Solution to Construction of Negative Pressure Isolation Ward
In recent years, the construction of negative pressure isolation ward has developed rapidly in China, but there are inevitably some problems in the design and construction of negative pressure isolation ward because there has been no standard of negative pressure isolation ward in China in the past. Taking the whole negative pressure isolation ward of a hospital in Xi'an as the object of pollution control and isolation, this paper completes the air conditioning design of the isolation ward of the hospital by combining the reasonable layout and partition, the pressure difference control between adjacent areas and rooms, the reasonable configuration of filters and the control of air distribution.
Building Plane
Focusing on the core design idea of taking the whole negative pressure isolation ward area as the object of pollution controlled isolation, following the design principles of "functional conformity, short process, clear cleaning and reasonable partition" in the plane layout, the following consensus was reached after repeated communication with the hospital:
1) Negative pressure isolation ward is set at the southeast end of the ward independently, and it is a self-contained area to minimize interference and facilitate isolation and management.
2) Negative pressure isolation wards are designed as double rooms. Each negative pressure ward is equipped with a buffer anterior room and a bathroom separately. It also includes corresponding auxiliary rooms such as medical corridor, doctor's office, treatment room, nurses'station and sewage and disinfection room. The ceiling height is 2.8m.
3) The whole isolation ward was divided into semi-polluted area and polluted area. Medical staff, patients, clean goods and dirt are moving towards science and rationality, eliminating any cross-infection and embodying the characteristics of humanized design.
Semi-polluted areas include buffer zone between ward and inner corridor, corridor for medical staff, treatment room, doctor's office, nurse station, etc.
Contaminated areas include isolation wards, bathrooms, patient corridors and sewage and disinfection rooms. In the past, isolation wards were generally divided into three areas, i.e. contaminated area, semi-contaminated area and clean area. The clean area mainly includes medical corridor, doctor's office, treatment room, nurse station and other auxiliary rooms. However, the clean area of the negative pressure ward mainly refers to the areas other than isolation wards, and there is no clean area in the interior of isolation wards.
4) Buffer rooms are set up between the corridor and the corridor to the outside in different areas, which can reduce the pollutant diffusion caused by the dynamic change of temperature difference in personnel, door switches and connecting rooms, and greatly improve the dynamic isolation ability. As can be seen from Fig. 1, buffer corridor 1 and buffer corridor 2 are respectively set between patient corridor, medical staff corridor and clean area outside isolation ward, and buffer rooms are set between each ward and medical staff corridor.
Fig. 1 Isolation ward plan
5) Except for fire safety doors, all doors in the area are opened to the side with high pressure, which can increase the closeness of the doors. The opening direction of the door is determined according to the degree of contamination inside the isolation ward. For example, the toilet door should be opened to the side of the ward door. This paper mainly refers to the requirement that the closed door of the clean room should be opened to the room with higher air cleanliness in the Code for Design of Clean Workshop. The fire evacuation door must meet the fire protection requirements and open in the direction of the evacuation channel.
6) The location design of negative pressure isolation ward takes full account of natural lighting, and then uses the permeable glass partition, which can alleviate the depression and anxiety of patients to a certain extent, and contribute to the treatment effect. In general, patients need to stay in the isolation ward for a period of time, during which the patient's emotions have a great impact on the effect of treatment. If the patient has been depressed and restless, it is not conducive to recovery. For this reason, natural light and even natural landscape are fully utilized in the location design of six negative pressure wards, and 2.8m ceiling height is also considered.
air conditioning system
Indoor and outdoor design parameters
In summer, the dry bulb temperature is 35.2 C, the wet bulb temperature is 26 C and the atmospheric pressure is 95 920 Pa; in winter, the outdoor temperature is - 8 C, the relative humidity is 67%, and the atmospheric pressure is 97 870 Pa.
The indoor design temperature and relative humidity of air conditioning in polluted and semi-polluted areas are 24-28 degrees C and 45-65% in summer, 18-22 degrees C and 35-55% in winter.
Classification of Air Conditioning System
Air-conditioning systems are set up in semi-polluted and polluted areas respectively: six negative pressure wards adopt one drag-and-pull mode, each of which adopts a set of all-air system; semi-polluted areas adopt a set of all-air system independently; patients corridor only considers exhaust system; 4, 5 and 6 negative pressure wards need to switch to fresh air operation (air-conditioning system schematic diagram) See Fig. 2. The number of ventilations in the air treatment unit is shown in Table 1 to meet the needs of isolating patients with severe infections.
Fig. 2 Principle diagram of air conditioning system
Table 1 Air handling unit ventilation times
Performance and Characteristics of Air Conditioning System
1) The air-conditioning system adopts the whole air system, which can avoid the secondary pollution, leakage and noise caused by the accumulation of condensate water compared with the fan-coil unit used in the ceiling.
2) Six negative pressure wards all adopt the form of one drag and one drag. Each negative pressure ward circulates independently. It is not only more flexible and energy-saving, but also can avoid or reduce cross-infection among patients.
3) The air conditioning system runs for 24 hours, and the air volume at night can be switched to low gear operation, so as not to disturb patients'rest.
4) Negative pressure wards 1, 2 and 3 adopt self-contained fresh air and can be switched to fresh air supply to meet the needs of treatment and isolation of patients with severe infections.
5) The air conditioning unit adopts single-inlet centrifugal fan to meet the requirements of small air volume and high static pressure.
6) Interlocking control of air conditioning unit and exhaust fan.
7) The patient corridor is only equipped with exhaust system, without considering air conditioning system, in order to achieve the purpose of energy saving.
8) The air supply outlet is arranged on one side of the room, opposite to the hospital bed, so that the medical staff are on the upper side of the wind, and the exhaust air is discharged from the side of the hospital bed.
Air conditioning control measures
The air conditioning control measures needed for negative pressure isolation wards are mainly from the following aspects: pressure difference control between different districts; physical method of air filtration to effectively remove bacteria and viruses in the air to feed clean air; indoor air distribution and air supply volume to dilute and remove indoor pollutants.
1) differential pressure control
The main purpose of pressure difference control is to prevent pollutants from diffusing from polluted area to clean area, to form reasonable airflow and directional flow between polluted areas, and to achieve by adjusting the difference between supply air volume, return air volume and exhaust air volume (the design value of pressure difference is detailed in Fig. 1). As can be seen from Fig. 1, except that the buffer corridor 1 and 2 connected with the clean area maintain 10 Pa positive pressure, the rest of the rooms are negative pressure.
The degree of negative pressure from high to low is toilet, negative pressure isolation ward, patient corridor, buffer room, medical corridor, doctor's office. It is also different from the design of negative pressure ward in the past. The whole negative pressure isolation ward area should be taken as the object of pollution controlled isolation. On this basis, pressure difference control is carried out, which is more conducive to preventing the diffusion of pollutants. In adjacent places where pressure difference is required, a micro-pressure differential meter shall be installed at the visual height of the connected doorway.
2) Air filtration
The air supply in negative pressure isolation ward meets the requirements of DN11/409-2007 "Indoor Air Hygiene Quality Requirements of Hospital Infectious Diseases Section". Ultra-low resistance and high efficiency filters with initial resistance of only 20 Pa are used in the air supply outlet, and high efficiency filters are installed in semi-polluted area and buffer room (60 H-1 air exchange times in buffer room). The return air and exhaust air in the negative pressure isolation ward and the exhaust air in the toilet are equipped with safe and removable zero leakage and high efficiency return air device. The return air outlet in the auxiliary area of the negative pressure ward, i.e. the semi-polluted area, is also equipped with ultra-low resistance and high efficiency filters.
3) Air distribution
Negative pressure isolation ward adopts upper and lower side air flow organization. Indoor air supply first passes through medical staff and then flows to patients. Finally, it is discharged by exhaust outlet to form a directional and reasonable air flow, so as to ensure the rapid and effective removal of pollutants exhaled by patients. Dead zone, stagnation of air flow and short circuit of air supply and exhaust should be avoided as far as possible. At the same time, comfortable rest environment should be provided for patients and healthy working environment should be provided for medical staff. The main air outlet of the ward is located on the roof of the medical staff station beside the bed, and the secondary air outlet is located on the roof of the tail of the bed. Because it is a double ward, the air outlet is arranged between the two beds, which is conducive to controlling the spread of pollution.
In view of the characteristics of air-borne infectious viruses, the idea and characteristics of using the whole negative pressure isolation ward as the object of contamination controlled isolation are put forward, and the measures of reasonable layout zoning, pressure difference control between adjacent areas and rooms, reasonable configuration of filters and control of air distribution form are combined. Implement measures to improve the isolation capacity of negative pressure isolation wards.
Source: HVAC
Author: Xiang Xiaoqiang, Sichuan Jianyang Gangtong Group Co., Ltd.
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