Hydrogen peroxide gas plasma sterilizers

The only reason that one would want to monitor H2O2 in an SPD (Sterile Processing Department) would be if a hydrogen peroxide gas plasma sterilizer were installed.  The OSHA PEL for hydrogen peroxide is 1 ppm,  Full PubChem record.

At present, there are two manufacturers of such sterilizers: Advanced Sterilization Products, Division of Ethicon Inc., a Johnson & Johnson company; and Steris. The former is known as a STERRAD®, and the latter is sold as the V-PRO®.

Because it was introduced several years earlier than the V-PRO®, there is much more field history on the STERRAD®.

While some have cast doubts on the efficacy of the STERRAD® process to sterilize various medical devices, the units have compiled an admirable safety record, with no known cases of harm to users caused by vapor-phase hydrogen peroxide. Still, H2O2, especially in the concentrated solution needed for the STERRAD® is a dangerous compound, being a strong oxidizer, capable of inflicting severe burns on personnel, as well as causing explosions under certain conditions.

Indeed, STERRAD posts a Safety Data Sheet (SDS) for the hydrogen peroxide cassettes on its website, as they must, since the chemical is used in its process. Some conclude, by comparing the NIOSH IDLH (Immediately Dangerous to Life or Health) levels, that hydrogen peroxide (75 ppm) is more dangerous than EtO (800 ppm).

Advanced Sterilization Products has advised interested customers as follows:

The STERRAD® Sterilization Systems utilize a variety of safety features, such as a mechanical door locking mechanism, to reduce occupational exposure to hydrogen peroxide. The STERRAD® Sterilization Systems deliver hydrogen peroxide into the sterilization chamber and the hydrogen peroxide is vaporized at a reduced pressure (vacuum). Because the chamber pressure never rises above atmospheric pressure during the cycle, the sterilizer retains the hydrogen peroxide safely withing the chamber.

In addition, the plasma stage of the sterilization cycle converts the hydrogen peroxide molecules within the chamber to water vapor and oxygen. During the pump down stage prior to plasma treatment, or at pump down after a cycle has been completed, all vapor removed from the sterilization chamber passes through a filter that is specially designed to decompose hydrogen peroxide into non-hazardous water vapor and oxygen.

Internal validation testing, and independent testing results performed by NATLSCO Risk & Safety Services have shown that the hydrogen peroxide emission is significantly less than the OSHA limit.

It is worth noting this early report on leaks from a STERRAD® sterilizer.  Also of interest is this study from 2012.

Steris has advised interested customers as follows:

Exposure to Liquid Peroxide: Under normal conditions of use, the sterilizer operator is not exposed to the contents of the VAPROX HC Sterilant container (59% hydrogen peroxide). The vented sterilant cartridge is completely sealed, and the user cannot access the sterilant without physically damaging the cartridge. A MSDS is provided with the sterilant to advise the user on safe handling practices.

Exposure to Hydrogen Peroxide Vapors: The user places a sealed, vented sterilant cartridge into the sterilizer. The sterilizer automatically dispenses and injects peroxide into the low pressure chamber. At the end of each sterilization pulse, hydrogen peroxide vapor is removed from the chamber through a catalytic converter which converts the peroxide into water and oxygen. To confirm this, the environment around the sterilizer was monitored for acceptable VHP (vaporized hydrogen peroxide) levels during typical sterilization cycle conditions. The levels were >8 times lower than the OSHA hydrogen peroxide gas Time Weighted Average (TWA) limit of 1 ppm.

There have been persistent reports of various objects in the SPD being bleached out, including the black anodized doors of 3M EtO sterilizers. Many attribute such actions to hydrogen peroxide in the workplace.

Given such reports, as well as the above mentioned leakage studies, and recognizing that hydrogen peroxide does indeed have regulatory limits, continuous monitoring of affected areas in sterile processing departments is highly recommended.

While many SPDs are installing hydrogen peroxide monitoring systems, the reluctance on the part of some facilities seems to be based on promises made and over-the-top sales pitches whereby “evil” ethylene oxide could now be safely replaced with hydrogen peroxide.  Alas, real life is proving to be not quite as simple as that.

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