Enbio autoclave - tests you can make: what are they and what is their use?
The autoclave is a device for extremely important, but also difficult special tasks. It must guarantee the user full security, which results from its efficiency and fulfillment of its tasks. How to check if our autoclave is working as it should? What tests to perform?
An autoclave is a device in which the steam sterilization process is carried out. It is a kind of thermal, high-temperature sterilization. Its goal is to completely kill all microorganisms on tools, including their spore forms. The result of properly conducted sterilization is a fully sterile product. It is considered sterile if the chance of survival of the microorganisms becomes less than one in a million.
Autoclave - why is its efficiency so important?
The autoclave sterilizes with high pressure steam, which is the sterilizing agent. Water vapor has a higher biocidal activity than dry hot air. It is one of the best methods of destroying all forms of microorganisms found on reusable tools, incl. surgical instruments, laboratory instruments, as well as nippers, files, tattoo machines, etc. It can be said that an autoclave is a hermetically sealed container that can be heated. Due to the special structure, it is possible to maintain high pressure and high temperature in the device. This process can be divided into four stages - emptying, leveling, sterilization and cooling. In the first stage, the autoclave is deaerated and the atmospheric air is replaced with water vapor under negative pressure. Air is removed from the chamber alternately and replaced with steam. Then, the temperature is evened out and the sterilization process takes up to 15 minutes at 121 degrees Celsius. The last phase is cooling. The pressure in the chamber is lowered and a vacuum is created. Its purpose, apart from lowering the temperature, is to remove steam from the sterilizer chamber, dry sterilized instruments and prevent steam condensation, which may cause corrosion of the tools.
The autoclave is used not only in hospitals, laboratories and other medical facilities, but also in beauty salons, dentists' offices, tattoo parlors, and wherever the skin is broken or may be broken and, as a consequence, infection with microorganisms that are harmful to health. That is why it is so important to monitor the sterilization processes - the autoclave must be a guarantee of safety. The sterility of the tool cannot be seen with the naked eye and cannot be directly assessed. However, we know the parameters that we must obtain to confirm the effectiveness of sterilization. You should therefore carry out regular process checks and document them with the many tests available on the market.
Classification of chemical tests
In accordance with the European standard EN IS0 11140-1: 2014, we distinguish 6 categories of tests that control the course of autoclave sterilization:
Type 1, category e1
These are chemical process indicators which only indicate that the sterilization process has been carried out. Most often they are in the form of tapes placed on the outer surface of the package or, for example, indicators printed on paper and foil packages. They do not inform about whether the sterilization process was carried out correctly, they will only show an error if there is a very large irregularity.
Type 2, Category S2
Type 2 chemical indicators control specific test procedures. They show whether the steam penetrates quickly and evenly and the air is removed during the sterilization process. It is i.a. the Bowie-Dick test or the Helix test used. These tests must meet the requirements set out in the PN-EN ISO 11140 standard. They are carried out on a hot autoclave, preferably at the same times.
Type 3, category i3
These are indicators of one variable in the sterilization process (single-parameter), reacting, for example, only to too low temperature. Currently rarely used.
Type 4, Category i4
The tests of this category are multi-parameter indicators that respond to two or more critical variables. Compared to Category 1 and Category 3 tests, they provide more information. The manufacturer specifies the parameters by which the benchmarks reach their endpoint. However, they do not inform about the exposure time or the permeability of the sterilizing agent.
Type 5, category i5
This category includes integrated indicators that show whether all the necessary critical values have been achieved during sterilization. Thanks to these tests, we can be sure that the sterilization process was 100% effective.
Type 6, category i6
These are emulation indicators that react to absolutely all critical variables in the final stage of sterilization, ensuring the highest control and safety of sterilization. These are the most stringent tests for packet and batch control. Different numbers of indicators are used depending on the size of the autoclave, for example, in autoclaves up to 12 liters, two indicators are used. They have a tighter tolerance than Category 5 tests.
What tests can be carried out in an autoclave?
Vacuum test is a leak test. For autoclaving to be effective, the steam must be in close contact with the equipment being sterilized. That is why it is so important to check that any air that can restrict water vapor penetration and act as an insulation barrier has been completely removed. These tests show possible failures, e.g. pumps or door seals and check the tightness of the valves. According to European standard EN 13060, leakage can be 1.3 mbar / min or less within 10 minutes.
The Helix test is a steam penetration test inside a Class B (medical grade) autoclave of highly recessed loads. It is effective in sterilization, especially with respect to hollow and porous instruments, into which water vapor can penetrate with difficulty. A 150 cm long tube with a diameter of 2 mm is used for this. At one of its ends there is a chemical test, the color of which changes upon contact with water vapor.
Bowie & Dick Test
The Bowie-Dick test is a vapor permeability test for porous materials. It is in the form of a sheet of paper that changes color when exposed to a certain pressure of saturated vapor. If the test sheet turns a uniform color without stains of different colors, this indicates thorough water vapor penetration. If the vacuum is not properly formed, there is a leak while creating it, or if poor quality steam is produced - the test will fail.
How to test in an Enbio autoclave?
The vacuum test should be performed daily to ensure proper sterilization. The vacuum test takes about 20-30 minutes, depending on the device. In the ENBIO S / PRO autoclave, the check in the test program takes 16 minutes. The device should be cool, dry and empty for inspection. If the test is negative, repeat the procedure. After two unsuccessful attempts, you need to contact the service.
The Helix test should be performed daily prior to instrument sterilization. It is dedicated to control the sterilization of long, porous and / or hollow-shaped instruments. It must be carried out in an empty autoclave, in accordance with the requirements of EN 13060, in a preheated chamber, on the lowest tray at the steam outlet or according to the manufacturer's instructions. If all physical sterilization conditions are as required, the marker will turn a uniform color. If it does not, then the sterilization was not successful and another test should be performed. If the test fails a second time, repair or replacement of the autoclave is required.
Bowie and Dick test
The Bowie & Dick test should also be carried out daily, after long periods of inactivity and after each service of the autoclave. In accordance with European standards EN 13060, it should be performed in an empty chamber, using the test mode dedicated to this type of test (at 134 degrees C, within 3.5 minutes). It should also be placed in the center of the lowest tray in the autoclave. After the test, the color of the sheet should be checked - it should change evenly, with the same intensity, from the center to the edge. If the first test is negative, repeat it, two abnormal tests oblige the autoclave service.
- The International Pharmacopoeia, Methods of sterilization, https://apps.who.int/phint/pdf/b/184.108.40.206.8-Methods-of-sterilization.pdf
- Moshtaq Talip Al-mohanna, Sterilisation and disinfection, https://www.researchgate.net/publication/315804456_STERILISATION_AND_DISINFECTION
- STERIS, Chemical Indicators for Steam Sterilization, https://www.sterislifesciences.com/resources/documents/article-reprints/chemical-indicators-for-steam-sterilization
- Euronda, Vacuum Test - What is it and why is it important?, https://prosystem.euronda.com/vacuum-test-what-is-it-why-important/
- Pharmaceutical microbiology, What is the importance of Vacuum leak Test, http://pharmaceuticalmicrobiologi.blogspot.com/2017/01/what-is-importance-of-vaccum-leak-test.html
- Euronda, Helix tests for autoclaves - What is it and why is it important?, https://prosystem.euronda.com/helix-tests-for-autoclaves-what-is-it-and-why-important/#:~:text=The%20Helix%20Test%20measures%20the,may%20infect%20patients%20and%20operators
- Isopharm, Steam Penetration Test – Mythbusting!, https://training.isopharm.co.uk/blog/steam-penetration-test-mythbusting/
- Euronda, Bowie & Dick test, https://prosystem.euronda.com/bowie-dick-tests-what-is-it-and-why-important/