NEWSLETTER
ISSUE
Oct to Dec, 2022 Volume 20
BRAIN WAVE
VALIDATION of STEAM STERILIZER using STANDARD TEST PACK
Successful validation of sterilizer is one of the most critical steps in attaining effective sterilization of given/desired load. Validation ensures smooth functioning of the sterilizer that meets the desired and intended performance standards of the process. There is an array of qualification tests that can be conducted to validate a sterilizer, such as tests using Chemical Indicators (CI), Biological Indicators (BI), B&D test, etc. Performing these validation tests is necessary to validate that the sterilizer effectively complies with standards such as ISO 17665, PDA Technical report and EN285.
To perform various qualification tests in sterilizer, a Standard Test Pack (STP) is used. Therefore, it is imperative to understand STP in detail.
What is Standard Test Pack (STP)
The test pack comprises of cotton sheets employed to test the steam penetration and temperature of porous loads used in clinical/porous load steam sterilizers. It consists of approximately 7 kg of stacked sheets of a particular cotton weave. Each sheet (120 cm x 90 cm) is folded in half 4 times to form 16 folds.
Why use the Standard Test Pack (STP)
The pack is chosen because it represents the usual maximum density that a clinical sterilizer is designed to process. Under correct conditions, steam will penetrate the whole of the test pack. If the air or other Non-Condensable Gases (NCG) are not removed by the process, a bubble of gas will gravitate to the near centre of pack causing the temperature to decrease. If loads are required to be processed which exceed this maximum, other more additional applicable tests should be performed. The types of load may include for instance, a higher density of fabrics or loads with lumens.
Tests for which Standard Test Pack are used:
- Bowie and Dick test
- Small load thermometric test
- Full load thermometric test (when used in conjunction with other materials)
- Air detector tests (small load, full load and function)
- Small load dryness test (textiles)
- Full load dryness test (textiles)
Let us understand each test in detail.
BOWIE AND DICK (B&D) TEST
The Bowie and Dick Tape test was performed using huckaback linen. It is used to show even and rapid penetration of steam inside the centre of the pack.
Following images from HTM10: 1980 (Health Technical Memorandum sterilizers):
SMALL LOAD THERMOMETRIC TEST
The small load thermometric test is performed to show that the sterilizing conditions for temperature and time have been satisfied. Usually, 7 thermometric test probes are placed inside, on the top of the test pack and at the chamber reference point (normally the chamber drain). The test pack is supported between 100 mm and 200 mm above the nominal geometric centre of the horizontal plane of the usable chamber space. With thermometric logging equipment, the physical parameters are recorded throughout a sterilizing cycle, particularly the temperature.
FULL LOAD THERMOMETRIC TEST TEXTILES (WHEN USED IN CONJUNCTION WITH OTHER MATERIALS)
The full load thermometric test is performed to show that the sterilizing conditions for temperature and time have been satisfied. Usually, 7 thermometric test probes are placed inside, on the top of the test pack and chamber reference point (normally the chamber drain). The test pack is supported as described by the sterilizer manufacturer’s instructions. If this is absent, the pack is placed approximately 100 mm above the nominal geometric centre of the horizontal plane of the usable chamber space. The remainder of the usable chamber space is then filled with textiles as described in EN285. With the thermometric logging equipment, the physical parameters are recorded throughout a sterilizing cycle, particularly the temperature.
- Those entrained in the steam supply then carried over
- Those that remain within the sterilizer load due to poor air removal during sterilizer operation
- Those that are drawn into the sterilizer load and chamber due to leaks during vacuum stages
Air detectors are permanently fitted to the chamber drain point pipework and fall into two categories:
- Pressure sensitive device system
- Temperature sensitive device system
Air Detector Function Test
- The test pack is supported between 100 mm and 200 mm above the nominal geometric centre of the horizontal plane of the usable chamber space.
- During a sterilizing cycle, metered air is leaked into the sterilizer chamber.
- The reaction of the sterilizer control is recorded.
A fault must be indicated by the controller and the chamber door(s) must remain locked until authority is given to release the load.
LOAD DRYNESS TEST FOR A SMALL LOAD OF TEXTILES
- The test pack is weighed
- The test pack is supported between 100 mm and 200 mm above the nominal geometric centre of the horizontal plane of the usable chamber space.
- A sterilizing cycle is initiated within 60 seconds of weighing (empty except for furniture and test pack)
- The test pack is removed and weighed within 120 seconds of completion of the cycle.
- To be acceptable the increase in mass should not be greater than 1%
LOAD DRYNESS TEST FOR A FULL LOAD OF TEXTILES
- The test pack is weighed.
- The test pack is supported as described by the sterilizer manufacturer’s instructions. If this is absent, the pack is placed approximately 100 mm above the nominal geometric centre of the horizontal plane of the usable chamber space. The remainder of the usable chamber space is then filled with textiles as described in EN285.
- A sterilizing cycle is initiated within 60 seconds of weighing.
- The test pack is removed and weighed within 120 seconds of completion of the cycle
- To be acceptable the increase in mass should not be greater than 1%
Pharmalab in association with Dekon Solutions, UK offers Standard Test pack products for your sterilizer validation requirements.
For more details contact us at: pharmalab@pharmalab.com, 022 6622 9900.
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