Many low temperature sterilization techniques utilize an ethylene oxide/CFC mixture. The best applications of these types of sterilizing agents are for heat sensitive equipment on which steam autoclaving (sterilization with heat) can not be performed. However, due to the ozone depleting nature of CFCs, alternatives have been developed to eliminate these compounds: 1) 100% Ethylene Oxide Sterilizers, 2) Plasma Sterilization, 3) Chlorine Dioxide Gas, and 4) Ozone Sterilization.

The most effective of the four alternate technologies is the 100% ethylene oxide (EtO) sterilizer. EtO can be applied to many types of medical equipment, and is effective at eliminating all microbial organisms. It is relatively inexpensive and costs less than operating an EtO/CFC mixture. However, EtO is a potent carcinogen that may cause cancer and reproductive failure if personnel are exposed in large quantities. In order to prevent exposure, EtO must be aerated and monitored cautiously while in use. In addition, the lack of CFC tends to make the 100% EtO sterilizer less stable, which may lead to higher explosivity and flammability of the EtO.

The second alternate technology is plasma sterilization. In this process, a gas (e.g. hydrogen peroxide, peracetic acid) is ionized into its plasma phase. The free radicals of the plasma disrupt all cellular activities within the microorganisms, thereby destroying them. This system, though non-toxic and environmentally sound, cannot be applied to many types of medical equipment. Due to the plasma’s corrosive nature, paper, cellulose, and linen cannot be sterilized. It can not be applied to long-channel or lumen devices due to the low penetrating ability of the plasma.

The third alternative is the use of chlorine dioxide gas (ClO₂). In this procedure, a processor converts a compound of dilute chlorine gas with sodium chlorite to form ClO₂ gas. This gas is then exposed to the equipment in a sterilizing chamber. This system operates best in temperatures ranging from 25-30^oC, while utilizing low concentrations of ClO₂. However, this alternative may corrode some materials and must be generated on-site. Prehumidification of the ClO₂ is also required.

The final alternative to CFC sterilization is the use of molecular ozone. In this system, oxygen is converted to gaseous ozone with the use of an electrical current. The ozone gas must then undergo a 70 to 90% humidification phase. The resultant gas is then vented into a sterilization chamber where the microbes are eliminated through oxidation. After this process is complete, the ozone is converted back to oxygen. This system is both non-toxic and environmentally sound. The disadvantages are limited penetrability, possible degradation of some plastics and possible corrosion of metals. This alternative is still in research and development and is not available at this time.

• 100% Ethylene Oxide:
  • Relatively inexpensive;
  • Operation costs lower than EtO/CFC mixture; and
  • Same sterilization techniques as EtO/CFC.

• Plasma Sterilization:
  • Non-toxic and environmentally sound;
  • No aeration required;
  • Requires small power supply for operation; and
  • System is easy to learn.

• Ozone Sterilization:
  • Non-toxic and environmentally sound.

• 100% Ethylene Oxide:
  • Potent carcinogen;
  • Absence of CFC causes an increase in explosivity/flammability;
  • Detector must be installed near sterilizer;
  • Small sterilizer volume chamber; and
  • Existing sterilizers must be replaced.

• Plasma Sterilization:
  • Small sterilizer volume chamber;
  • Expensive;
  • Low penetrating ability;
  • Not effective with paper, cellulose, linen, and angioplasty catheters; and
  • Questionable effectiveness with flexible endoscopes.

• Chlorine Dioxide Sterilization:
  • Exposure effects are undetermined;
  • May corrode some materials; and
  • Low penetrating ability.

• Ozone Sterilization:
  • Low penetrating ability;
  • Will corrode most metals; and
  • Natural gum products and some plastics may degrade.

The ban on CFC production and the phase out of the use of CFCs will force medical facilities to replace existing equipment with ODS free sterilization units. Manufacturers provided the following summaries of some typical costs.

EtO sterilizers range in price between $18,000 - $30,000, depending on the capacity and size of the unit. According to vendors, a 6 cubic foot/169 liter table top unit costs approximately $18,000, and a high capacity 33 cubic foot/679 liter unit costs approximately $30,000. In addition, according to environmental regulations, ethylene oxide detectors must be installed in close proximity to the sterilizer. For more information on these alarm systems please review data sheet 3VII-2 - Ethylene Oxide Sterilizer Alarm Systems.

A plasma sterilization unit costs considerably more than the EtO alternative. Most plasma sterilization units include an automated on-line monitoring system, a non-toxic and non-flammable gas mixture, and a peracetic acid solution. According to vendor information, capital costs for these systems are approximately $120,000. Operation and maintenance costs include replacement gas tanks that cost $630, and the peracetic acid replacements that cost $79.00/case containing four-8oz. bottles.