Chapter 5 Clean Room Design By the end of this chapter, you will be able to: l Explain the terms positive and negative pressure l Name and describe two categories of air flow in a clean room l List the main design features of a clean room l Explain the different grades of clean rooms Introduction In this chapter we will look at the specific design of a clean room including the walls, ceilings and floors as well as the practical needs of items such as workbenches, storage cupboards and chairs. We will examine how air is filtered to maintain the air quality and how air pressure prevents contamination of the cleanroom when people and equipment move into or out of the clean room. We will also take a brief look at the different types of clean room using particle counts to grade areas. Chapter 5: Clean Room Design 1
Aseptic Processing What is a Clean Room? Cleanrooms are usually self-contained facilities with their own dedicated ventilation systems. These control air quality, temperature and humidity. Air is filtered through High Efficiency Particulate Air (HEPA) filters which have a very small pore size. The filters collect and remove small particles, before air enters through the ceiling grilles. Ceiling HEPA filter Dirty air from the surrounding area is prevented from entering the cleanroom by controlling the air pressure in the cleanroom. l Cleanest room at highest pressure l Air flows from the cleanest to dirtiest areas Operation is at positive pressure, so ensures any airflow is pushed outwards from the room and dirty air cannot enter the room by default. The size of the aseptic suite depends on the maximum number of people who might use it at any one time. A fairly large room is more pleasant to work in, and the overall level of microbes in the environment is less affected by local air disturbances or contamination produced by individual workers. Clean Room Design Clean rooms fall into two categories, unidirectional and non-unidirectional. Build up of contaminants in the cleanroom is prevented by the flow of clean air at a rate of a minimum of 20 room air changes per hour. Unidirectional clean rooms normally have vertical airflow. Air flows downwards through HEPA filters located in the ceiling. The air is extracted through perforated flooring or grilles mounted on the walls at floor level. Note: airflow in a unidirectional clean room can also be horizontal. 2 Chapter 5: Clean Room Design
Chapter 5 Clean Room Design Non unidirectional clean rooms have air flows from HEPA filters located in various positions and returned through opposite locations. Filters may be distributed at equal intervals throughout the room or grouped over critical areas. The distribution and returns in this instance mean that the air flow may be turbulent in nature. The floors, walls and ceiling should be made of a smooth impervious material to ensure no particle shedding and easy cleaning. They should also be chemically resistant. All joins in the covering materials should be welded to ensure that there is no chance of seepage of cleaning fluids under the covering. Doors should be easy to open and, where necessary, two doors linked together to form an air lock. This prevents a sudden rush of air when a door is opened. All doors should be controlled to prevent unwanted flow of air from one area to another by opening of doors simultaneously. Benches should be made from one complete sheet of laminate because some liquids attack the adhesive at the joints and eventually cause lifting. Where possible made they should be made from stainless steel, Trespa or Conan which are impervious. They are usually wall-mounted to reduce dust collection and facilitate its detection and removal. When storage space is required, cupboards are preferable to drawers because they are easier to clean. Cupboards should be dust proof and smooth inside. Rounded beading may be used to cover dust-retaining angles within storage spaces and between fixed benches and walls. Small units on castors make useful additions to the working surface. Chairs must be adjustable and comfortable and covered with an impervious washable material. Trolleys should be made from stainless steel and be easily cleanable. Switches and sockets should be flush fitting and have plastic fingerplates. There should be no l shelves, window ledges or door frames where dust might settle. l pipes or ductwork. (False ceilings should be fully sealed with lighting recessed). l sinks or drains. Chapter 5: Clean Room Design 3
Aseptic Processing Hand washing facilities should be available external to changing rooms. Taps should be elbow or foot operated so that cleaned hands are not used to turn the water off. Soap should be conveniently dispensed from a wall or bench dispenser. Electric hand dryers or high quality paper towels should be used to dry hands. Remember: In summary, there should be: l smooth impervious surfaces l no ledges for dust to gather l surfaces which are easy to clean l transfer systems/airlocks to prevent contamination l no water sources Other aspects of design of the Cleanroom When designing a clean room there are many considerations to make. Here are a few but this is not an exhaustive list of good and bad practice. There should be a separate two-way transfer hatch system for the transfer of goods in and out of the cleanroom, to prevent contamination of environments. Material used in the construction should make cleaning and disinfection easy. For example there should be no joins between walls, floors and ceiling and all surfaces should be smooth and easy to clean. There should be a support room from which materials can be passed into and out of the cleanroom through hatches. Horizontal surfaces can accumulate particles and should be maintained by regular cleaning 4 Chapter 5: Clean Room Design
Chapter 5 Clean Room Design Airlocks should be installed between clean areas and adjoining dirty areas This is a close up of a high quality door and hinge. Glass is easily cleanable and enables safe access/egress. Equipment should not reduce the airflow and should not be placed anywhere it disturbs the airflow. This image shows an alcohol extraction unit situated in the spraying in zones of the preparation area. It works as a vacuum extracting the alcohol fumes. Many of the normal routes out of an aseptic suite can be difficult to access during a fire alarm due to the number of corridors out of the suite. This is an example of a specially constructed fire escape to the outside of the building from an aseptic suite. The outer door is fabricated as a standard fire escape door, however it is sealed behind a sheet of breakable glass. Chapter 5: Clean Room Design 5
Aseptic Processing Remember: Here are some other important considerations about the design and use of clean rooms. l The equipment should be arranged to minimise the amount of operator movement while maximising their comfort. l The number of staff in an aseptic processing room should be kept to a minimum. l The flow of personnel should be limited to minimise exit and entry especially in the critical area. l The number of transfers to the critical area of the clean room or isolator should be minimised. l Excessive movement adjacent to the critical area should be restricted. Test Yourself Can you list 10 features to take into consideration when designing/fitting out a cleanroom? 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 6 Chapter 5: Clean Room Design
Chapter 5 Clean Room Design Environmental Control The highest standard of environmental control will be included in the design of the clean room. Processes should be designed to give optimal personnel and product flow through the unit. We will look at this in more detail later. Aseptic processes in the clean room are designed to minimise the exposure of sterile components to the potential hazards of the manufacturing process. There are a maximum number of particles of different sizes allowed in the clean room at rest and during operation. Grade Particle size at rest Particle count (max particle /m3) Particle size in operation 0.5 µm 5 µm 0.5 µm 5 µm A 3,500 1 3,500 1 B 3,500 1 350,000 2,000 C 350,000 2,000 3,500,000 20,000 D 3,500,000 20,000 Not defined Not defined The table shows the values for the maximum particle count for different particle sizes within the different grades of clean room (Reference: Orange Guide 2007) Examples of Cleanroom Grade Grade A Laminar air flow cabinets and isolators, i.e. the point of fill. Grade B The aseptic room. Grade C The preparation room inner support room. Grade D Support, filling and isolator rooms. Information: Isolators may be sited in Grade C or D rooms check your local procedures). Chapter 5: Clean Room Design 7
Aseptic Processing Alarm Systems Fire and smoke alarms must be fitted in all areas of the facility. Staff must respond to alarms by evacuating the area immediately. An air supply alarm should be fitted which detects if there is a failure in the air supply to the facility. If this is triggered, work must cease immediately. In this simulated image the red lamps would indicate a problem with the cabinets. Work should only restart when the air supply has been reinstated and been running constantly for a minimum period. In the absence of a validation exercise of the cleanup time, this period should be one hour. Here is an example of an alarm panel with lamps showing the working status of the LAFC and Isolator cabinets. The green lamp indicates that the cabinet is running correctly in this image. Malfunctioning and Problems Problems should be reported immediately so that appropriate action can be taken. Anything unusual should be reported even though it may seem trivial, as it could be a precursor to a major fault or incident. You should report any procedural deviations or difficulties. Reports may be filed with the Estates Department at the hospital for any routine work that may need to be done within the cleanroom or supporting areas. Specialist cleanroom companies may be required to carry out more complicated tasks. Air pressure The air pressure in clean rooms is highest in the aseptic filling room ( cleanest ) and drops incrementally to the corridors. The usual practice is to start at 45 Pascals and come down in 10 Pascals increments, with the final differential being at least 15 Pascals. This will depend on the layout of your clean rooms. 8 Chapter 5: Clean Room Design
Chapter 5 Clean Room Design Clean Room Suite Layout The following plans are examples of clean room suite layouts for Isolators and LAFC s and show the flow of work and air. Airflow direction Workflow direction Step over Bench Transfer Hatches Isolator Suite Layout Laminar Air Flow Cabinet (LAFC) Suite Layout Isolator EU grade A LAFC EU grade A Clean Room EU Grade D Clean Room EU Grade B 2nd Change Room EU Grade D at rest 2nd Change Room EU Grade B at rest Inner Support Room 1st Change Room Outer Support Room Inner Support Room EU Grade D (clean room) Outer Support Room 1st Change Room EU Grade D at rest Chapter 5: Clean Room Design 9
Aseptic Processing Activity Make a sketch plan of your unit and mark on it: l Flow of products l Flow of people l Flow of documents l Air pressures in different parts of the unit. 10 Chapter 5: Clean Room Design
Chapter 5 Clean Room Design Questions Q1 What is the maximum allowable number of particles in a Grade A and Grade B clean room at rest and in operation? Complete the table below to show your answers. Grade A At rest In operation Particle size: 0.5 μm 5 μm 0.5 μm 5 μm Max number of particles allowed: Grade B At rest In operation Particle size: 0.5 μm 5 μm 0.5 μm 5 μm Max number of particles allowed: Q2 Why are airlocks installed between clean areas and adjoining less clean areas? (2) Chapter 5: Clean Room Design 11
Aseptic Processing Q3 What s the difference between a unidirectional and a non-unidirectional airflow? (6) 12 Chapter 5: Clean Room Design