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The Complete Guide to Low-Temperature Sterilizers (ETO & H₂O₂)

Health & Fitness
Posted on | by pritesh

1. Definition

What is a Low-Temperature Sterilizer (ETO/H₂O₂)?

A low-temperature sterilizer is a medical device used to sterilize heat-sensitive and moisture-sensitive medical instruments that cannot withstand the high temperatures of traditional steam autoclaves (typically 121-134°C). These sterilizers use chemical agents—primarily Ethylene Oxide (ETO) gas or Hydrogen Peroxide (H₂O₂), either as a vapor or plasma—to destroy all forms of microbial life, including bacterial spores, at temperatures typically ranging from 30°C to 60°C. They are the cornerstone of sterile processing for complex surgical tools, endoscopes, and delicate devices made from plastics, polymers, and optics.

How it Works

The principle is based on exposing instruments to a microbicidal chemical agent under controlled conditions of temperature, humidity, and concentration for a sufficient contact time.

  • ETO Sterilizers: The process is a gas diffusion method. A typical cycle involves:
    1. Pre-conditioning: The chamber is heated and humidified to prepare the microbial load and materials.
    2. Sterilization: ETO gas is injected and maintained at a specific concentration, temperature, and pressure for a set exposure time (often 1-6 hours). The gas alkylates proteins and DNA, preventing cellular reproduction.
    3. Aeration/Desorption: Post-cycle, items are held in a dedicated aerator or within the chamber (with air exchanges) to actively remove toxic ETO residuals absorbed by the materials. This phase is critical for safety and can take 8-12 hours or more.
  • H₂O₂ Sterilizers (Vapor/Plasma): These are often faster, “all-in-one” cabinet systems.
    1. Vacuum Phase: Air is removed from the chamber, creating a deep vacuum.
    2. Injection & Diffusion: Aqueous hydrogen peroxide is vaporized and injected, diffusing evenly around the items.
    3. Plasma Phase (in Plasma Models): An electromagnetic field is applied, creating a low-temperature plasma. The combined action of H₂O₂ vapor and plasma (ionized particles) rapidly destroys microorganisms through oxidation.
    4. Ventilation: The chamber is vented, breaking down the remaining H₂O₂ into harmless water vapor and oxygen. No lengthy aeration is required.

Key Components

  • Sterilization Chamber: A sealed, pressure-rated compartment where items are placed.
  • Control System (PLC/Computer): The brain of the device, controlling cycle parameters, monitoring sensors, and providing user interface.
  • Chemical Delivery System: For safely vaporizing and injecting the sterilant (ETO cartridge/canister or H₂O₂ cassette).
  • Vacuum Pump: Creates the vacuum necessary for air removal and sterilant penetration, especially in H₂O₂ systems.
  • Heating & Humidification System: Maintains precise temperature and humidity levels critical for process efficacy.
  • Aeration System (ETO-specific): Dedicated fans, heaters, and exhaust scrubbers to remove gas residuals.
  • Exhaust/Filtration System: Safely neutralizes and vents used sterilant, often through catalytic converters (ETO) or filters.
  • Sensors & Monitors: For pressure, temperature, humidity, and sterilant concentration to validate each cycle.

2. Uses

Clinical Applications

These sterilizers are essential for reprocessing critical and semi-critical items that are heat-labile:

  • Flexible and rigid endoscopes (gastroscopes, colonoscopes, bronchoscopes, arthroscopes).
  • Complex robotic surgical instruments (e.g., da Vinci instrument arms).
  • Fiber-optic cables, light guides, and cameras.
  • Devices with long, narrow lumens.
  • Electrosurgical pencils, precision motors, and drills.
  • Polymers, plastics, and elastomers used in respiratory, anesthesia, and surgical sets.

Who Uses It

  • Sterile Processing Department (SPD) or Central Sterile Services Department (CSSD) Technicians: Primary operators.
  • Operating Room (OR) Nurses/Technicians: May operate smaller, point-of-use units.
  • Biomedical Engineers/Technicians: Responsible for maintenance and calibration.
  • Infection Prevention and Control (IPC) Teams: Oversee protocol compliance and efficacy.

Departments/Settings

  • Hospital Sterile Processing Departments (SPD/CSSD).
  • Operating Room Suites, especially for “flash” or immediate-use sterilization (using specific, faster cycles under strict guidelines).
  • Ambulatory Surgery Centers (ASCs).
  • Dental clinics (especially for implantology).
  • Ophthalmology and LASIK centers.
  • Veterinary hospitals and specialized clinics.
  • Biotechnology and pharmaceutical research labs.

3. Technical Specs

Typical Specifications

  • Temperature Range: 30°C – 60°C (86°F – 140°F).
  • Cycle Time: Varies widely.
    • ETO: 12 – 18+ hours (including aeration).
    • H₂O₂ Vapor/Plasma: 28 – 75 minutes (total, no aeration).
  • Chamber Volume: Ranges from small tabletop (~25L) to large floor-standing models (500L+).
  • Sterilant Consumption: Measured per cycle (e.g., H₂O₂ cassettes of 50-59% concentration; ETO single-use cartridges or bulk tanks).

Variants & Sizes

  1. Cabinet-style H₂O₂ Plasma/Vapor Sterilizers: Compact, all-in-one, common in OR settings.
  2. Chamber-based ETO Sterilizers with Separate Aerator: Larger, two-unit systems for high-volume processing.
  3. Tabletop vs. Freestanding: Based on footprint and capacity needs.

Materials & Features

  • Chamber Construction: 316L stainless steel, corrosion-resistant.
  • Advanced Features: Built-in biological and chemical indicators readers, RFID tracking of loads, touchscreen interfaces with cycle traceability, remote monitoring, eco-modes, and specialized cycles for lumened devices.

Notable Models/Series

  • Advanced Sterilization Products (ASP): STERRAD NX, STERRAD 100NX (H₂O₂ Plasma)
  • 3M: 8XL, 12XL (ETO)
  • Getinge: GEE E-Series (ETO)
  • STERIS: V-PRO Low-Temperature Sterilizers (H₂O₂)
  • Matachana: LTS ETO Sterilizers
  • Tuttnauer: ETO Series
  • Belimed: a nova (H₂O₂ Plasma)

4. Benefits & Risks

Advantages

  • Material Compatibility: Safe for a vast array of heat-sensitive materials.
  • Excellent Penetration: Can sterilize packaged items and devices with long, narrow lumens (ETO is particularly effective here).
  • High Efficacy: Proven, reliable sterilization when cycles are correctly executed.
  • Speed (H₂O₂): Fast turnaround time compared to ETO.

Limitations

  • Cycle Time (ETO): Very long overall process time, impacting instrument inventory.
  • Toxicity & Residues (ETO): Requires extensive aeration and stringent environmental/worker safety controls.
  • Material Restrictions (H₂O₂): Cannot process cellulose (e.g., linens, paper), liquids, powders, or devices with long, narrow blind-end lumens that restrict vapor diffusion. Some absorptive materials (e.g., endocavity probes) may require specific models/adapters.
  • Cost: High capital and consumable (sterilant) costs.

Safety Concerns & Warnings

  • ETO is a Carcinogen & Mutagen: Requires strict occupational exposure monitoring, proper ventilation, and engineered controls (closed systems, aerators).
  • Explosive Risk (ETO): Pure ETO is flammable; it is often mixed with non-flammable gases like CO2.
  • Chemical Burns (H₂O₂): Concentrated H₂O₂ is corrosive. Cassettes must be handled with care.
  • Inadequate Aeration: Can lead to patient injuries (chemical burns, tissue irritation) from residual ETO on devices.
  • Improper Loading: Can cause cycle failures and non-sterile items.

Contraindications

  • Do not use for items that can be safely sterilized by steam (cheaper, faster, no toxic residuals).
  • Do not process items incompatible with the specific sterilant (always check device Manufacturer’s Instructions for Use – MIFU).
  • Do not use a damaged sterilizer or one with failed indicators.

5. Regulation

FDA Class

  • Class II (Moderate to High Risk): Regulated under FDA 21 CFR 880.6860 (“Sterilizer”). Requires a 510(k) premarket notification to demonstrate substantial equivalence to a predicate device.

EU MDR Class

  • Class IIb: Under EU MDR 2017/745, as devices that control or monitor a vital physiological process and whose failure would pose a significant risk. Requires involvement of a Notified Body for conformity assessment.

CDSCO Category

  • Category C (Moderate Risk): As per the Medical Device Rules, 2017 in India.

PMDA Notes

  • In Japan, regulated as Class II Specified Controlled Medical Devices under the Pharmaceuticals and Medical Devices Act (PMD Act). Requires certification from a Registered Certification Body.

ISO/IEC Standards

  • ISO 14937: Sterilization of health care products – General requirements for characterization of a sterilizing agent and the development, validation, and routine control of a sterilization process.
  • ISO 11135: Sterilization of health-care products – Ethylene oxide – Requirements for development, validation, and routine control.
  • ISO 11140 (Series): Chemical indicators.
  • ISO 17665/ISO 13060: Standards relevant to steam sterilization and small steam sterilizers, often referenced for comparative controls.
  • IEC 61010-1: Safety requirements for electrical equipment for measurement, control, and laboratory use.

6. Maintenance

Cleaning & Sterilization

  • Exterior: Clean daily with a mild detergent and soft cloth. Avoid harsh abrasives.
  • Chamber: Clean weekly or as per MIFU to remove residues. Use recommended neutralizers for chemical spills.
  • Door Seals/Gaskets: Clean and inspect regularly for damage.

Reprocessing

  • The sterilizer itself is not “reprocessed.” It undergoes preventive and corrective maintenance. The focus is on ensuring the load (instruments) is meticulously cleaned and dried before sterilization, as soil or moisture can cause cycle failure.

Calibration

  • Critical sensors (temperature, pressure, vacuum, humidity) must be calibrated annually or as per manufacturer’s schedule by qualified biomedical personnel using traceable standards.

Storage

  • Store in a controlled environment per manufacturer specifications (temperature, humidity).
  • For idle machines, run an empty cycle periodically as recommended.
  • Store sterilant (cassettes/cartridges) in a cool, dry place, away from direct sunlight and according to safety data sheet (SDS) requirements.

7. Procurement Guide

How to Select the Device

  1. Instrument Inventory Analysis: What materials and device types (lumens, length, complexity) do you need to process?
  2. Throughput Needs: How many loads per day? This determines chamber size and cycle time requirements.
  3. Facility & Infrastructure: Do you have space, electrical, ventilation, and plumbing (for vacuum pump) for the system? ETO requires significant exhaust and safety systems.
  4. Lifecycle Cost: Consider capital cost, cost per cycle (sterilant, water, electricity), and maintenance contract costs.
  5. Safety & Ergonomics: Consider staff safety, ease of loading, and user interface.

Quality Factors

  • Validation Data: Robust cycle development and validation for your specific device types.
  • Construction Quality: Durability of chamber, pumps, and seals.
  • Reliability & Uptime: Manufacturer’s track record for mean time between failures (MTBF).
  • Service Network: Availability and quality of local technical support.

Certifications

  • Look for CE Marking (under EU MDR), FDA 510(k) Clearance, and compliance with relevant ISO standards. Local market approvals (e.g., CDSCO, PMDA, NMPA for China) are also essential.

Compatibility

  • Verify compatibility with your tracking software (if used).
  • Ensure biological and chemical indicators used for monitoring are validated for the specific sterilizer model and cycle.

Typical Pricing Range

  • Tabletop H₂O₂ Plasma Sterilizers: $25,000 – $45,000 USD.
  • Large-Capacity H₂O₂ Plasma/Vapor Systems: $45,000 – $80,000+ USD.
  • ETO Sterilizer with Aerator: $80,000 – $150,000+ USD.
  • Note: Pricing varies dramatically based on features, capacity, and region. Consumable costs are an ongoing operational expense.

8. Top 10 Manufacturers (Worldwide)

  1. Advanced Sterilization Products (ASP), part of Johnson & Johnson (USA): Global leader in H₂O₂ plasma sterilization (STERRAD series).
  2. STERIS plc (USA/Ireland): Major player with a comprehensive portfolio, including V-PRO H₂O₂ systems and services.
  3. Getinge AB (Sweden): Offers a wide range of ETO sterilizers (GEE series) and washer-disinfectors.
  4. 3M Company (USA): Historically strong in ETO sterilization technology and monitoring solutions.
  5. Matachana Group (Spain): Renowned manufacturer of ETO and hydrogen peroxide gas plasma sterilizers.
  6. Belimed AG (Switzerland), part of Metall Zug Group: Offers the “a nova” low-temperature plasma sterilizer and full instrument reprocessing lines.
  7. Tuttnauer (Israel/USA): Manufactures both ETO and H₂O₂ plasma sterilizers, known for value and reliability.
  8. Shinva Medical Instrument Co., Ltd. (China): Leading Chinese manufacturer offering a full range, including ETO and H₂O₂ plasma sterilizers.
  9. Sakura Seiki Co., Ltd. (Japan): Japanese leader in sterilizer technology, including low-temperature options.
  10. Andersen Sterilizers (USA): Specializes in ethylene oxide sterilizers, particularly for challenging applications in healthcare and industry.

9. Top 10 Exporting Countries (Latest Year – Based on HS Code 841920)

(Note: This code broadly covers “Sterilizers”; low-temperature is a subset. Data is illustrative of the market.)

  1. Germany: High-value exports of premium sterilization equipment from companies like MMM Group.
  2. United States: Home to major players like ASP, STERIS, and 3M, leading in innovation and high-tech exports.
  3. China: Major and growing exporter of cost-competitive sterilizers (e.g., Shinva).
  4. Italy: Strong in medical device manufacturing, exporting sterilizers and components.
  5. Sweden: Significant exports driven by Getinge.
  6. Switzerland: Exports from Belimed and other precision engineering firms.
  7. Japan: Technology-driven exports from Sakura Seiki and others.
  8. Netherlands: A key European trade hub for medical devices.
  9. France: Home to several specialized medical equipment manufacturers.
  10. United Kingdom: Exports of specialized sterilization equipment.

10. Market Trends

Current Global Trends

  • Shift from ETO to H₂O₂: Driven by safety concerns, regulatory pressure, and the need for faster turnaround, the market is shifting towards hydrogen peroxide-based technologies, though ETO remains vital for specific materials.
  • Point-of-Use Sterilization: Growing adoption of smaller, faster tabletop sterilizers in ORs and ASCs to improve workflow and reduce instrument sets.
  • Integration & Connectivity: Sterilizers are becoming nodes in the “Smart Hospital,” integrating with instrument tracking and facility management systems for complete traceability.

New Technologies

  • Vaporized Hydrogen Peroxide (without plasma): Gaining ground for its material compatibility and slightly lower cost.
  • Ozone-Based Sterilization: Emerging as an alternative, using oxygen and electricity to generate the sterilant on-site.
  • Advanced Monitoring: Real-time cycle parametric monitoring and data logging for enhanced compliance.

Demand Drivers

  • Rising Minimally Invasive Surgeries: Increasing use of complex, heat-sensitive endoscopes and robotic instruments.
  • Growing Ambulatory Surgery Centers (ASCs): Require efficient, compact sterilization solutions.
  • Stringent Infection Control Protocols: Mandating reliable low-temperature options.
  • Aging Global Population: Driving higher surgical volumes.

Future Insights

  • Further automation in sterile processing departments, potentially linking robotic washers directly to sterilizers.
  • Continued development of “greener” sterilants with shorter aeration times and lower environmental impact.
  • Consolidation among major manufacturers and increased competition from Asian manufacturers.

11. Training

Required Competency

Operators must be formally trained and certified, understanding:

  • Microbiology of sterilization.
  • Device-specific operation and loading patterns.
  • Interpretation of physical monitors, chemical indicators, and biological indicators.
  • Emergency procedures and safety protocols.

Common User Errors

  1. Improper Loading: Overloading, blocking fans/sensors, or using non-validated containers/trays.
  2. Inadequate Cleaning/Drying of Instruments: Soil or moisture leads to cycle aborts.
  3. Ignoring or Misinterpreting Indicators: Assuming sterility without verifying all monitors.
  4. Bypassing Safety Protocols: Opening the door mid-cycle, not using personal protective equipment (PPE).
  5. Mixing Incompatible Items: Processing materials (e.g., paper, linens) not validated for the cycle.

Best-Practice Tips

  • Always follow the MIFU for both the sterilizer and the instruments being processed.
  • Use only approved packaging and containers.
  • Perform and document biological monitoring at least weekly, preferably every load.
  • Implement a load quarantine policy until biological indicator results are negative.
  • Establish a comprehensive preventive maintenance program.

12. FAQs

1. What’s the main difference between ETO and H₂O₂ sterilizers?
ETO uses a toxic gas with a very long cycle (including aeration) but has superior penetration for complex devices. H₂O₂ uses a vapor/plasma with a much shorter, aeration-free cycle but has more material restrictions (can’t do powders, liquids, cellulose, some long lumens).

2. Can I sterilize regular surgical stainless steel instruments in a low-temp sterilizer?
Yes, you can, but it’s not efficient. These instruments are designed for steam sterilization, which is faster, cheaper, and leaves no chemical residuals. Use low-temp only for items that cannot withstand steam.

3. How often should biological indicators (BIs) be used?
The gold standard is every load. At a minimum, they must be used weekly and with every load containing an implantable device (which must be quarantined until the BI result is negative).

4. Why does my H₂O₂ plasma cycle keep getting canceled or aborting?
The most common reasons are: 1) Wet instruments (improper drying), 2) Overloaded chamber, 3) Incompatible materials in the load (e.g., paper, linens), 4) Damaged or expired H₂O₂ cassette.

5. Is it safe to be in the room while the sterilizer is running?
For modern, self-contained, closed-system sterilizers, yes, it is generally safe as long as the room is well-ventilated. Always follow the manufacturer’s safety instructions. ETO aerators should be in well-ventilated or dedicated spaces.

6. How long can a sterilized package sit on the shelf?
The shelf life depends on the packaging material, storage conditions (temperature, humidity, cleanliness), and hospital policy. It is event-related, not time-related. A package is considered sterile until it is compromised (e.g., torn, wet, dropped). Many facilities set a conservative time-based policy (e.g., 30-90 days) as a practical measure.

7. Do I need special packaging for low-temperature sterilization?
Yes. You must use packaging validated and approved for the specific type of sterilization process (ETO or H₂O₂). Using the wrong packaging can prevent sterilant penetration or aeration.

8. What should I do if a biological indicator test comes back positive?

  1. Immediately take the sterilizer out of service.
  2. Recall and reprocess all items from the failed load and any loads processed since the last negative BI.
  3. Investigate the cause (operator error, maintenance issue, sterilant problem) with biomedical engineering and infection prevention.
  4. Do not return the sterilizer to service until it has passed a full requalification with three consecutive negative BIs.

13. Conclusion

Low-temperature sterilizers (ETO and H₂O₂) are indispensable, high-stakes devices in modern healthcare, enabling the safe reuse of the most sophisticated and delicate medical instruments. The choice between ETO and H₂O₂ technology involves a critical balance of material compatibility, turnaround time, safety, and cost. Successful implementation hinges not just on purchasing a quality device, but on a holistic system encompassing rigorous staff training, strict adherence to Manufacturer’s Instructions for Use (MIFU), robust maintenance, and unwavering commitment to safety and quality control protocols. As surgical technology advances, so too will low-temperature sterilization methods, continuing to play a vital role in protecting patients from healthcare-associated infections.

14. References

  • Centers for Disease Control and Prevention (CDC). Guideline for Disinfection and Sterilization in Healthcare Facilities (2008).
  • Food and Drug Administration (FDA). Code of Federal Regulations Title 21, Sec. 880.6860 Sterilizer.
  • International Organization for Standardization (ISO). ISO 11135:2014 – Sterilization of health-care products – Ethylene oxide.
  • International Organization for Standardization (ISO). ISO 14937:2009 – Sterilization of health care products.
  • Association for the Advancement of Medical Instrumentation (AAMI). Comprehensive guide to steam sterilization and sterility assurance in health care facilities (ST79). (While focused on steam, principles of sterile processing are foundational).
  • World Health Organization (WHO). Decontamination and Reprocessing of Medical Devices for Health-care Facilities.
  • Manufacturers’ Instructions for Use (MIFU) from leading sterilizer companies (ASP, STERIS, Getinge, etc.).
  • Grand View Research. Medical Sterilization Equipment Market Size, Share & Trends Analysis Report. (For market trend data).