Ultra-clean ventilation system performance

Review

Prevention of airborne and contagious infections during the surgery process is one of the most important necessities for more efficient and economical care to provide health and well-being of patients.This study examines the pattern of airflow related to ultrasonic ventilation systems based on surgical halls using computational fluid dynamics. 0 – 20 Pascals) with different spaces, acceleration and flow rate are discussed. The ultra-thermal ventilation system in spaces with positive pressure (20 Pascal) has a high performance and more efficiency, but for environments where there is no compressive difference between the surgical site and the surrounding spaces, the intention of this research is to find and discuss the ways to design the airflow system in operating rooms.

1.Introduction

Hospitals are host environments for a wide variety of microorganisms that have become a regular embellishment for patient transmission.These microorganisms are very dangerous for patients with deep wounds and those under surgery or those with immunodeficiency or severe immunodeficiency.About 10% of all patients have serious injuries as long as they are in hospital. they get infections. Some ways to transfer them are surgical equipment, medical equipment, physical encounters, food, beverages and aerosols.Bacteria transmitted by air can be distributed by ventilation systems or by unregulated air filtration into sensitive sites such as intensive care rooms or surgical halls. Patients in this place are usually in poor physical and mental condition with low level of immunity and defense, which causes fatal infections in some situations. Some specific surgeries such as implantation or organ transplantation extend this risk by penetrating infections, bacteria and microorganisms into the depths of wounds and the site of accession of a new organ or prosthetic limb. In addition to the health risk of infections, they cause a great financial burden during health services and services. As a result, reducing infections in surgery may have a positive impact on health and treatment costs.

1.1- Bacterial infections in hospitals:

One of the main ways to penetrate bacteria is the movement of human skin particles. Old and worn skin is constantly being replaced. Every minute of the day between 3,000 and 50,000 microparticles are released from the surface of the skin into the air, atmosphere and clothing. In case of disturbances in the body, this amount will be even greater.A large part of the dust in a variety of environments is caused by the skin of the body that can be easily detected in sunlight.

Most of these particles are between 5 and 30 microns, which are very suitable for the movement of bacteria, and the air also moves them to the point where they find a suitable place to stop, often on the horizontal surface, such as the earth, about 10 percent of these skin particles contain bacteria that are considered harmless under normal conditions, however if they are on surgical equipment or on the patient’s open wounds, landing with low safety levels After welding the injuries, most infections in deep wounds will be caused by aerosols carrying bacteria from the surface of the skin and cloth of medical equipment or the patient’s belongings or sources outside the surgical room. Other infectious organisms such as molds and hogs can also be found in hospital environments.

The number of these particles on the surface is estimated by multiplying the volume unit number at the surface sediment rate. Sediment rate is also estimated at 0.3 M/Min. بنابر این در سالن هایی با Colony Forming Unit)/ m3) CFU 100 ، 1800 CFU/m2/h بر روی سطوح افقی که شامل میز تجهیزات پزشکی نیز می شود تهنشین خواهد شد.

The problem of reducing the amount of contagion factors and particles in the air of surgical rooms due to the multiplicity of factors affecting the creation of such risks will be complicated.

Some of these factors include the architectural design of the building, medical equipment and protocols of facilitating devices.

The main factors affecting the three major broadcasts are divided into three main broadcasts:

1.Environment

• Architectural design of furniture and facilities
• Number and location of entrance roads and valves to surgical halls
• Build Quality
• Quality of building materials
• Special building facilities and capabilities including reduction of horizontal edges and use of spial paints
• Controlling the number of devices in critical range

2. Surgical procedure

– Controlling the number of devices in sensitive areas

• Open the opener protocol
• Items used in protective clothing
• Cleaning process

3.Fluid Mechanics

• Used ventilation systems
• Type, location and number of air filters
• Calibrating and controlling the ventilation system

A summary of bacterial infection problems is available in surgical rooms and halls collected in 1986. The amount of particles carrying the skin in a surgical salon is proportional to the number of items and supplies in the hall the number of times the entrance doors are opened, the surface of the skin that is exposed to the air, and the amount of long hair that is undated in the environment.

This study is based on fluid mechanics specifically for ventilation of ultrasonic halls. These ventilation systems are one of the most common in hospitals in the UK. Computational fluid dynamics (CFDs) models are defined for analyzing the airflow of systems, based on the surgical halls of JamesUniversity Hospital, sometimes used for orthopedic surgeries. In this model, the effect of reducing excess pressure in the hall, speed and acceleration of the inlet air, doors and entrance roads are investigated. This model is also used to demonstrate efficiency and enhance understanding of these systems as surgical procedures and opener protocols are key to reducing the amount of contagion factors in the future.

2-1: Ultratherming ventilation systems (Ultra Clean Ventilation:UCV)

An ultrasonic ventilation system, the air unit controls the amount of air flow in surgical halls. This model of airflow systems has been used in hospitals around the world since 1960. The first version of these systems was created atBataan Memorial Hospital in the United States.

Before using ultra-clean ventilation systems, conventional systems that included mechanical fans suctioned the air from the surgical rooms and halls. These systems generally have the right temperature and humidity by passing through hepa filters ( High Efficiency Particulate Air: High efficiency of air with particulate matter (dry filters with minimum efficiency for particle collection up to 99.97% and for heat particles DOP ( Dioctyl phthalate (or alternating rounds of 0.3 μm) is provided.The fundamental change that happened in relation to ultratherming ventilation systems is the definition of airflow (laminr) and uniformly received and increased air circulation rates. A report from the Medical Research Console (MRC examined 8,000 cases of joint replacement surgeries between 1975 and 1980, which showed a decrease in the amount of noise during the change from conventional operating room ventilation (3.4%) to the ventilation system of uniform flow of these places (1.2%).

Also, a controlled test was performed on patients who had joint transplantation surgery after surgery and their toxicity rates were performed in two different conditions of traditional ventilation and conventional and ultra-clean ventilation, which as a result of reducing the percentage of infectious poisoning in the use of ultrathermized ventilation systems. It shows UCV and suggests that if the concentration of bacterial particulate matter (BCP) on the wound does not exceed 10 BCP/m3 and in better and cleaner conditions that these particles are 1BCP/m3 or less, it will naturally benefit.

This shows that the main pressure of the system has a limit of 1%at the lowest rate of infectious and contagious agents. However these events are too high, given the risks to patients’ lives and high costs for fixing such infections, plus due to the special need that occurs during the increase in infectious problems Mrsa existing hospitals should make progress in this area to improve this system.

2- Fluid mechanics of surgical halls using ultrasonic ventilation system.

Photo Photo 1 is used to draw the mechanics of airflow fluids in surgical rooms and halls, comparing the representative of ultrasonic ventilation systems. The air accumulates in a clean area and during the entrance to the surgical table section in the diagram and becomes funnel-like and spreads near the surface and above the walls of the surgical hall. This shape describes a recursion. Discharge Speed (0.3 – 0.4 M/ The entrances should be enough to flatten the ambient air for surgery, but it should not be enough to create unsafe conditions for the equipment.In the ceiling, the air of the surgical hall is removed from the ceiling outlet (suction). The suctioned air (oxed) is combined with the initial filtered air and passes through the filters and the air inlet. This creates the required control for the number of times the air changes per hour. The primary filter has an efficiency of 45% and 95% in relation to particle collection. The air in the surgical room is retrieved by passing through the hepa filter. This type of continuously flowing cleaning removes harmful particles in the air. The inlet air is fresh and filtered, and the outlet air is a combination of exoplanet air and air that is imported from the cracks in the structure of the halls as well as the nearby seams in The amount of outlet air in the surgical halls is easily obtained from the sum of the desired environment for the exoskeleton and the cracks of the hall and the seams of doors and windows. At all times in hospital environments, the required pressure difference in different rooms varies from 9 to 30 Pascal. The positive pressure in surgical rooms should be about 20 pascals above the surrounding space to prevent filtered air from entering the surgical halls.

Entering unfiltered air into the surgical room is one of the most basic threats to the cleanliness of the system. If the volume of air entering the surgical hall is too low, the pressure in the surgical hall drops, and the air around these halls that have unfiltered particles will have a better chance of entering the surgical hall, which increases the risk of contamination. When the inlet and outlet air rates are properly balanced, the positive pressure creates a protective barrier that provides suitable conditions for fluid flow that continuously cleans the air of the room and the surgical hall from pollutants and pollutants.

In short, the fluid system is used to help provide clean air and create a comfortable environment in surgical halls during surgery. Generally, this action has been carried out with regard to three main objectives:

1. Particle reduction includes pieces of skin from surgical materials that have been removed from them. This goal is achieved by continuous recovery of internal air in the operating room by hepa filters that lower the rate of particulate matter to the lowest level, which is done by ultratherming ventilation systems.
2. Prevent unfiltered air from entering the communications around the rooms. This goal can be achieved by creating positive pressure in surgical halls that can control the inlet and outlet air of the operating room.
3. Considering the work rate and temperature comfort of surgical equipment as well as the patient.

This study investigates possible weaknesses in the fluid mechanics of the surgical room when positive pressure is not supplied, especially the impact of operating room entrance doors and roads, which may cause unfiltered air to enter, which includes higher particle rates.

3- Fluid Computational Dynamics Model (CFD: Computational Fluid Dynamic)

3-1) Introduction of CFD Dynamic Computational Fluids

Figure 2 shows the computational dynamics model of fluids used in the research. CFDis a program for numerical methods that is the solution of discrete models for determining the equation of fluid mechanics. This tool can be used to analyze and design high-rise buildings in the following areas:

• Contaminating content
• Temperature and humidity
• Outer wind pressure
• Indoor air quality
• Smoke Control
• Ventilation System

This type of analysis can bring results that have not been possible in the past.Using visual data programs, the results can be presented in an understandable way that reduces the costs and dating to acceptable results in the field of design.According to the analysis of the measurement operating room and calculations of the site and the simulated air in empty halls and free of surgical operations to The placement of rooms and halls during surgery was investigated. Since small technical weaknesses may cause false positive and negative results, frequent use of surgical salons may also make our assessment difficult. Hence, CFD is a common, low-cost test method. CFDbrings the finest details and information in all places with multiple parameters.

3-2) Geometric model

The cfdmodel is based on the operating halls of JamesUniversity Hospital. These sizes include 6.4 meters long- 5.6 meters wide and 2.9 meters high, and one double-walled entrance with dimensions of 1.6 meters wide and 2 meters high, which is the main entrance road. The main point of the CFDmodel is at the center of the intersection between the ground level and the entrance wall surface. The surgical hall has two pressure apertures on the walls, each with dimensions of 0.5 meters wide and 0.15 meters high. The pressure apertures embedded on the wall are located on either side of the doors and at a height of 0.2 meters above ground and at a distance of 1.5 meters on the ZXaxis. The main way of entering the air and the hepa air filter level is 3 meters long and 3 meters wide, which is located at the center of the roof surface of the surgical hall surrounded by a ceiling pressure aperture with a width of 0.1 meters.

Within the surgical hall there is a 0.9-meter vertical suspended margin around the air inlet. The CFDmodel includes a surgical table, patient, 6 equipment tables and 4 surgical personnel. Removable lights and lights that are usually present in surgical rooms are not included in this model, which is because the protective air barrier is more powerful in recent tests when the light is removed, so if the protective air barrier fails in the absence of light, it will definitely be rejected in the presence of light. As a result of this situation, it is a scenario to investigate the worsening conditions with the parameters tested. Furthermore, research by zoon and Loomans shows that a small 0.1 square meter lamp does not cause significant airflow disturbances.

The surgical table is located under the main air entrance and has a clean zone with a length of 3 meters, a width of 3 meters and a height of 2.9 meters. Air including surgical room waste should not enter this area at all. This action cannot be implemented through physical bounds and must be carried out by the creation of protective aerial dams.

This protective air barrier is supplied by using the inlet port of ceiling pressure holes and vertical margins and injecting filtered air non-directionally towards the surgical range from top to bottom with an approximate speed of 0.4-0.3 meters per second (National health service estates 1994 (which creates a curtain of air around the clean range)clean zone.

Basically, this method of workplace equipment protects the patient’s open wounds against the penetration of particles containing infections and contagion agents that have resulted from the freeness of skin particles and the operation of the equipment inside the surgical room.

3-3) Numeric network

CFDgeometry is examined based on surgical halls of JamesUniversity Hospital. The dimensions throughout the hall have been examined in previous sections. This model includes rectangular cube boxes representing internal compounds including surgical tables, patients, equipment tables and surgical personnel. Also, in this model, the upper edges of 0.25 meters, medical equipment 0.1 meters and upper edges from 0.3 meters to 0.15 meters are converted. The geometric dimensions related to the placement of compounds are described in Table 1. All locations are related to the points of the original model.

Smoke testing in empty operating rooms with closed doors and comparing full and half rooms in CFDmodels show that the airflow in the 0 M ZX circuits is equal. The surface equality of the center of the surgical table is divided into two geographical positions. Half of the surgical hall is also used as a model.

The numerical network used to network surgical halls is unorganized.This network is made of 6-node prisms and quadrangled agents with 4 nodes. Up to 5 layers of these prisms are placed at the inner level and the index wastes are networked with quadranglaters. The size of these networks is approximately 800,000 factors with internal domain, network level and number of charter layers in Table 2.

The study of independent networks shows that this network provides the appropriate density. Networking is completed using icem’s general trading program.

3-4) Solver Suppliers

Numerical analyses performed by the trade code CFX5.7 and the most common turbulence, reynold averaged navier strokes (RANS) model of K-ε with high resolution in the horizontal motion scheme of the aerial masses due to temperature change and with floating model have been performed. All models were common in sediment volume after approximately 150 repetitions.

The use of K-ε model and Turbulence model were selected as the basis in previous researches. In particular, the study conducted on the Two-Equation K-ε model and by comparing the results of the experience shows that the Re-Normalization Group (RNG) model has performed better than standard K-ε models in simulating airflow displacement, So progress has not been enough to ensure more expensive and costly calculations. In addition, these results are confirmed by Cook &lamas, which used CFX in buoyancy-driven ventilation flow displacement model. Finally, the simulation results of each pair of standard and RNG and K-ε models have been able to produce high-quality results compared to mathematical theories and salt baths.

The polluting dispersions in vast interiors under the same temperature conditions have been investigated. The Scale model that releases color in water is compared to the predicted CFD that uses the standard K-ε model. The results show that the composite flow design in the results illuminates the acceptable accuracy of the simulation. Cfd trading codes that employ the standard K-ε model have less efficiency in terms of numerical computational intensity than large simulated opposite currents.

Finally, it should be noted that the K-ε and Turbulence models have been successfully applied in a number of these operations-related researches. The conditions for creating boundaries for inputs were created using the speed and intensity of turbulence and chaos. These are estimates of the experience gained from james university hospital’s surgical rooms survey. Calculations report air velocity in the inlet valves approximately 0.3 m/s with a turbulence intensity of 10% (average turbulence intensities between 8% and 12%). These measurements with speeds of 0.2 m/s and 0.4 m/s were used in CFD analysis model.

The bound conditions for both exester outputs were adjusted according to the mean static pressure. This model investigates the effects of ultra clean ventilation system in this study. The wall output pressure is set to 0 Pa, as well as the ceiling output pressure on 0 Pa, by simulating the same pressure in the operating room associated with the connected rooms and then set to 20 pa to create the same atmosphere with positive pressure in the operating room.

The conditions of the boundary of the doors are divided into two lower and upper sections. In the lower part, the airflow speed shows U m/s, which decreases to 0 m/s at an altitude of 0 m to 0 m/s. Around the neutral axis, the output flow rate increases to 0.9 m (the volume equal to the inlet airflow rate at an altitude of 1.8 m is known as U m/s). This mechanism is based on smoke testing performed by blowers and crews.And in this review, each pair of entrance doors is open. A smoke generator above each door directs the airflow outwards. As long as the smoke generator is moved down and near the earth’s surface, the volume of airflow decreases. And approximately in the middle half of the distance between the top and bottom of the door, the flow fails and in addition to the lower levels the inlet airflow increases.

This rebuilds and peer-to-peer a possible scenario that may replace situations where doors are open. Four scenarios based on the volume of inlet and outlet airflow with speeds of 0, 0.1, 0.2, 0.3 m/s are separate models that are visible in figure 3. The factors affecting these scenarios are different in terms of fluid temperature, density, and middle pressure of surgical rooms and outer space.

A person entering the room through the entrances carries a certain volume of air, especially in the back of his head, which is equivalent to 100 times the opening of the entrance to the operating room during the operation, in addition to the time the door can be opened, for example, to transfer equipment. Opening the doors with a person’s movement to become a model is a complicated task. This may include a fleeting model that meets the conditions with the doors open and then receives the entrance, followed by closing the doors.

Recent research examines the movement of doors and the impact of human movement on displaced devices. The results show that human movement increases the displacement of the part to the transitional particles and this amount depends on the type of doors. Although studies on operating room inputs have not used the door control system, there is no doubt about the relationship between the duration of the openness of the entrance doors. The difficulty and capability of design should not affect the intellectual limits of the end users. This is especially important when the end user is doing complex tasks.

Therefore, the protective air barrier must operate independently against the entrance doors. Considering all these conditions, we selected the steady state model for investigation. This is a test for the protective air barrier of the entrance doors and the placement of medical equipment. It seems logical to declare that the stable conditions model has almost the worst of this scenario due to the existence of continuous airflow in proportion to the uns stable airflow in a short period of time.Finally, this study shows the results that show the effect of input and output doors.

The summary of the types of bound conditions discussed in this study is shown in Table 3. The temperature in this model is set to 25 degrees according to the temperature conditions of James University Hospital and a temperature model for knowledge in CFX solver has been selected.

3-5) Validity and Verification

Annual surgical measurements were performed based on the model and conditions of James University Hospital and these were used in confirming the CFD model. Air speed is measured by an all-directional wind meter. The wind meter sensor is strapped on one of the tripod arms to measure the slightest lack of turbulence according to the flow space.The sensor veck is placed on each node with a 2-minute interval. One minute is enough to pass the aerial disturbances caused by the tripod shift, so the next minute is used to collect air speed data. This technique is acceptable for previous computational motion conditions. The wind meter’s electric analog output is connected to an information recorder that records air speeds at intervals of one second. This makes it possible to measure and estimate the intensity of turbulence. Smoke testing has also been carried out to estimate the flow of air direction.Photos taken with a network background have been used to help detect the flow direction used. Simulation results in occupied area were compared with On-Site measurements. These data points are located at 2.7 m of YZ axis and 0.3 m of networks starting from XYZ axis with 7.2 m, 15.3 m, 0.05 m, respectively.

Experimental and numerical predictions showed a difference of less than 17% with the results indicating that the complexity of the studied physical conditions was acceptable.

4. Reviewed Cases

Two conditions have been examined with the equipment and settings of the models ahead:

• Positive pressure model: Ideal conditions are set to 20 Pa with ceiling pressure output and partial conditions. These conditions simulate the positive pressure of the operating room associated with the side rooms. The door attached to the operating room in this model is open and the protective barrier as well as the air of the surgical halls are continuously being retrieved by passing through hepa filters.
• Equal pressure model: In this situation, the ceiling output pressure is set to 0 Pa which simulates operating room environments with equal pressure attached to adjacent rooms. In this model, the operating room doors are open and the protective barrier as well as the air of the surgical halls are continuously being retrieved by passing through hepa filters.

As discussed in previous sections, 3 different limits for airflow on the inlet and 3 boundaries are used for open doors and one for exit doors, which evaluates the system’s ability to keep particles away from clean zone. These results are generally evaluated in 24 cases in Table 4. (Combinations of limit conditions and model settings)

5- Results

Streamline effect of lines that reduce air resistance is used in different parts of operating rooms to evaluate the efficiency of protective dams. A streamline is a constant flow that particles with zero volumes will take over and move along its sphere.In this study, lines are considered as starting point for multiple streamline algorithms for testing the most relevant and for the efficiency design of protective dams.

The first streamline groups of surgical halls are located outside the clean zone and away from the doors. Visible in Figure 5. The geographical location of the error starting points is located in Table 5. These are used to evaluate the capabilities and capabilities of protective barriers to prevent gaps in clean zone from the operating room interiors. In all 24 studies, streamlines were not entered into Clean Zone. The dam is not broken and each streamline is finished at surface and wall outlets. One type of all these results is displayed for 20 items in Figure 6.

The second type of streamlines (doors) are located outside the clean zone and right in front of the door. The geographical location of the starting point at the start of the lines is shown in Table 6 and in Figure 5.

These are used to assess the ability of protective dams to prevent gaps in clean zone from the outer site of the surgical room. In all models studied with positive pressure model, streamlines have not entered the Clean Zone. However, the number of cases in which the equal pressure model is used (when the inlet airflow from the doors has a speed of 0.2 and 0.3 meters per second) the protective barrier has been broken as visible in Table 7. Streamlines pass under the surgical bed and between the surgeon and the patient. Therefore, during the surgery, the airflow is contaminated and there is an infection to the wound site. The results of case number 16 (image 7 and 8) and case number 24 (figures 9 and 10) depict the failure of the protective barrier against particle penetration.

The fracture mechanism is divided into two parts: the first part consists of particles entered into the Clean Zone from the doors, resulting from the amount of airflow movement within the boundary. It can be shown circularly in figure 11 on the XY axis in mapping (0.2 m). Due to the airflow coming from the main entrance and passing through the devices with a zealous edge, including rectangles representing the patient’s model and surgical equipment, the shape of fluid movement is circulated under the surgical table. (In Figure 12)

The shape of the circulation again in the second part of the failure mechanism consists of particles transported in the direction of the X axis under the surgical table. These particles may move towards the wound range with the opposite flow, about the layer around the patient, the surgical table and medical equipment.

6)Discussion

According to the results of this research, when positive pressure is established in the operating room, the probability of air with particulate matter entering the operating room is minimized.

The presence of doors in the operating room is effective on the airflow system, the main effect of this action is to reduce the positive pressure in the operating rooms. That may even lead to 100 times opening and closing during surgery. Therefore, opening the door continuously may eventually cause the system to fail. This may also be exacerbated by the inability to communicate positive pressure. Due to the inability to establish positive pressure, this failure to penetrate the air including particles from the entrance doors that penetrate the protective barriers and then enter the clean zone and pass through the space between the surgeon and the patient, which increases the risk of infection during the surgical procedure on deep wounds.

In this study, the doors are located on the ZX axis of the surgical room, so the air containing the particles is transferred from the doors directly through the doors to the Clean Zone. So the doors should be moved to the corners of the room, which reduces the intensity and volume of inlet airflow to clean zone. However, changing the location of the doors reduces the speed of transfer of tables, medical equipment and patient transfer by personnel. As a result, most of these methods are not suggested.

The effect of increasing the distance between the clean zone and the inlet doors on the XZ axis can be investigated, which reduces the instantaneous movement of particles transported by the inlet airflow to the clean zone. It is important to point out that in these studies the impact of openness of only one input has been investigated. While in many surgical rooms there is more than one in. Opening these doors all together and at the same time certainly significantly increases the risk of protective barrier failure since the internal pressure of the room decreases considerably with each opening and closing door.

The addition of a clean ultra aisles to operating room entrances has been used in a number of hospitals, and in these environments, the air in the ultra-clean corridors is filtered by passing through hepa filters. Therefore, the air near the doors, which are easily entered into the operating room by airflow or the movement of personnel and equipment, minimizes the possibility of creating infectious diseases.

In the field of surgery, due to the length and complexity of the operation and the number of personnel and equipment entering the door, it should be opened and closed. Therefore, a positive pressure in operating rooms that is approximately 20 pascals higher than the pressure in adjacent rooms should be established in surgical sites. This may be achieved by controlling the output pressure and air traffic added to the system. In the clean room laboratory environment, this system has been successful.However, the process of working in operating rooms will be very different from the laboratory conditions. Operating room work may be in a state of emergency for a long time, so operating rooms should be designed for operation despite the high number of doors opening in short and long periods of time. This may be achieved by using a clean ultra aisle system, reducing the entrance doors, checking the geographical location of the operating room and air conditions control system.

7- Result

This study investigates the airflow forms of ultra-clean ventilation system (UCV) based on the use of operating room CFDs. The effect of opening and closing doors in two scenarios of 20Pa and 0 Pa pressure with inscribed space of different inputs and inflow speed of doors has been investigated.

The UCV system operates appropriately in the 20 pa positive pressure scenario, but fails as long as there is no difference in pressure between the operating room and the surrounding spaces. The concept of this research has been to find and discuss the design guidance and air flow system of surgical rooms. The main design proposal is related to the geographical conditions of the rooms and operating halls. The main input speed cannot be increased to maintain the temperature comfort associated with surgical personnel and equipment, and it is always necessary to be careful to maintain sufficient distance between the doors and the limits of the clean zone. The use of ultrasound corridors to reduce the concentration of bacteria-transporting particles in nearby areas is also suggested.

The standard K-ε turbulence model is used for CFD analysis and is successfully identified as a model for the first failure mechanism. (e.g. defects in the protective air barrier)

In the future, more synthetic turbulence models such as the Large Dimension opposite Current Pseudo-Maker (LES) model may be needed to investigate the more complex interactions within protective aerial dams and the impact of human activity on the displacement and transport of transporting particles.

Resources

Allen P, Reynolds DA (1978). Clean Air Operating Environments. British Journal of

Hospital Medicine.

Bennett MD, Brachman MD (1986). Hospital Infections, 2nd edn. Boston: Little,

Brown and Company.

Blowers R, Crew B, (1960). Ventilation of Operating Theatres, Journal of Hygiene, 58:

427-448.

Brohus H, Hyldig M, Kamper S, Vachek UM (2008). Influence of disturbances on

bacteria level in an operating room. Paper presented at the 11th International

Conference on Indoor Air Quality and Climate, Copenhagen, Denmark

Brown AR, Taylor GJ, Gregg PJ (1996). Air Contamination During Skin Preparation

and Draping in Joint Replacement Surgery. Journal of Bone and Joint Surgery –

British Volume, 78(1): 92-94.

CFX (2001). CFX 5.1. Flow solver user guide. UK: Harwell Laboratory.

Charnley J (1964). A clean-air operating enclosure. British Journal of Surgery, 51: 202–

205.

Chen Q (1995). Comparison of different k–e models for indoor airflow computations.

Numerical Heat Transfer, Part B, 28:353–69.

Choi JI, Edwards JR (2008). Large-eddy simulation of human-induced contaminant

transport in room compartments. Indoor Air, 18(3):233-49.

Choi JI, Edwards JR (2012). Large eddy simulation and zonal modeling of humaninduced

contaminant transport. Indoor Air, 22(1):77-87.

Chow TT, Yang XY (2003). Performance of ventilation system in a non-standard

operating room. Building and Environment, 38(12), 1401-1411.

Cook MJ, Lomas KJ (1998). Buoyancy-driven displacement ventilation flows:

evaluation of two eddy viscosity turbulence models for prediction. Building

Services Engineering Research and Technology, 19(1):15–21.

Finlayson EU, Gadgil AJ, Thatcher TL, Sextro RG (2004). Pollutant dispersion in a

large indoor space. Part 2: Computational fluid dynamics predictions and

comparison with a scale model experiment for isothermal flow. Indoor Air,

14(4), 272-83.

Hambraeus A (1988). Aerobiology in the operating room—a review. Journal of

Hospital Infection, 11: Supplement 1, 68-76.

Hirsch C (1991). Numerical Computation of Internal and External Flows, VolumeSpringer-Verlag.

Hoffman PN, Williams J, Stacey A, Bennett AM, Ridgway GL, Dobson C, Fraser I,

Humphreys H (2002). Microbiological commissioning and monitoring of

operating theatre suites. Journal of Hospital Infection, 52: 1–28.

Lidwell OM, Elson RA, Lowbury EJL (1987). Ultra-clean Air and antibiotics for

prevention of postoperative infection. A multicenter study of 8052 joint

replacement operations. Acta Orthop Scand, 58: 4–13.

Lidwell OM, Lowbury EJL, Whyte W, Blowers R, Stanley SJ, Lowe D (1982). Effect

of ultraclean air in operating rooms on deep sepsis in the joint after total hip or

knee replacement: a randomized study. British Medical Journal, 285:10–14.

MacDonald DA (1995). The Infected Joint Replacement: Prevention, Diagnosis and

Treatment. Current Orthopaedics, 9: 21-27.

National Health Service Estates (1994). Health technical memorandum 2025:

vent