Chemical apparatus and process disinfecting – deodorizing – preser – With safety feature
Reexamination Certificate
1999-01-29
2002-05-14
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
With safety feature
C422S002000, C422S026000, C422S105000, C422S292000, C324S314000, C324S316000, C324S600000, C049S029000
Reexamination Certificate
active
06387332
ABSTRACT:
DESCRIPTION
This invention relates in general to a safety system, and more particularly to an accurate and reliable safety system for a gas sterilization facility which prevents a person from opening the chambers in the facility if dangerous levels of gas are present in the chambers.
BACKGROUND OF THE INVENTION
Gas sterilization facilities exist throughout the world. These sterilization facilities are used to sterilize a variety of articles such as medical devices, surgical instruments and other healthcare supplies and equipment. The sterilization process used to sterilize these articles must completely kill or destroy the microorganisms on these articles.
Ethylene oxide sterilization is a widely used, effective method for sterilizing such articles. Ethylene oxide gas is an extremely effective bactericide for metal objects, such as surgical implements, as well as relatively delicate instruments and equipment including synthetics or plastics. Moreover, since ethylene oxide gas is effective at relatively cool temperatures, the ethylene oxide sterilization process does not employ high temperatures which can degrade articles made of certain materials. Ethylene oxide gas also penetrates certain packaging materials and is therefore effective in sterilizing articles in appropriately designed packages. Ethylene oxide sterilization is preformed on a large scale at sterilization facilities having multiple industrial size sterilization chambers and on a smaller scale at facilities, such as hospitals, which typically have one or relatively few, smaller sterilization chambers. During the ethylene oxide sterilization process, the packaged articles to be sterilized are placed in a sterilization chamber, the door of the chamber is closed, sealed and locked and a process is initiated including drawing a vacuum and sometimes injecting steam in the chamber. Ethylene oxide gas is then introduced into the sterilization chamber for a period of time sufficient to sterilize the articles in the sterilization chamber.
During the sterilization process, certain amounts of the ethylene oxide gas are physically absorbed into the articles undergoing sterilization. After the articles are exposed to certain levels of ethylene oxide gas for a period of time, the ethylene oxide gas in the sterilization chamber (which is not absorbed into the articles) is exhausted or flushed from the chamber. However, the ethylene oxide gas which was absorbed by the articles is not immediately removed from the sterilization chamber. The ethylene oxide gas absorbed by the articles is slowly “desorbed” from the articles back into the sterilization chamber. As the ethylene oxide gas is desorbed from the articles into the sterilization chamber, the desorbed ethylene oxide gas may be exhausted or flushed from the sterilization chamber. However, since desorption occurs over an extended period of time and is an irregular uncontrolled process, even after the sterilization chamber has been exhausted or flushed multiple times, the atmosphere in the sterilization chamber will most likely still contain ethylene oxide gas desorbed from the articles, subsequent to the last exhausting or flushing cycle for the chamber. Even though the amount of ethylene oxide gas that is in the articles can be measured, it is difficult to know when and at what rate the ethylene oxide gas will be desorbed from articles into the sterilization chamber. The sterilization chamber thereby includes a vent exhaust system which is automatically triggered when the door of the chamber is slightly opened. The vent exhaust system directs the vented gas from the chamber to emission control equipment which may include one or more ignition sources.
Ethylene oxide gas is toxic to human beings, flammable and potentially explosive. If the door of a sterilization chamber is opened when a certain level of ethylene oxide gas is present in the chamber (i) due to incomplete exhausting or flushing of the chamber, (ii) after additional ethylene oxide gas is released into the sterilization chamber due to the continued desorption process, (iii) at the wrong time during the sterilization cycle, or (iv) after there has been an unknown equipment or control malfunction, the gas mixture in the vent exhaust system and chamber could be flammable and have the potential to ignite causing an explosion to occur as a result of the explosive gas mixture coming into contact with any of several potential ignition sources. Also, the person opening the chamber or the other people in the sterilization facility could be exposed to the toxic ethylene oxide gas. This creates a potentially dangerous environment for the personnel operating the sterilization facility, especially since the desorption process is irregular and uncontrolled.
For safety purposes, strict procedures must be followed while opening the door to any sterilization chamber. These procedures include creating sufficient vacuum draw downs of the gas in the chamber, followed by a gas in-bleed of air or nitrogen (i.e., gas washes) which removes much of the ethylene oxide gas from the articles and packaging in the chamber. Thereafter, the door of the chamber is slightly opened, which triggers the back vent or vent exhaust system. The back vent draws air into the chamber through the opening between the door and the door frame, to flush out the empty chamber space surrounding the articles and packaging. After a predetermined period, the chamber door may be fully opened to remove the articles and packaging in the sterilization chamber. These procedures may not be followed due to human error, equipment failure or control system failure. Accordingly, there is a need for accurate and reliable safety systems in gas sterilization facilities, and particularly in ethylene oxide sterilization facilities, to measure the level of ethylene oxide gas in the sterilization chamber and to prevent opening of the door to the sterilization chamber if the level of ethylene oxide in the chamber is above a predetermined level.
Microwave spectrometers are generally known for detecting the presence and concentration of ethylene oxide gas and other gases. For example, U.S. Pat. Nos. 5,209,902, 5,399,314 and 5,548,217 disclose the use of microwave spectrometers for detecting the presence and concentration of ethylene oxide gas. Microwave spectrometers have also been employed to measure the concentration of ethylene oxide gas in a sterilization chamber to facilitate parametric release of the articles. For example, Griffith Micro Science, Inc. currently uses microwave spectrometers to facilitate parametric release on a limited number of ethylene oxide sterilization chambers. The microwave spectrometer used by Griffith Micro Science, Inc. is generally described in the publication entitled
Specificity, Accuracy, And Interpretation Of Measurements Of Ethylene Oxide Gas Concentrations During Sterilization Using A Microwave Spectrometer
published in the Rev. Sci. Instrum. (68) 7, July 1997. No known ethylene oxide sterilization facility, however utilizes a microwave spectrometer in a reliable and accurate safety system which prevents access to the sterilization chambers based on the concentration of ethylene oxide gas in the sterilization chambers.
Accordingly, there is a need for an accurate and reliable safety system or other apparatus or method to determine whether it is safe to unlock the door of a sterilization chamber, and in particular an ethylene oxide sterilization chamber, based on the measured concentration of sterilization gas in the sterilization chamber regardless of whether those levels are due to continuing desorption of the sterilization gas from the articles and packaging into the sterilization chamber, human error or equipment or control system malfunction. The desired safety system must prevent the opening of a sterilization chamber when a dangerous level of sterilization gas is present in the sterilization chamber.
SUMMARY OF THE INVENTION
The present invention solves the above problems by providing an accurate and reliable safety system for a gas steriliz
Dickinson Warren P.
Lange Franklin S.
Legg James S.
Chorbaji Monzer R.
Dorsey & Whitney LLP
Griffith Micro Science, Inc.
Warden, Sr. Robert J.
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