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Operating room purification air conditioning system design

| 2006-09-28

Text / Jin Chun


[Abstract] The main task of the operating room purification air conditioning system is to provide the operating room with high quality and clean air environment. To achieve the above purpose, the air conditioning system must have the following functions: 1. To dilute and remove the chemical pollutants in the operating room, including Anesthetic gases, other explosive and toxic gases; 2. Control of bacterial contamination in the operating room, including the operating room itself and invasive alien bacteria and filtration viruses; 3. Control of the operating room temperature and humidity environment, suitable for surgery on the environment , And provide a comfortable environment for patients and medical staff.


      [Key words] air conditioning system control bacterial contamination temperature and humidity


introduction


Control of bacterial and cross-infection in the operating room of the hospital has always been the focus of the hospital's work. It is also the primary task of the operating room air-conditioning system. There are many ways of causing infection, such as infection caused by the air-conditioning unit itself or system design and installation, Of course, there are operational management issues, in order to make the design more comprehensive and more appropriate solution to these problems, operating room air conditioning system to be different from the general air conditioning, should have the following characteristics:


  High-tech air volume


Chemical contaminants can not be removed by filtration. It can only be diluted and discharged through a large amount of fresh air. Therefore, the operating room air conditioning system must have a high and stable fresh air volume.


    In some countries the standard allows for a lower fresh air volume, but must be accompanied by a higher number of air cycles at which ASHRAE makes it clear that 100% of the fresh air system is only required in countries with local regulations. Therefore, with air circulation from the same operating room, the following fresh air volume is permissible:


(1) Particularly clean operating room (I level) fresh air volume not less than 1000m3 / h.


(2) The standard clean operating room (Class II) fresh air volume of not less than 800 m3 / h.


(3) General clean room (Class III) fresh air volume of not less than 800 m3 / h.


(4) clean room (Class IV) fresh air volume not less than 25% of the air supply.


  Air supply should be through the ceiling air supply, return air should be through the sides at a distance of 150mm above the ground, 500mm below the location of the return air, the outlet must be one-way with high efficiency filter, the general supply air flow The device does not apply to the operating room.


  Airflow pattern and pressure distribution


Colony as a particle moves in the direction and speed of the air, so controlling the form of air flow is of great importance. Air flow control should be at two levels: one is overall and one is local. The overall control is to control the movement within the operating room between the operating room and its adjacent room. One of the most important principles is that air flow should flow from the cleanest room to the next clean room. Therefore, the air flow must flow from the operating room to the clean walkway to ensure that the pollutants will not invade. According to the actual experience , Class I clean operating room should maintain a positive pressure of 25Pa, Class II clean operating room should maintain a positive pressure of 20Pa, Class III clean operating room should maintain a positive pressure of 15Pa, Class IV clean operating room should maintain a positive pressure of 10Pa, clean walkway should be maintained 5 ~ 10Pa positive pressure, when the operating room needs negative pressure should be designed separately, it is recommended to install differential pressure sensor to control the operating room pressure, the operating room floor, wall, ceiling doors must be absolutely sealed, special operating room can also press Positive and negative pressure conversion design, in the event of medical malpractice, the operating room can be immediately changed from positive pressure to negative pressure, to avoid pollution of the outdoor environment.


Taking into account the characteristics of the clean operation of the security system and China's national conditions, for the purification of air-conditioning systems, our hospital "clean surgical department construction standards" stressed:


(1) Class I and II clean operating rooms adopt independently set air purifying and air-conditioning units. Class III and IV clean operating rooms allow 2 to 3 systems to be used together.


(2) The operating room in the clean operating room and auxiliary room separate from the air-conditioning system.


(3) An independent fresh air system should be installed.


(4) The entire surgical department should always be in a controlled state and can not affect the orderly gradient pressure distribution of the entire surgical department due to the stoppage of an operating room. Otherwise, the directional flow of the positive pressure air flow between the chambers will be destroyed and the cross Infected or contaminated indoor environment.


  3. Temperature and humidity control


The Technical Specifications for the Construction of Clean Operation Department of the Hospital stipulates that the operating room temperature should be controlled at 22-25 ℃ and humidity 40-60% RH according to different surgical requirements. The temperature of clean walkway and auxiliary room should be controlled at 21-27 ℃ , Humidity in the range of 30 ~ 60% RH.


  4. Air conditioning unit requirements


The principle of operating room air conditioners is no different from that of general air conditioners. However, due to its rigorous requirements on air environment, special measures should be taken to improve the sealing and reliability and should be easy to clean and disinfect. The following requirements should be met:


(1) The inner layer of the unit is made of spray-cold-rolled steel plate or stainless steel plate which is not bactericidal, the outer layer is made of spray-coated steel plate or color steel plate, the inner and outer layers are filled with polyurethane foaming material, So as to ensure the adiabatic performance of the unit and the air leakage rate and eliminate the appearance of dew condensation in the cold bridge and the operation shell, and the arc transition process should be adopted in the inner layer to reduce the possibility of bacteriosis and facilitate the cleaning.


(2) Fresh air filter efficiency and efficiency filters should be used hydrophobic bulk dust, high-performance filters.


(3) unit electric heater made of stainless steel light pipe, smooth surface, corrosion resistance, easy to dust, easy to clean.


(4) Under the pressure of the table cold coil should ensure that the condensation of water discharge, no water, no water seal.


(5) Medium-efficiency filter is set in the positive pressure section, should ensure that the evaporation coil is free from dust pollution, to completely avoid moisture in the filter.


(6) Table cold coil should be used disinfection and sterilization measures, surface wind speed is not more than 2m / s, should be made of hydrophilic film aluminum foil flat fins, will not produce water spores bacteria and water phenomenon.


(7) Unit sealing is good, the air leakage rate should not exceed 0.5%.


(8) All air filters should be equipped with differential pressure alarm device before and after, should be promptly remind the user to replace the filter, such as the use of regular replacement, the control system should regularly remind the user to replace the filter.


(9) indoor humidity priority control program should be used, the humidity control range of 45 to 70%, to ensure clean room temperature and humidity control and high efficiency filter duct before the relative humidity of not more than 75%, to prevent the humid air lead to secondary pollution.


(10) The water tray with stainless steel fillet, large drainage slope, no transverse seams, eliminate stagnant water.


(11) The use of dry steam humidifier or electrode humidifier, humidifier to ensure that no water after the shutdown.


(12) fans should be imported low noise centrifugal dumping, transmission for the belt drive.


(13) When the unit is shut down, the fresh air shut-off valve closes at the same time. If the blower needs to be shut down in delay, the delay time should be set by the user.


(14) Unit should be equipped with UV lamp sterilization.


(15) The unit shall be equipped with manual forced power-on function to ensure that the unit can still be started when the control system fails.


(16) The unit should be able to match the inverter control fan operation to meet the operating room air conditioning system requirements.


(17) The unit should be used to achieve a variety of conditions mode of operation, precise control of indoor temperature and humidity can be carried out through the central monitoring of communications or networking with BMS building automation system.


  Conclusion


Hospital clean surgical department air-conditioning system design, centralized treatment of fresh air should give priority to, and the use of fixed air volume, high-wind air volume design, the entire clean surgical department is always under positive pressure control and to ensure that the pressure gradient distribution, air-conditioned box fan using frequency Fan, to ensure the insulation performance of the unit and air leakage rate, to prevent cold bridge and operating shell condensation phenomenon, reduce the likelihood of sterilization, easy to clean.


references


    1. Xu Zhonglin "Air Clean Technology Principle" Tongji University Press 1998


    2. Chinese Health Economics Society of Health Building Professional Committee


"2002 Beijing Hospital Architecture Design and Equipment International Symposium Proceedings"


    3. "Clean and Air Conditioning Technology" 2002 fourth issue


  Technical Specification for Construction of Clean Operating Department of Hospital

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