Inside the Ethylene Oxide Sterilizers Used in Hospitals

When you visit the hospital, you might worry: Are the instruments the doctors use clean? Is there a risk of cross-contamination? In fact, hospitals have a strict disinfection and sterilization system in place. Among these, there is one unassuming yet crucial piece of equipment that quietly safeguards the safety of every patient—the ethylene oxide sterilizer.
Statistics show that it handles over 50% of all low-temperature sterilization tasks in the medical field worldwide. From the flexible tubes used in gastroscopies to dental drills and surgical sutures, its contribution is indispensable behind the scenes. Today, we’ll lift the veil on this “guardian of health.”

Why do hospitals need it? Isn’t high-temperature sterilization more common?

Autoclaving—the high-temperature, high-pressure sterilization method we often hear about—is indeed the most commonly used sterilization method in hospitals. Steam at 121°C can quickly kill all microorganisms. But have you ever considered the following?

1. What if instruments with plastic tubing, such as gastroscopes and colonoscopes, deform or become damaged at high temperatures?
2. What if intraocular lenses used in eye surgery or precision electronic instruments fail when exposed to high temperatures?
3. What if high-molecular-weight materials like disposable masks, syringes, and sutures melt at high temperatures?

This is where the ethylene oxide sterilizer comes in. It can complete sterilization at low temperatures of 50–60°C. It does not damage these delicate, heat-sensitive instruments while achieving the same sterilization efficacy as high-temperature sterilization. The ethylene oxide sterilizers effectively kill all microorganisms, including spores, viruses, and fungi.

How Does It Work? Eliminating Bacteria Through “Chemical Magic”

Core Principle: “Sealing” Microorganisms Through Chemical Reactions
Ethylene oxide (EO) is a gas at low temperatures. Its unique ability lies in alkylation reactions: it can chemically react with the proteins, DNA, and RNA of microorganisms, rendering these vital substances inactive. Whether it’s heat-resistant bacterial spores or stubborn viruses, none can escape.

A complete sterilization process is like giving the instruments a “gas bath”:

1. Pre-treatment: Clean and dry the instruments to be sterilized, then pack them in specialized paper-plastic pouches. Arrange them neatly inside the sterilization chamber, maintaining the appropriate temperature and humidity.
2. Vacuuming: All air is removed from the sterilization chamber to prevent it from hindering the penetration of ethylene oxide gas.
3. Sterilization Phase: Ethylene oxide gas is introduced, maintaining a concentration of 600–800 mg/L. At a temperature of approximately 55°C, sterilization proceeds for 4 hours. This ensures the gas fully penetrates every nook and cranny, reaching even the smallest lumens of the instruments.
4. Degassing Phase: This is the most critical step—repeatedly replace the gas inside the chamber with sterile air. This removes all residual ethylene oxide from the instruments, ensuring the residual level is well below safety standards.
   The entire process takes 12–24 hours. However, it is slower than high-temperature sterilization. It is gentler on the instruments and offers exceptional versatility.

What are its advantages compared to other sterilization methods?

Which items in a hospital undergo this “cleansing” process? It’s more common than you might think.

Application of Ethylene Oxide Sterilizer

1. Central Sterile Supply Department (CSSD): All reusable surgical instruments, endoscopes, and implants from across the hospital are sent here for centralized sterilization; it is the “heart” of the hospital.
2. Department of Dentistry: Instruments that are sensitive to high temperatures—such as dental handpieces, orthodontic instruments, and impression materials—are primarily sterilized here.
3. Ophthalmology: Precision instruments such as intraocular lenses, ophthalmic surgical scissors, and contact lens supplies can only be sterilized using ethylene oxide.
4. Respiratory/Gastroenterology: Flexible endoscopes such as bronchoscopes, gastroscopes, and colonoscopes, as well as various catheters and drainage tubes.
5. Operating Room: Disposable surgical packs, sutures, and high-molecular-weight staplers are sterilized with ethylene oxide during the manufacturing process.

Materials That Can Be Sterilized

✅ Items That Can Be Sterilized

• Plastic and rubber products
• Electronic instruments and optical lenses
• Instruments with long, narrow lumens (endoscopes, catheters)
• Paper and cotton textile packaging materials
• Single-use medical supplies (masks, syringes)

❌ Items that cannot be sterilized

• Food and liquid items
• Oily or powdered items
• Active pharmaceutical ingredients
• Plant-based materials (e.g., traditional Chinese medicinal herbs)

Common Misconceptions About Ethylene Oxide Sterilizers

Misconception 1:

Are ethylene oxide residues carcinogenic, and are medical devices sterilized with it unsafe?

First of all, while ethylene oxide is indeed a carcinogen, the residual level in medical devices sterilized with it must be ≤10 μg/g. This level is lower than the safety threshold for many food additives you consume.
Hospitals conduct a lengthy outgassing process after sterilization to allow residuals to fully evaporate. Each batch is verified for sterilization effectiveness and residual levels using chemical and biological indicators. Only after passing these tests are the instruments put into use, so there is absolutely no cause for concern.

Misconception 2:

Is ethylene oxide flammable and explosive, making its use in hospitals dangerous?

Medical-grade ethylene oxide sterilizers feature multiple safety safeguards:
• The sterilization chamber is completely sealed and equipped with a 24-hour leak detection system that triggers an immediate alarm if concentrations exceed safe limits
• The operating room is equipped with forced ventilation. The concentration of ethylene oxide in the air is strictly controlled below 2 mg/m³, well below the safety threshold.
• All operators have undergone specialized training and are equipped with a full set of protective gear, including gas masks and protective gloves.

Misconception 3:

With today’s advanced technology, shouldn’t ethylene oxide sterilization have been phased out long ago?

Many people view ethylene oxide as “outdated technology.” In reality, it remains the most widely applicable low-temperature sterilization method to this day. For example, when it comes to endoscopes with long lumens or absorbent materials, hydrogen peroxide and plasma sterilization cannot penetrate the interior of the lumens; only ethylene oxide sterilizers can effectively handle these items.
Currently, no other low-temperature sterilization technology can fully replace the role of ethylene oxide sterilization. The World Health Organization continues to recommend ethylene oxide as the preferred method for medical sterilization.

Conclusion

Ethylene oxide sterilizers in hospitals are like unsung “invisible guardians.” You may never have seen them, but they work behind the scenes to ensure the safety of every medical procedure.
The next time you go to the hospital for a checkup or surgery, you’ll realize that behind every sterile instrument you use lies a rigorous sterilization process—and that this equipment is there to safeguard your health.