Sterilization of Health-Care Products — Ethylene Oxide — Requirements for the Development, Validation and Routine Control of a Sterilization Process for Medical Devices
ISO 11135:2014, with Amendment 1:2018 revising Annex E on single-batch release, specifies requirements for developing, validating and routinely controlling an ethylene-oxide (EO) sterilization process for medical devices in both industrial and healthcare-facility settings. It covers process and product definition, microbiological methods including the overkill and other bioburden-based approaches, installation, operational and performance qualification (IQ/OQ/PQ), and control of EO and ethylene-chlorohydrin residuals, which link to ISO 10993-7. A revision, ISO/FDIS 11135, is in progress but not yet published, so the 2014 edition with its 2018 amendment remains current.
What this does not cover
stated in the document's own scope- It does not cover moist-heat sterilization — steam processes follow ISO 17665.
- It does not cover radiation sterilization, addressed by ISO 11137.
- Toxicological limits for EO and ethylene-chlorohydrin residuals are set in ISO 10993-7, not this standard.
- It does not evaluate overall device biocompatibility, which is governed by ISO 10993-1.
Always verify against the current published text before relying on it for a submission or inspection.
Overview
ISO 11135:2014 is the international standard for ethylene-oxide sterilization of medical devices, covering process development, validation and routine control. EO is used for heat- and moisture-sensitive devices that cannot withstand steam, so the standard balances microbial lethality against toxic-residual control. It defines how to characterise the process and product, choose a microbiological approach, qualify the equipment, and demonstrate that each routine load achieves sterility. Amendment 1:2018 revised Annex E, which addresses release of a single production batch. A further revision (ISO/FDIS 11135) is under development but not yet published, so the 2014 edition plus its 2018 amendment is the current requirement.
Legal basis & how it acquires force
ISO 11135 is a voluntary consensus standard that gains force through regulatory recognition and contractual reference rather than statute. FDA lists it as a recognised consensus standard for EO-sterility evidence in device premarket submissions, and it carries harmonised-standard weight for conformity with the EU Medical Device Regulation (EU) 2017/745. Inside a device quality system it is invoked through ISO 13485 process-validation requirements, and its residual-control provisions connect to the biological-safety obligations of ISO 10993.
Document structure
| Part | Covers |
|---|---|
| Scope and terms | EO sterilization of medical devices; ties to ISO 11139 vocabulary. |
| Process and product definition | Bioburden, sterilizing-agent parameters and load configuration. |
| Validation | IQ, OQ and microbiological/physical PQ, including overkill and bioburden methods. |
| Routine monitoring and control | Physical parameters, biological indicators and load release. |
| Residual control | EO and ethylene-chlorohydrin limits and aeration, linked to ISO 10993-7. |
| Annex E (as amended 2018) | Single-batch release considerations. |
Key requirements
- Define the EO process and product, including preconditioning, humidity, gas concentration, temperature, dwell time and aeration.
- Establish the microbiological approach — overkill (half-cycle) or a bioburden-based method — and the target sterility assurance level.
- Qualify the sterilizer and any preconditioning and aeration areas through IQ and OQ across the specified operating range.
- Demonstrate lethality through performance qualification using biological indicators and physical parameter measurement.
- Control ethylene-oxide and ethylene-chlorohydrin residuals within limits, referencing ISO 10993-7.
- Monitor each routine cycle against defined physical parameters and release each load against predetermined criteria.
- Maintain the validated state through requalification, calibration and change control.
Implementation tips
- Anchor the half-cycle overkill rationale to measured product bioburden so the sterility-assurance argument is reproducible.
- Treat aeration as part of the process, not an afterthought, and tie residual limits to ISO 10993-7 endpoints for the specific device contact category.
- When adopting Amendment 1:2018, update single-batch release procedures against the revised Annex E rather than the original 2014 text.
International alignment
Developed by ISO/TC 198, ISO 11135 is the ethylene-oxide member of the healthcare-sterilization family beside ISO 17665 (moist heat) and ISO 11137 (radiation), all under the ISO 11139 vocabulary. FDA recognises it for EO-sterility evidence, and it is a harmonised standard under the EU MDR. Its residual requirements align with ISO 10993-7, and Amendment 1:2018 harmonised the single-batch-release annex.
ISO 11135:2014: frequently asked questions
Quick answers to common questions about ISO 11135:2014.
What does Amendment 1:2018 change in ISO 11135:2014?
It revised Annex E, which addresses the release of a single production batch, refining the parametric-style release approach.
Does ISO 11135 apply to healthcare facilities as well as manufacturers?
Yes. It covers EO sterilization processes in both industrial and healthcare-facility settings.
What is the overkill approach?
A half-cycle method that demonstrates a large lethality margin against biological indicators, establishing a validated process without extensive bioburden characterisation.
Is ISO 11135:2014 still current?
Yes. A revision (ISO/FDIS 11135) is in progress but not yet published, so the 2014 edition with Amendment 1:2018 remains in force.