Sterilization with EtO is a low-temperature process (typically between 37 and 63°C) that uses Ethylene Oxide gas to reduce the level of infectious agents. EtO is used in gas form and is usually mixed with other substances, such as CO2 or steam. It is mainly used for products that cannot withstand the heat of typical autoclave sterilization such as plastic. The main physical parameters to be monitored are temperature and relative humidity.
The total length of the process can vary depending on the goods that are being sterilized, but typical cycles are between 36 and 48 hours. There are two main ways to divide the cycle; a three phase cycle and a five phase cycle. The difference being that a three phase cycle does factor in the pre and post exposure phases.
A typical three phase EtO sterilization cycle can be summarized as follows:
Provides temperature and humidity conditions to entice infectious agents to come out of hibernation
Sterilization / Conditioning:
Exposure to the sterilizing agent at the specified temperature, RH% and pressure levels
Et0 gas is removed using changes of air in the sterilization chamber removing any EtO particles. This process is usually taking place in a separate chamber or room. Time and temperature are monitored.
Given the hazards associated with the handling of Ethylene Oxide, the EtO sterilization process requires Intrinsic Safe Material Zoning (ATEX). Ellab offers a fully compliant and safe solution for this application because the majority of the Ellab data loggers are ATEX certified (see certificates). No matter the specifics of application, Ellab has a flexible solution to cover any individual needs.
Ellab manufactures high-accuracy relative humidity, pressure and temperature sensors, which are specially designed to withstand the hazardous environment associated with the use of Ethylene Oxide. They maintain the highest accuracy available on the market. The use of a combined relative humidity and temperature sensor decreases the need for extra equipment and allows for easier data caollection.
The TrackSense® Pro data loggers are capable of recording up to 120,000 sample points with a programmable acquisition time to suit your process. This ensures that you will have the capability of recording the complete length of your process without concerns of data storage.
For real-time data collection during EtO processes, the use of cables is no longer required. Ellab’s SKY system allows for wireless radio transition of data directly to your PC for documentation and process control. Given the modularity characteristics of all Ellab equipment, you can observe the points that are critical for monitoring in real-time and afterwards consolidate all data into one report.
EtO sterilization cycles are run in chambers which are sealed to prevent the leak of EtO gases into the atmosphere. The use of thermocouples or wired monitoring systems present great difficulties in handling and positioning the sensing elements.
The TrackSense® Pro data logger’s small size allows them to be placed easily within the product load. When using Ellab's wireless data logger system you will avoid any leak possibility of chamber.
The effectiveness of the EtO sterilization cycle depends on the level of relative humidity and temperature in the cycle, thus it is important to monitor and validate these parameters through the process. Ellab’s combined temperature and relative humidity sensors provide an all-in-one solution. The robustness of Ellab sensors allows you to validate a complete cycle, even with the presence of EtO, which will significantly reduce setup time.
The TrackSense® Pro logger for EtO sterilization is made of stainless steel and its electronics are hermetically sealed, which protects the equipment from chemical exposure. The majority of Ellab equipment has an ATEX certification that accredits it as intrinsically safe.
The requirements and recommendations for EtO sterilization validation vary from country to country. The ISO standard 11135, “Validation and routine control of ethylene oxide sterilization,” provides astandard that is commonly accepted and used worldwide as the reference for the control of EtO sterilization. This standard offers a guideline about the information that needs to be documented for each phase of the cycle, and provides the minimum number of temperature and relative humidity measuring points depending on the size of the chamber.
When validating an EtO sterilization process, it is necessary to perform a mapping of the chamber and monitor temperature and relative humidity to evaluate the performance of EtO sterilization. Both empty and loaded chamber tests are required.
It is recommended that the acceptance criteria for the performance of the EtO sterilization is formulated from a worst-case scenario perspective.
Depending on the size of the chamber, ISO standard 11135 provides a recommendation on the number of temperature and relative humidity sensors required for validation. The location of the sensors must provide a useful representation of the behavior of the chamber throughout the cycle. The creation of a thermal map with an empty chamber provides the location of the most critical points to monitor during the process (ex. cold spot).
Creating and documenting sensor positioning is an important part of the documentation for the process control. Using the Unit tool inside the ValSuite™ Pro software, it is possible to have a documented map of sensor placement that will facilitate repeatable and comparable studies.
Once the position of the sensors in the chamber has been documented, it is necessary to observe the sensor position on the product. ValSuite™ software facilitates the documentation of sensor placement in the cold spot by allowing users to include descriptions and pictures for all of the channels used.
If real time data feed is needed, the TrackSense® Pro equipment can be expanded with the SKY option so the information collected can be viewed in real-time from your PC.
Once all data is collected, the user must observe the characteristics of the process. When analyzing temperature, it is usually required that the variation in load temperature measurements must be not greater than 2°C. The variation in the wall temperature must be not greater than 5°C.
In terms of relative humidity, the difference between the sensors must be not more than 20%, when working in a range of 40 to 85%.
The ValSuite™ Pro Software provides tools to analyze the performance of the vessel in all phases of the process. The use of time-markers help to generate graphical and analytical reference points in the data collected. Statistics calculations such as min, max and delta as well as evaluation of the calculated statistics is also available in the software. The limit report offers a quick evaluation of the process which informs the user if the established criteria has been met (ex. sensors maintain a specified temperature range).
ValSuite™ Pro software integrates all calculations into self-generated reports without the need to export data into other software. Reports can also include the placement of the loggers inside the vessel and descriptive pictures of sensor positioning. Please see the example of the PDF document. Generating ValSuite™ reports provides the highest data security for the results due to the FDA 21 CFR Part 11 compliance.