Beyond Traditional Sterilization: The Future

Beyond Traditional Sterilization: The Future

Private Offices & Clinics
Newer and faster types of sterilization processes are being developed for the Alternate Site market where traditionally, sterilization quality assurance has been poor. However, due to recent pressure by Health Departments, OSHA and the media, proper infection control procedures have increased significantly. Currently, the most popular sterilization processes with private-offices and clinics are: Steam, Chemical Vapor and Dry Heat.

  1. STEAM - commonly referred to as an "Autoclave" comes in a variety of chamber sizes and is typically a table-top model with three (3) settings: Unwrapped, Wrapped and Liquids. The cycle time recommended by the manufacturer includes the come up time to heat the vessel and then enough time to kill spores, plus 100% additional kill time added for 100% overkill. Thereby, many manufacturers recommend 40 minute cycles @ 250F/121C or 20 minutes @ 270F/132C. The STATIM by SciCan, is a cassette style sterilizer designed specifically for speed, with approximately a six (6) minute Unwrapped complete cycle time. Wrapped cycles take longer; however, this new technology Steam sterilizer is very popular where "just in time" sterilization is needed. According to the manufacturer, dental handpieces, implants, cutting instruments and fibre optics last longer due to the injector system which provides the temperature consistency of pure steam and expels 98% of the air, which cause oxidation in conventional autoclaves. Now available in two (2) chamber sizes, the STATIM Cassette Autoclave is available from authorized distributors worldwide. The KWIKLAVE by Tuttnauer, is also designed for speed; however, is available in a wide variety of chamber sizes. The smallest unit, Model 1730M offers a total cycle time for Unwrapped instruments of 20 minutes from a Cold Start and 15 minutes from a Hot Start. Meanwhile, the Ritter M9 and M11 by Midmark Corp., have been designed with a door that opens automatically. Both units allow the user to load the chamber, set it, and forget it. According to the Mfg., "you never have to worry about being chained to your sterilizer, because the door opens automatically once sterilization is complete to dissipate steam and give you the fastest drying time possible for your instruments". These newer and faster Steam sterilizers, along with traditional autoclaves are recommended to be tested weekly with Bacillus stearothermophilus spores.
  2. CHEMICAL VAPOR - this sterilizer looks and runs a lot like a Steam unit; however, instead of distilled water, it utilizes a proprietary chemical solution (alcohol/formaldehyde). The Harvey ChemiClave by Barnstead/Thermolyne (formerly sold by MDT Corp.), operates at a pre-set cycle of 20 minutes @ 270F/132C. It is a fully automated sterilizer that promises not to dull, rust or corrode instruments compared to autoclaving. In addition, there is no time-consuming drying phase needed and newer units also offer a seven (7) minute FLASH cycle which is limited to a single instrument. A very load-sensitive sterilizer with numerous packaging restrictions, this unit is popular among dentists and is recommended to be tested weekly with Bacillus stearothermophilus spores (paper strip format only).
  3. DRY HEAT - this sterilization process has undergone several advances in recent years; however, traditional convection style ovens are still prevalent. While convection dry heat sterilizers are recommended to be processed at 320F/160C for 1 to 2 hours, new "rapid heat transfer" units have been developed and are being marketed by two companies. The COX unit by Alpha Scientific, operates at 375F with three (3) settings: Cycle 1 - Unwrapped for 6 minutes, Cycle 2 - Handpieces and drills for 8 minutes and Cycle 3 - Packaged instruments for 12 minutes. The GUARDIAN 2000 by Dentronix, also operates at 375F; however, the cycle times are considerably longer ranging from 35 minutes to 52 minutes depending on the load. These newer and faster Dry Heat sterilizers, along with traditional convection oven units are recommended to be tested weekly with Bacillus subtilus spores (paper strip format only).

Hospitals & Industry
Newer and faster types of sterilization processes have been developed for the hospital and industrial markets, due primarily to environmental issues over CFC's (chlorofluorocarbons) associated with 12/88 EO gas mixtures. Concern over the fate of the earths' ozone layer, the US and 24 other countries agreed to end all production of harmful CFC's by the year 2000. In the US, 12/88 mixture production was banned as of January 1, 1996, forcing suppliers to stock up which will eventually be depleted and no longer be available. Consequently, manufacturers have looked for ways to modify existing 12/88 EO gas sterilizers and/or have developed new alternative sterilization processes for heat-sensitive materials.


  1. HCFC - hydrochlorofluorocarbons are much less stable molecules than CFC's but they degrade rapidly and only 2% are able to reach the atmosphere, which is 50 times less than CFC's. HCFC drop-in cylinders are compatible with most existing equipment with only minor modifications. PENNGAS 2 is a popular HCFC/EO mixture from Pennsylvania Engineering Co. as is OXIFUME 2000 and 2002.
  2. 10/90 MIXTURE - EO and carbon dioxide was the only nonexplosive mixture available before 12/88 came along and solved some quality issues regarding separation in the cylinder and dispensing ease. Castle (now part of Getinge) has worked to solve these problems and their MediFume product (manufacturered by Liquid Carbonic) is available but not as a drop in replacement for 12/88. Although this mixture requires the sterilizer vessel to have a much higher vapor pressure rating than any of the HCFC replacements, it has proven efficacy, meets current CFC guidelines and costs less than 100% EO.
  3. 100% EO - allows users to meet the CFC guidelines and is considered a time tested, effective sterilant that can be used on a wide variety of materials. 3M and STERIS Corp. offer small 100% EO gas units both with and without built in aeration cycles. The Joslyn Sterilizer Corp. (now part of STERIS Corp.) has introduced their Joslyn 2038 model with significantly shorter processing times and a chamber almost twice the size of most 100% EO gas units. The patented Detoxification Process eliminates the need for aeration by using suatmospheric low tempeature steam in a pulsing and flushing sequence to extract the EO. This new and faster process, offers high speed cycles where sharp instruments can be sterilized and ready to use in 30-60 minutes, and most scopes in 60-90 minutes depending on the materials of construction.
  4. STERILANT RECOVERY - systems meet current CFC guidelines and are designed to reduce the cost of running the sterilizer as 80% of the EO gas is recovered for reuse. The reprocessing fee for the recovered sterilant is minimal compared to buying new sterilant. Depending on sterilant consumption, Joslyn states that their Emission Control System will pay for itself within 1-4 years. Joslyn (now part of STERIS Corp.) offers two configurations and says both systems are simple, easy to maintain and compatible with current or future HCFC/EO sterilant mixtures.

Each of these EO gas sterilization systems are recommended to be tested daily - per load with Bacillus subtilus spores.


  1. PERACETIC ACID - is highly toxic is its normal state, but when used in a special formulation it can produce rapid sterilization with a high degree of materials compatibility. The STERIS Corp. has developed such a system and markets it mainly for sterilization of rigid and flexible endoscopes. The STERIS process uses a proprietary chemical sterilant concentrate called "STERIS 20" which is sealed in a tamperproof, single-use continer. This special container ensures safe handling and optimal conceentration of fresh sterilant for each cycle without waste. All items being processed must be totally submersed and the system is controlled at a low temperature of approximately 55C. Author, Sue Crow has written about this system in articles and states the the STERIS System is appealing because it is not damaging to instruments as steam and eo; it works in the presence of of some organic material; there is less chance of human error than processing near the site of operation; and it is nontoxic ot the environment - patient - healthcare worker. The STERIS System is recommended to be tested with Bacillus stearothermophilus spore per the Mfg.'s recommendation.
  2. GAS PLASMA - two companies (Abtox, Inc. and J&JMI) have developed and received FDA clearance to market a newer and faster "Gas Plasma" sterilization process. However, the PlazLyte system by Abtox, Inc. has been recalled by the FDA and therefore, only the STERRAD System by Advanced Sterilization Products (Div. of J&JMI) is available now. This proprietary system is a low temperature sterilization process which is generated by the application of rediofrequency energy to vaporized peroxide. The vapor peroxide is then converted into a variety of active species which sterilizes, leaving behind oxygen and vaporized water. Laboratory tests have demonstrated the STERRAD system destroys a broad spectrum of microorganisms and a wide range of medical and surgical instruments have been tested for compatibility, including heat and moisture sensitive items such as fiber optic cords, batteries, rigid and flexible endoscopes. The STERRAD process requires no aeration or outside venting and the entire cycle is about 75 minutes for the Model 100 and approximately 45 minutes for the Model 50. While there are limitations with the STERRAD System, the manufacturer believes that is has the potential to displace EO gas and many uses of Steam in healthcare facilities. The major limitation to the STERRAD process is that it is not designed for use with cellulosic based products like linen and paper because of their obsorption properties. Many non-cellulosic materials (i.e. tyvek pouches, polyprolylene CSR wrap) are currently available, a wide selection of other products are being developed to support this newer and faster type of sterilization. The STERRAD System is recommended to be tested with Bacillus subtilis spores in the USA and with Bacillus stearothermophilus spores outside the USA, per the Mfg.'s recommendation.
  3. OZONE - Cyclopss Medical Systems has developed ozone generating sterilizers that are compact, easy to operate and cost effective in both hospital and industrial settings. Ozone sterilization is considered safe (no toxic chemicals and no harmful emissions) and all that is needed is oxygen, electricity and a small amount of water. An ozone generator inside the sterilizer converts the oxygen into ozone during sterilization and then the ozone is converted back to water after sterilization is complete. The first Cyclopss sterilizer called the Ster-O3"Zone" 100 is currently under review by the FDA (Food & Drug Adminstration) for approval to market. This sterilizer is designed for hospital use and utilizes an adaped surgical instrument container (Genesis style) as the sterilization chamber. Unsers load the container into the sterilizer and attach four quick-connect fittings. A syringe filled with distilled water is set in place and the user presses a button to start the cycle. A secondary containment chamber closes around the instrument container and the sterilization cycle begins. The instruments are preconditioned and then exposed to humidified ozone gas. Following exposure, the ozone gas is purged from the system and is converted back into oxygen. A printed report confirms the sterilization cycle was completed and data is recorded and stored by the systems's internal computer. The Ster-O3"Zone" 800 is a much larger sterilizer designed for use in manufacturing settings or central processing areas of large hospitals. Using the same ozone generating and control technology, this unit provides a larger and more flexible capacity. On November 1, 1999 it was announced that Cyclopss Corporation had licensed their ozone sterilization technology to Consolidated Stills & Sterilizers of Boston, MA.

Sterilization is a dynamic field and these emerging technologies are generating a lot of interest. Ultimately, the selection of a sterilization process is driven by many factors, including: worker and environmental safety, cycle time, compatibility (medical devices and packaging), and device stability. In previous years, Steam sterilization could not be used on many disposable devices; however, this traditional process is on the rise thanks to improvements in instrumentation (tighter process control) and device compatibility. While Steam sterilization is still the most commonly used process in medical facilities today, these newer and faster types of sterilization offer unique solutions. Are these newer and faster types of sterilization process better? Only time and you, the end-user, will tell!

Copyright, 1999 - 2000. SPSmedical Supply Corp.