dB(A) Minimum illuminance/lx
Special clean operating room ++ +8 — 0.25~0.30 ≤15 22~25 40~60 60 6 ≤52 ≥350
Standard clean operating room ++ +8 30~36 — ≤25 22~25 40~60 60 6 ≤50 ≥350
General clean operating room + +5 18~22 — ≤30 22~25 35~60 60 4 ≤50 ≥350
Quasi-clean operating room + +5 12~15 — ≤40 22~25 35~60 60 4 ≤50 ≥350
Dedicated preparation room for extracorporeal circulation perfusion + +5 17~20 — — 21~27 ≤60 — 3 ≤60 ≥150
Room for sterile dressings, instruments and disposable items, and precision instrument storage room + +5 10~13 — — 21~27 ≤60 — 3 ≤60 ≥150
Nurses' station + +5 10~13 — — 21~27 ≤60 60 3 ≤60 ≥150
Preparation room (disinfection treatment) + +5 10~13 — — 21~27 ≤60 30 3 ≤60 ≥200
Pre-anesthesia room -- -8 10~13 — — 22~25 30~60 60 4 ≤55 ≥150
Scrub room 0~+ >0 10~13 — — 21~27 ≤65 — 3 ≤55 ≥150
Clean corridor 0~+ 0~+5 10~13 — — 21~27 ≤65 — 3 ≤52 ≥150
Changing room 0~+ 0~+5 8~10 — — 21~27 30~60 — 3 ≤60 ≥200
Recovery room 0 0 8~10 — — 22~25 30~60 — 4 ≤50 ≥200
Cleaning corridor 0~+ 0~+5 8~10 — — 21~27 ≤65 — 3 ≤55 ≥150

Note: 0~+5 means that any number within this range except 0 is acceptable. The minimum fresh air volume shall also comply with the provisions of 4.8-(d) of the Code. In the Code, the obstetric operating room refers to the natural delivery room, which uses full fresh air.