AAMI-TIR15-1997.pdf
Technical Information Report AAMI TIR15:1997 AAMI Association for the Advancement of Medical Instrumentation Ethylene oxide sterilization equipment, process considerations, and pertinent calculations Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- AAMI TIR No.151997 Ethylene Oxide Sterilization Equipment, Process Considerations, and Pertinent Calculations Approved 4 August 1997 Abstract:This AAMI Technical Information Report (TIR) provides additional guidance to ANSI/AAMI/ISO 111351994, Medical devicesValidation and routine control of ethylene oxide sterilization. The topics covered under this TIR are sterilization equipment, considerations for preconditioning, calculations for relative humidity, calculations of ethylene oxide concentration, and flammability. Keywords:ethylene oxide concentration, flammability, preconditioning, relative humidity, sterilization equipment, calculations Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- Published by Association for the Advancement of Medical Instrumentation 1110 N. Glebe Road, Suite 220 Arlington, VA 22201-5762 © 1998 by the Association for the Advancement of Medical Instrumentation All Rights Reserved This publication is subject to copyright claims of AAMI. No part of this publication may be reproduced or distributed in any form, including an electronic retrieval system, without the prior written permission of AAMI. All requests pertaining to this draft should be submitted to AAMI. It is illegal under federal law (17 U.S.C. § 101, et seq.) to make copies of all or any part of this document (whether internally or externally) without the prior written permission of the Association for the Advancement of Medical Instrumentation. Violators risk legal action, including civil and criminal penalties, and damages of $100,000 per offense. For permission regarding the use of all or any part of this document, contact Kurt C. Larrick, Director, Technical Publishing, at AAMI, 1110 N. Glebe Road, Suite 220, Arlington, VA 22201. Phone: (703) 525-4890, Ext. 239; Fax: (703) 525-1067. Printed in the United States of America ISBN 1-57020-102-1 Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- AAMI TECHNICAL INFORMATION REPORT A technical information report (TIR) is a publication of the Association for the Advancement of Medical Instrumentation (AAMI) Standards Board that addresses a particular aspect of medical technology. Although the material presented in a TIR may need further evaluation by experts, there is value in releasing the information because of the immediate need for it by the industry and the professions. A TIR differs markedly from a standard or recommended practice, and readers should understand the differences between these documents. Standards and recommended practices are subject to a formal process of committee approval, public review, and resolution of all comments. This process of consensus is supervised by the AAMI Standards Board and, in the case of American National Standards, the American National Standards Institute. A TIR is not subject to the same formal approval process as a standard. However, a TIR is approved for distribution by a technical committee and the AAMI Standards Board. Another difference is that, although both standards and TIRs are periodically reviewed, a standard must be acted upon either reaffirmed, revised, or withdrawnand the action formally approved usually every 5 years but at least every 10 years. For a TIR, AAMI consults with a technical committee about 5 years after the publication date (and periodically thereafter) for guidance on whether the document is still usefulthat is, to check that the information is relevant or of historical value. If the information is not useful, the TIR is removed from circulation. A TIR may be developed because it is more responsive to underlying safety or performance issues than a standard or recommended practice or because achieving consensus is extremely difficult or unlikely. Unlike a standard, a TIR permits the inclusion of differing viewpoints on technical issues. CAUTION NOTICE: This AAMI Technical Information Report may be revised or withdrawn at any time. Because it addresses a rapidly evolving field or technology, readers are cautioned to ensure that they have also considered information that may be more recent than this document. Comments on this technical information report are invited and should be sent to AAMI Standards Program, 3330 Washington Boulevard, Suite 400, Arlington, VA 22201-4598. Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- CONTENTS Committee representationvi Acknowledgementsviii Introduction1 1 Scope.1 2 Definitions1 3 EO sterilization equipment.2 4 Determination of minimum product temperature prior to preconditioning. 8 5 Calculation of percent relative humidity10 6 Calculation of EO concentration13 7 Calculations for use of flammability curve18 Annex A Bibliography21 Tables 1 List of constants and molecular weights of some common EO/diluent combinations14 2 Gas constants (R) .16 3 Flamability review, partial pressures, and volume percentage 20 Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- vi© 1998 Association for the Advancement of Medical Instrumentation COMMITTEE REPRESENTATION The AAMI Industrial Ethylene Oxide Sterilization Working Group developed this technical information report under the auspices of the AAMI Sterilization Standards Committee. The AAMI Sterilization Standards Committee has the following members: Cochairs:Virginia C. Chamberlain, PhD William E. Young Members:Carl W. Bruch, PhD, Consultant, Hudson, WI Virginia C. Chamberlain, PhD, Hendersonville, NC Neal E. Danielson, Ds Enterprise, Wichita, KS Judith C. Dowler, Medical Devices Bureau, Health Canada, Ottawa, ON Frank B. Engley, Jr., PhD, University of Missouri, Columbia, MO Victoria Hitchins, PhD, U.S. Food and Drug Administration Collette P. Keyser, RN, Colonel, U.S. Army (Retired), Alexandria, VA Robert F. Morrissey, PhD, Johnson b) reaction with EO or other compounds found as contaminants of EO; c) the polymerization or decomposition of EO. 3.3.2 The sterilizer chamber should be accessible for cleaning. Materials of construction for the sterilizer chamber and the cleaning process should be compatible. The cleaning process should be documented in accordance with good housekeeping practices and the manufacturers internal procedures. 3.3.3 Sensors (e.g., pressure, temperature, gas concentration, relative humidity) should be designed for use in an ethylene oxide sterilization process. Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- 4© 1998 Association for the Advancement of Medical Instrumentation 3.3.4 Auditory and/or visual alarms should be incorporated to alert the operators if the process approaches an out-of-specification condition. 3.3.5 The chamber should be designed to prevent inadvertent access to the load prior to cycle completion using mechanical means (interlocks). If a fault occurs during a sterilization cycle, access to the load shall necessitate the use of a special key, code, or tool. 3.3.6 When the chamber is used to condition a load, either statically or dynamically, equipment should adequately control and document the chamber temperature, chamber pressure, and the conditions necessary to achieve the required process conditions. 3.3.7 Since process conditions inside a chamber may approach the dew point of water, condensation on both product and equipment should be evaluated. Condensation, especially at cold spots, will reduce the partial pressure of water vapor in the chamber, causing additional steam to be added in order to maintain a constant pressure during static conditioning. Excess condensation inside the chamber or on product/packaging can result in interference with the process and can contain dissolved ethylene oxide and derivatives. This dissolved EO may later be released when the load is allowed to dry in the aeration or storage areas, possibly creating a hazard to workers. In addition, condensate in the chamber or load may revaporize and drive the chamber headspace humidity level above validated levels. 3.3.8 The equipment design for the heating and humidification of the sterilizer chamber should avoid direct wetting of the load (e.g., the use of manifolding or baffles). Steam traps, separators, and/or coalescing filters should be used to minimize the entrainment of water in the steam entering the chamber. This facilitates proper heating and humidification of the load. Water used for steam generation should be free of contaminants that can impair the sterilization process or harm the sterilizer or sterilization load. NOTESee 21 CFR 173.310 (1997) and 21 CFR 200.11 (1997) for a list of FDA-approved boiler additives. 3.3.9 Equipment should be selected that has adequate controls to deliver and monitor the selected parameters, such as a) pressure control; b) rate (e.g., sterilant injection, evacuation, etc.); c) temperature control; d) time; e) gas concentration (e.g., weight, volume, pressure, and/or direct analysis); f)humidity. 3.3.10 There should be proper equipment to ensure complete volatilization of the sterilant, thus avoiding nonuniformity in temperature and EO concentration. Common practice is to have the gas inlet temperature at or above the chamber temperature. Excessive heating of the inlet gas should be avoided to prevent problems associated with localized high temperatures within the chamber load. 3.3.11 There shall be equipment to quantify the amount of EO used. The methods of determining EO concentration are: chamber gas pressure monitoring, direct EO concentration measurement, and measurement of the weight or volume of sterilant injected. One method is required for routine processing. During validation, one method other than pressure monitoring is required (ANSI/AAMI/ISO 111351994, section 5.5.2.3). 3.3.12 During initial engineering studies, the sensor(s) used to monitor and control the chamber heating may be temporarily mounted in locations to determine the relationship to the chamber temperature profile. Additional monitoring sensors should be used during these thermal profiles to map the distribution of heat in the usable Copyright Association for the Advancement of Medical Instrumentation Provided by IHS under license with AAMI Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/21/2007 02:51:20 MDTNo reproduction or networking permitted without license from IHS -,-,- © 1998 Association for the Advancement of Medical Instrumentation5 chamber volume. In addition to confirming that the chamber control system and ancillary equipment are properly functioning, such thermal studies will provide important information, as detailed below. a) The minimum and maximum chamber temperatures throughout the cycle and their locations within the usable chamber volume will be determined. These locations should be included in the commissioning studies and subsequently translated into positions within the sterilizer for performance qualification studies. b) The degree of temperature control will also be determined. This determination should include not only the extremes of temperature, but also the capability of the system to control a single point (or an average of multiple points) at a given temperature plus or minus some tolerance. A common tolerance is ± 5.4° F (± 3° C) during exposure. If this is achieved, it is more likely that an 18° F (10° C) range can be achieved within the sterilization load during performance qualification studies. If this degree of temperature control cannot be achieved during the engineering studies, opportunities to enhance process control should be considered prior to validation. Some product configurations may yield excessively wide temperature distributions when profiling the chamber with product, even though the empty chamber profiles were acceptable. This can sometimes be resolved by using a different pallet configuration (e.g., chimney, lowered pallet height, etc.). Product temperature ranges beyond 18° F (10° C) should be evaluated to determine the effect, if any, on the efficacy of the sterilization cycle. c) Since relative humidity is a result of water vapor pressure and temperature, it can significantly differ in various parts of the chamber as a result of temperature differences. As suggested in ANSI/AAMI/ISO 11135, annex A.2.2, “The product design should ensure that functionality and safety are not compromised by exposure to the anticipated range of sterilization conditions.” d) The relationship between the position of the controlling temperature sensor(s) and the characteristics of the heat distribution throughout the usable chamber volume are determined. If the data obtained during chamber profiling (with and/or without product) are acceptable, they may become part of the chamber commissioning file, but only if the controlling temperature sensors remain in these original location(s). If these controlling sensors should be moved, either inadvertently or to affect the chamber pe
