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Our Technology

The exclusive technology behind our success

The Andersen EO-Flexible Chamber Technology (EO-FCT) sterilization process is a unique method of gas sterilization. Compared to traditional EO chambers, EO-FCT systems are considered by FDA to be a non-traditional or “Category B” method of sterilization.

In addition to their remarkable gas efficiency, Andersen EO-FCT systems sterilize at low temperatures without deep vacuum or steam (no external vacuum lines or steam generator) – making our cycles both incredibly compatible and gentle. Learn more about the process and how it compares to older EO technologies below.

eo of Yesteryear

Hospital Sterilization

Skip to: Contract Sterilization

Ethylene oxide was extensively tested by US government labs in the 1930s and 1940s and it was recognized as a promising sterilizing agent. In the 1950s, the widespread introduction of plastics to medical devices required a low temperature method of sterilization compatible with these new materials. EO systems were developed for hospital use, and by the 1960s, EO had become the dominant low temperature sterilization method in US healthcare facilities.

These early hospital EO sterilizers were a breakthrough in low temperature sterilization, but they were not without problems.

  • Large tanks of gas: Early hospital EO systems were typically fed by large external 50lb tanks.  These systems used pounds of EO per cycle, and supplies of additional large tanks required storage in specially ventilated rooms.
  • Wasted Space:  Besides the storage room for EO tanks, these early systems required external air compressors and fixed water lines. EO sterilizers of this era were built into wall units with a service room behind the sterilizers. The EO sterilizers themselves were installed in separate rooms to prevent EO from entering the general workspace (see illustration). This extra room meant hospitals had to dedicate a large amount of space to the installation and operation of their EO sterilizers.
  • Environmental Concerns: Ethylene oxide is flammable and explosive in concentrations above 3%. Manufacturers of these tank systems reduced the potential danger by mixing EO with inert gases. The mixes, however, introduced their own problems – they were far less efficient and (unlike 100% EO) the inert gasses used were discovered to be greenhouse gasses. These EO mixture systems were scheduled for phase-out in the early 1990’s, and were finally taken off the market in 2012.
50lb tank of EO
ST41 ANSI AAMI EO Containment Room, the old hospital ethylene oxide gas sterilization process

NOTE: As explained in the How EO-FCT Works section, our “chamber within a chamber” EO-FCT system performs the same function as installation in a dedicated room as recommended by some industry guidance – making our cabinets a convenient and space-efficient option in any setting.

While EO is an extremely effective steriliant with the widest range of material compatibility, the early traditional EO chamber systems had some significant drawbacks. In the mid-1990s Hospitals began to move away from EO and toward other options such as H2O2 and PPA. We discuss how EO compares to H2O2 and PPA here.

Contract Sterilization

Traditional contract EO sterilization facilities sterilize medical devices by the pallet load. Many current EO “pallet chambers” have the ability to sterilize over fifty pallets of product at once. EO pallet chambers are the typical method for sterilizing most new medical devices, especially products that are produced in large quantities.

Traditional Contract Sterilization Chamber, the old contract ethylene oxide gas sterilization process

However, these large EO contract facilities may not be the best option for manufactures of specialty devices that are produced in smaller volumes. Likewise, firms that are developing new devices and require fast turn around of small numbers of devices require a different solution.

Gas usage is also an issue. A typical EO contract sterilization facility uses between 6 – 8 lbs of EO to sterilize a single pallet of devices. In contrast, our Andersen contract option with a modified EO-FCT system uses just .9 – 1.6 lbs to process the same volume of product. That’s 77-87% reduction of EO consumption.

All of this seems so much more relevant when we speak in terms of the bottom line. With Andersen (in-house or contract) you are able to reduce turn around time, better manage your inventory and maintain control over your product. Contact us to discuss if Andersen contract sterilization or in-house processing is right for you.

Please also see the Environmental Impact tab.

how EO-FCT works

Ethylene Oxide – Flexible Chamber Technology (EO-FCT) is Andersen’s secret sauce. It is exclusive, patented and exhaustively tested. We have several FDA Clearances on the process. Keep in mind if another company is trying to sell you something that sounds similar, it has not undergone this rigorous testing. Our process is precise, reliable and proven.

EO-FCT components, used in the Andersen gas sterilization process

Here’s how it works:

  • Operator readies a load inside the sterilization liner bag with appropriate accessories, gathers the top of the bag around the purge probe bobbin, secures it with the velcro strap, attaches the purge probe quick connect and turns on the machine.
  • The purge probe pulls out all excess air.
  • Operator activates ampoule/cartridge to release EO inside the liner bag, closes the door and starts the cycle.    EO works through to the center of the load. 
  • Anprolene AN74, EOGas 3: EO slowly permeates through the outer liner bag and into the cabinet where it is actively pulled to the outside.
  • Anprolene AN75, EOGas 4: The EO is held in the liner bag through the entire exposure cycle and then pulled out through the purge probe and exhausted to the outdoors during the aeration process.
  • Every two minutes air is pumped into the bag and pulled back out, much like a lung, throughout aeration. Active aeration continues until an operator removes the load, even after the selected aeration cycle ends.

So that’s how EO-FCT works, in a nutshell. A rather apt metaphor. Like a nut, Andersen’s EO-FCT is so effective because it acts as a “chamber within a chamber.” 

Hospital Sterilization Revolutionized by EO-FCT

To look at it from a classic hospital EO sterilization angle (see EO of Yesteryear tab), the sterilization liner bag acts as the EO containment room while the cabinet acts as the operator room. The function of the containment room was to protect operators from incidental exposure – by, ah-hem, containing EO to the one room that was rarely accessed. Our sterilization liner bag is like the containment room. Our cabinet is like the operator room – it is an extra level of protection between the operator and EO. More than just extra “space,” though, the cabinet uses negative pressure to always keep air moving from the front to the back and then to the outside – much like a ventilation hood.

ST41 ANSI AAMI EO Containment Room comparison, Andersen's gas sterilization process takes up less than a forth of the room...even with our largest unit.

Contract Sterilization Revolutionized by EO-FCT

Or to look at it from a classic contract sterilization angle, our sterilization liner bag performs the same function as their huge rigid sterilization chamber. Classic contract sterilization doesn’t have the equivalent of the exterior chamber because excess EO is burned off or simply exhausted into the environment. We’re almost reluctant to point out how badly this has gone in recent years. In one memorable case a simple mistake burning off excess EO blew off a chamber door and threw it across the warehouse and nearly through a wall. Luckily no one was injured. Some residents near contract sterilization plants have had their lives deeply impacted by reports of elevated EO emissions – especially in Illinois and Georgia.

Traditional Contract Sterilization Chamber compared to an Andersen Sterilizer, gas sterilization process compared

There just isn’t a comparison…

Our EO-FCT is so unlike both of these classic methods. Comparing our sterilizers to one of them is like saying, “You know, I’m anti-car because ’57 Chevys are just not safe. They don’t have airbags, no ABS, for God’s sake they don’t even have seat belts. Also, the ’57 Chevy, it’s dirty. It doesn’t have catalytic converters. It’s polluting to the environment and it only gets 10 miles to the gallon. I don’t like cars. It’s a bad technology.” 

If someone came to you and tried to make that argument, you would politely point out that no one is making the ‘57 Chevy for exactly those reasons. You’d point the conversation toward modern hybrid technology that get 50 miles to the gallon and modern crash test technology.

Train vs. Prius

Or another fun comparison: What about a coal-driven train engine versus a modern hybrid car? They are both modes of transportation and could get you to the same place (maybe) but, really, there’s just no comparison.


Terminal Sterility

Achieves FDA-required 10-6 sterility assurance level (SAL) for terminal sterilization of medical devices.


Terminal sterility (10-6 SAL) with 90% less EO than any other system on the market. EOGas 3 sterilizers use even less per cycle.

Smart Cabinet Design

A ventilation port in the back of the cabinet actively draws fresh air from the room through the cabinet and out the back exhaust through the entire cycle. Ensuring air flow in one direction and significantly mitigating risks.


Achieve 10-6 SAL without those those damaging downsides: high heat, steam, deep vacuum, oxidation or corrosion. Our process is damage-free.


EO has the unique ability to penetrate many packaging materials, leaving your devices sterile and protected from contamination. We even have several FDA-clearances for that.


We have models from tabletop to refrigerator-sized. Most designs fit conveniently on a countertop or table.

Easy Installation

Easiest in the industry; requires only a dedicated electrical outlet and an exhaust line. See your sterilizer’s specific specs for full details.

Zero Emissions

Andersen’s optional emissions abator is a simple, cartridge-based system that employs a dry catalyst resin. The resin converts ethylene oxide to biodegradable organic compounds. Replaceable cartridges are non-hazardous.

high Capacity

Our sterilizers generally hold a 35L liner bag. Customers report they can often fit 5x what they can put in an average autoclave. If you need more capacity than that, we have the EOGas 3 Series that hold multiple bags and can run 6-10 cycles independently. 

Unmatched compatibility

Sterilizes your most delicate instruments, electronics, drills, fiber optics, hand pieces and cameras. As well as those plastic, fabric, cellulose or rubber items that you can’t sterilize with other methods. Most any item with the exception of food, drugs or liquids can be sterilized.

Active Aeration

Andersen’s purge probe flushes the liner bag with a constant flow of fresh air at the end of the cycle – no need to transfer items to a separate area. Active aeration continues indefinitely until products are removed.

Okay, these don’t have to do with our technology – but they’re still important benefits!


All of our lines are priced very economically – both in terms of cost to purchase and per cycle.

Many practices see return on investment in a few months or even a few weeks.

Easy to Use

Customers report this as their favorite feature all the time. You just set it and forget it.

The easy user interfaces and aeration in the same chamber, make the process a snap!

Free training

We are always happy to train your sterilizer operators – for the entire useful life of your sterilizer. 

We’ll train just one person or your whole staff – over the phone, virtually or sometimes even in person.

Environmental Impact

Environmental impact

Because we don’t sterilize “dead space” (see EO of Yesteryear tab), we can use a micro-dose of EO – The precise amount necessary to sterilize your items. This means our sterilizers use far less gas. As a consequence of using less, we are also naturally emitting far less.

We also offer optional emission abators. The simple, cartridge-based system employs a dry catalyst resin that converts ethylene oxide to biodegradable organic compounds. Replacement cartridges remove more than 99% of the EO in the exhaust stream, resulting in a fraction of a gram of total EO emissions over the course of a multi-hour cycle. This tiny amount of EO is vented to the outside where it disperses rapidly, quickly becoming undetectable. Effectively making the process zero emission.

While traditional contract sterilization facilities can emit 1 or more tons of EO every year, even our worst case calculation (running 24 hours a day, 365 a year, without stopping even for aeration), our systems emit 24 – 96.5 lbs of EO per year. With an abator those numbers become .24 – .97 lbs.

Two National-Level Regulatory Environmental Awards

Innovation is in our DNA. Recognized by the Food and Drug Administration (FDA) as an EO thought leader, Andersen was selected as one of eight international companies to collaborate on the development of strategies or technologies to reduce EO emissions to as close to zero as possible in its FDA Innovation Challenge. Challenge collaboration is on-going. 

In addition, Andersen was recognized with the 2020 Small Business Environmental Stewardship Award for its high-efficiency, low-emission sterilization process and its cooperation with State and Federal officials on regulatory and permitting issues.

2019 FDA Innovation Challenge 2 Winner
High Efficiency EO Sterilization Process

2020 SBA Environmental Stewardship Award
Zero Emission Technology