EO Residual Testing Solutions
STERIS offers biocompatibility laboratory testing services to the medical device manufacturing industry for residues from EO processing
Any medical device that is sterilized by ethylene oxide (EO) and comes in contact with a patient must undergo residual testing to analyze the EO residual levels. The residues can be harmful to the end user or patient. It is important to patient safety that all devices meet the limits set forth in the ISO 10993-7 standard.
The limits will vary depending upon the intended use of the device as there are three main categories a device may fall under: limited use, prolonged use and permanent use. In addition, there are several special device categories that have their own unique set of limits. Devices that do not have patient contact are not required to meet this standard.
Devices considered as surface-contacting or implantable must meet an additional set of criteria called the tolerable contact limit (TCL). The purpose of this limit is to prevent localized irritation due to the release of ethylene oxide (EO) or ethylene chlorohydrin (ECH) from the device. The TCL is a calculated value that takes into consideration the surface area of a device and the residual levels in order to determine if irritation will be an issue.
Residue testing is performed during sterilization validation studies to determine:
- Required ambient or heated aeration specifications
- EO reprocessing (2X) and applicable aeration for process risk mitigation
Root causes to high residual levels?
- There are several reasons why a device may contain high levels of residues after being exposed to the ethylene oxide sterilization process:
Material: certain materials will absorb and retain gas molecules more than others. Natural materials such as cellulose and cotton are known to be very absorbent. Some types of plastics are also known to show high absorption rates when exposed to EO processing.
- Packaging: EO processing requires breathable packaging such as Tyvek or medical grade paper to allow the gas molecule to pass through. Packaging with a minimal or obstructed breathable surface area (i.e., large adhesive label) will not allow gas to move as freely across the breathable barrier.
- Load configuration: the volume, density and overall configuration of the load on a pallet can impact the ability of gas removal after processing.
Residual Testing is used for:
- Medical Devices