Chapter 6
Work Zones
By the end of this chapter, you will be able to: l
l
l
l
l
Name and explain the differences between the types of work zones used in aseptic preparation Define the terms horizontal laminar air flow (LAF) and vertical laminar air flow Explain the advantages of using transfer chambers in isolators Name the types of contamination that can be found in the work zone List some of the do’s and don’ts of positioning in LAF Cabinets
Introduction In this chapter we will look at the different types of work zones used in aseptic preparation and briefly explain each one. This includes how the air is circulated and how we should work within these zones. There is also a quick reminder about work zone contamination.
What is a Work Zone? A work zone is the term we use to describe the area where aseptic preparation is actually carried out – in the laminar airflow (LAFC) or isolator cabinet. The laminar airflow cabinets (LAFC) and isolators are specially designed work zones with super clean air.
Laminar Air Flow Cabinets (LAFC) Laminar air flow cabinets (LAFCs) are used during aseptic processing to protect both products and components from contamination during the manufacturing process. As the name suggests, it does this by using a laminar flow of air. Laminar flow is the unidirectional flow (i.e. the air flows in one direction) of clean, filtered air over a critical work space. It can help to provide super clean areas for the critical production process. Chapter 6: Work Zones
1
Aseptic Processing
Laminar Air Flow Cabinet
Isolators Isolators are a clean environment in themselves, however they should also be sited within a clean room. HEPA filtered air is delivered into the work zone of the isolator. Isolator
Envair HLF Range Laminar Air Flow Cabinet
There are two types of laminar flow:
Cytotoxic Dispensing Isolator CDC-F Range from ENVAIR
Horizontal laminar flow is when the filters are at the back of the unit and the air streams over the critical zone towards the operator.
Cytotoxic Dispensing Isolator CDC-F Range airflow diagram from ENVAIR
Vertical laminar flow is when the filters are above the work surface and force clean air downwards in parallel streams. This type of flow offers some operator protection for the handling of some hazardous preparations. Information: LAFCs should be left running at all times. Clean up times after interruptions, i.e. power failures, should be validated.
2
Chapter 6: Work Zones
Isolators have several advantages over conventional cleanrooms in that they can be sited in a lesser grade of environment and a lower level of protective clothing is required. Isolators act as a physical barrier between the product and the operator, giving greater operator protection than LAFCs. Airflow may be unidirectional or turbulent with the object of removing contamination from work zone.
Chapter 6
Work Zones
The most commonly used isolators are either Positive Pressure or Negative Pressure Isolators.
Positive pressure
Task Check your local SOPs to find out which type of isolator is used in your workplace.
Protects product and operator
Isolator air flow and pressure
Used in the preparation of CIVAs, and may be recognised as the sleeves are blown outwards
Airflow and air change rate within the isolator should be monitored continuously. Input and/ output airflows are monitored continuously and alarmed to indicate when the flow is outside defined limits. The air change rate in all parts of the isolator system must be sufficient to maintain the defined grade of environment during use. Pressure differentials and direction of airflow are maintained. For positive pressure isolators, a minimum alarm pressure differential of 20 Pascals is set between the Grade A controlled workspace and the background environment.
Negative pressure Greater operator protection, but less protection for product Used in the preparation of hazardous products such as Cytotoxics, and may be recognised as the sleeves are drawn inwards
Isolators should be designed to allow leak testing and particle counting to be carried out in the isolator and associated transfer chambers without compromising the internal environment. Information: Refer to Chapter 10 Environmental Monitoring for more details on isolator leak tests. Isolators should be tested and maintained at regular intervals in accordance with manufacturers’ instructions.
Chapter 6: Work Zones
3
Aseptic Processing
Isolator Transfer Hatches
Isolator Gloves
Starting materials are passed into the isolator through a transfer chamber. Transfer chambers are designed to avoid compromising the controlled workspace of the isolator during transfer of components and should also protect the operator from exposure to air that is potentially contaminated from inside the isolator. The transfer chamber usually has its own HEPA filtered air supply.
l
The operator gains access to the isolator via a glove/sleeve system.
l
The cuff piece allows for easy, safe aseptic glove changes.
l
The glove and sleeve arrangement allows gloves of an appropriate specification, particularly with respect to perforations and pinholes, to be used. A fresh pair of sterile gloves of the appropriate size and material must be fitted for each operator working session.
Important: When working in isolators, care should be taken to check the pressure within the cabinet and regularly inspect the gloves for perforations and pinholes, to ensure the integrity of the processing area is not compromised. 4
Chapter 6: Work Zones
Chapter 6
Work Zones
Changing of Isolator Gloves This demonstrates the glove changing procedure. This is the sleeve, cuff, the old glove and security ring that holds the glove in place. Please go to: http://www.medskearning.leeds.ac.uk/ pages/aseptics/videos.html to view video number 1 Changing Isolator Gloves.
1. Spray a new pair of gloves into the transfer hatch using local spraying procedures.
4. Push the glove into the sleeve and hold it using the left hand.
7. Thread the new glove through the ring and refit the security ring onto the back groove.
2. Unwrap gloves.
5. Take the new glove and shake it into position, ensuring the thumb is pointing upwards.
8. From inside the new glove, gently ease the old glove off the cuff ring at one point and work it round the diameter of the cuff ring until it is free.
3. Using right hand, remove the left hand security ring using the plastic tab. Manoeuvre the glove from the back groove onto the front groove, carefully ensuring the glove does not slip off.
6. Pull the new glove onto the back groove, holding it in place with the left hand thumb and using the right hand to pull it over the old glove.
9. The glove is now free and can be discarded as contaminated waste. Repeat the process for the other hand.
Chapter 6: Work Zones
5
Aseptic Processing
Contamination There are two types of particulate that can cause contamination in the work zone: viable (living) and non-viable (non-living). Viable contaminants are micro-organisms such as bacteria, viruses and fungi. In general these are carried by people and can be from any of the following sources: l
from dead skin cells;
l
shed from clothing;
l
carried in spital or aerosols from breathing;
l
through direct contact with exposed skin; and
l
through direct contact with a contaminated item.
Non-viable contaminants can be solid particulates such as dust, hair, skin debris that are carried by airborne contamination or chemicals. Chemical contamination can be caused by: accidental spillage, inadequate cleaning, cleaning residues, contact of two containers or cross contamination of products. Static electricity is a small electrostatic charge caused by friction of clothing or very dry air, which can attract dust and debris to surfaces. Information: Static electricity is not a type of contamination, but can encourage contamination by attracting particulates to surfaces.
6
Chapter 6: Work Zones
Action Refer to Chapter 3 Basic Microbiology to refresh your knowledge on micro-organisms and contamination.
Working within LAFC or Isolators Ventilation The primary function of the ventilation system in the work zone is to continually purge the cabinet of particulate contamination. Clean air leaving the HEPA filter should reach the workspace without touching anything else and products should only be exposed to this clean air. Movement Movements within the LAFC or isolator should be very limited and the working area should be kept tidy with the minimal amount of equipment and rubbish within the working space.
Chapter 6
Work Zones
Positioning In the LAFC workstation, the operator should always work downstream of the filter face and should not let hands or arms come between the item which is being protected and the filter.
The importance of air flow and positioning to prevent contamination
Turbulence Turbulence can be caused by rapid movement close to the cabinet. You should take care not to cause turbulence as this can cause contamination by redeposition (moving potential contaminants and redepositing them).
Laminar flow-streamlining-the ideal position. This diagram shows how the air flow should behave in an ideal situation. The air passes around the object and there is no disruption of air flow when the object is positioned correctly in the cabinet.
Cone of turbulence
Most traditional laminar flow cabinets; This diagram shows how turbulence is created by an object as the air moves around it. Your positioning of items within the laminar flow cabinet is very important – well within the cabinet and not too close. You should always make slow and deliberate movements to minimise turbulence.
Dropped Items If an item falls to the floor, you should leave it there until the room has a general clean up at the end of the session, unless it would be dangerous to leave the object on the floor.
Chapter 6: Work Zones
7
Aseptic Processing
Remember l
Hold needles and syringes mid air.
l
Carefully place waste in the cabinet, or eject according to procedures.
l
Vent vials slowly and carefully to prevent aerosols or droplets.
l
Place large bags sideways on to the airflow.
l
Don’t reach across the critical zone when your arms are positioned in the air flow.
l
When handling large containers: l
Hang bottles and bags wherever possible.
l
Position so that the bungs are in the sterile air stream.
l
Position so that the bungs are not close to the surface and are above the turbulent zone.
At the end of each session you should clean down the cabinet following local SOPs and remove any non-essential items.
Test Yourself In your own words explain: Horizontal laminar flow
Vertical laminar flow
8
Chapter 6: Work Zones
Chapter 6
Work Zones
Test Yourself Write down some of things you can remember about working within LAFCs and Isolators
Questions
Q1
What type of airflow is used in the cabinets where you work?
(2)
Chapter 6: Work Zones
9
Aseptic Processing
Q2
Give two specific examples of each of the following types of contaminants.
Viable contaminants: 1.
2.
Non-viable contaminants: 1.
2.
Chemical contaminants: 1.
2.
10
Chapter 6: Work Zones
Chapter 6
Work Zones
Q3
List 4 steps you can take to minimise turbulence while you work.
1.
2.
3.
4.
Q4
Give three reasons for using a transfer hatch on an isolator
1.
2.
3.
Chapter 6: Work Zones
11
Aseptic Processing
12
Chapter 6: Work Zones
