ISO/DIS 11140-3:2025(en)

ISO TC 198/WG 6

Date: 2025-06-03

Sterilization of health care products — Chemical indicators — Part 3: Type 2 indicators for use in the Bowie and Dick-type steam penetration test

Stérilisation des produits de santé — Indicateurs chimiques — Partie 3: Indicateurs de Type 2 pour utilisation lors de l'essai de Bowie et Dick de pénétration de la vapeur

© ISO 2025

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 General 4

5 Requirements 4

6 Indicator format 5

7 Performance requirements 5

8 Packaging and labelling 6

Annex A (normative) Estimation of visual difference between colour of the substrate and of the changed or unchanged indicator system by determination of relative reflectance density 8

Annex B (normative) Determination of uniform colour change on exposure to saturated steam 12

Annex C (normative) Determination of non-uniform colour change on exposure to a reference fault condition 13

Annex D (normative) Reproducibility and determination of the reference fault condition in the standard test pack 15

Annex E (normative) Determination of indicator colour change on exposure to dry heat 19

Annex F (normative) Determination of shelf life of indicators 20

Annex G (normative) Determination of transfer of indicator to standard test pack on processing 21

Annex H (normative) Steam exposure apparatus and steam for test purposes 22

Annex I (normative) Standard test pack 25

Annex J (normative) Air injection system 26

Annex K (informative) Relationship between chemical indicator components 28

Annex ZA (informative) Relationship between this European Standard and the General Safety and Performance Requirements of Regulation (EU) 2017/745 aimed to be covered 29

Bibliography 33

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 198, Sterilization of health care products. This third edition cancels and replaces the second edition (ISO 11140-3:2007), which has been technically revised.

The main changes are as follows:

— change of title from class 2 indicator to type 2 indicator to align with ISO 11140-1;

— correct use of the terms indicator and indicator system to align with ISO 11140-1;

— updated normative references;

— inserted common Clause 4 for ISO/TC 198 documents, replacing Clause 8;

— aligned indicator labelling with ISO 11140-4;

— aligned Annex B with ISO 11140-4;

— modified Annex D to allow same methods of creating reference fault condition as ISO 11140-4;

— moved Annex F to Annex E;

— added Annex L, modified from ISO 11140-1.

A list of all parts in the ISO 11140 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

The Bowie and Dick test ^[1] is a test for steam sterilizers for products to be sterilized that are within sterile barrier systems or other porous loads. As such it is performed during the demonstration of conformance of steam sterilizers to EN 285 and as a routine test in ISO 17665. The test method is described in EN 285.

A failure of the Bowie and Dick test is symptomatic of a number of potential problems with the sterilizer that could compromise the uniform sterilization of a load to be processed. This failure is not conclusive proof that the fault in the sterilizer is due to air retention, air leakage or non-condensable gases, and it can be necessary to investigate other causes of failure.

The Bowie and Dick test was conceived as a test for successful steam penetration into a standardised test load in high-vacuum porous-load sterilizers used in the sterilization of health care products.^[1] A successful Bowie and Dick test indicates sufficient air removal to facilitate rapid and even penetration of steam into the test load. A failure of the Bowie and Dick test is symptomatic of a number of potential problems with the sterilizer that could compromise sterilization of the load. The presence of air within the load may be due to an inefficient air removal stage, an air leak during the air removal stage, or non-condensable gases in the steam supply, are circumstances that can lead to failure of the test. This failure is not conclusive proof that the fault is due to air retention, air leakage or non- condensable gases, and it can be necessary to investigate other causes of failure.

The result of the test can also be affected by other factors which inhibit steam penetration. The test does not necessarily demonstrate either achievement of the required temperature or maintenance of that temperature for the required time to achieve sterilization.

In this document, the Bowie and Dick test consists of two components:

a) a small, standardised test load;

b) a chemical indicator to detect the presence of steam.

The Bowie and Dick test as originally described ^[1] utilized huckaback towels as the material for the test load. The test as described in EN 285 uses cotton sheets for this purpose.

Because a range of different tests in different countries has historically been termed the Bowie and Dick test, the term “Bowie and Dick-type test” is used in this document. Further information is given in ISO 15882.

Sterilization of health care products — Chemical indicators — Part 3: Type 2 indicators for use in the Bowie and Dick-type steam penetration test

WARNING — The use of this document can involve hazardous materials, operations and equipment. It is the responsibility of the user of this document to establish appropriate safety and health practices and determine the applicability of any other restrictions prior to use.

This document specifies the requirements for a Type 2 chemical indicator to be used in the steam penetration test for steam sterilizers for wrapped health care goods (instruments, etc., and porous materials).

Chemical indicators conforming with this document are intended for use in combination with the standard test pack as described in EN 285. This document does not consider the performance of the standard test pack, but does specify the performance of the chemical indicator.

NOTE The Bowie and Dick-type test is used for routine testing of steam sterilizers and validation of steam sterilization processes.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

EN 285:2015+A1:2021, Sterilization — Steam sterilizers — Large sterilizers

ISO 5457:1999/Amd 1:2010, Technical product documentation — Sizes and layout of drawing sheets

ISO 5636‑3:2013, Paper and board — Determination of air permeance (medium range) — Part 3: Bendtsen method

ISO/CIE 11664‑2:2022, Colorimetry — Part 2: CIE standard illuminants

ISO 11140‑1:2014, Sterilization of health care products — Chemical indicators — Part 1: General requirements

IEC 60584‑1:2013, Thermocouples — Part 1: EMF specifications and tolerances

IEC 60751:2022, Industrial platinum resistance thermometers and platinum temperature sensors

For the purposes of this document, the terms and definitions given in ISO 11140-1 and the following apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

chamber reference temperature

temperature at a specified point within the chamber

Note 1 to entry: The specified point is usually located in the chamber drain or active chamber discharge of the steam exposure apparatus.

[SOURCE: ISO 11139:2018/Amd 1:2024, 3.38, modified – Note 1 to entry has been added.]

3.2

chemical indicator

test system that reveals change in one or more pre-specified process variables based on a chemical or physical change resulting from exposure to a process

Note 1 to entry: See Annex K.

[SOURCE: ISO 11139:2018/Amd 1:2024, 3.43, modified – Note 1 to entry has been added.]

3.3

chemical indicator system

combination of a chemical indicator (3.2) and a specific test load

Note 1 to entry: See Annex K.

[SOURCE: ISO 11139:2018, 3.43.1/Amd 1:2024, modified – Note 1 to entry has been added.]

3.4

exposure time

period for which the chamber reference temperature lies within the sterilization temperature band

3.5

reference fault period

period of 30 s commencing when the chamber reference temperature attains the set operating temperature

3.6

sterilization temperature

minimum temperature on which the evaluation of sterilization efficacy is based

Note 1 to entry: This is the minimum temperature of the sterilization temperature band.

Note 2 to entry: The use of the word sterilization within this and other definitions is not intended to imply that sterilizing conditions will take place under the test cycle conditions.

[SOURCE: ISO 11139:2018/Amd 1:2024, 3.286, modified – Note 1 to entry and note 2 to entry have been added.a]

3.7

temperature band

range of temperatures expressed as the minimum and maximum temperatures which prevail during the specified period of a cycle

Note 1 to entry: These temperatures are usually stated in whole units.

[SOURCE: ISO 11139:2018, 3.293/Amd 1:2024, modified – Note 1 to entry has been added.]

3.8

temperature depression

thermodynamic temperature difference in kelvin (Celsius) given by (chamber reference temperature, in Celsius) minus (temperature in the standard test pack, in Celsius)

EXAMPLE 2 K (2 °C).

3.9

test equilibration time

<indicator> time elapsed after the chamber reference temperature attains the set operating temperature until the temperature within the standard test pack is the same as the chamber reference temperature

[SOURCE: ISO 11139:2018/Amd 1:2024, 3.297]

4.1 The development, validation and routine control of a sterilization process is a critical element in product realization of health care product. To ensure the consistent implementation of the requirements specified in this document, the necessary processes need to be established, implemented and maintained. Processes of particular importance in relation to the development, validation and routine control of a sterilization process include but are not limited to:

— control of documentation, including records,

— assignment of management responsibility,

— provision of adequate resources, including competent human resources and infrastructure,

— control of product provided by external parties,

— identification and traceability of product throughout the process, and

— control of non‑conforming product.

NOTE ISO 13485 covers all stages of the lifecycle of medical devices in the context of quality management systems for regulatory purposes. National and/or regional regulatory requirements for the provision of health care product can require the implementation of a full quality management system and the assessment of that system by a recognized conformity assessment body.

4.2 A process shall be specified for the calibration of all equipment, including instrumentation for test purposes, used in meeting the requirements of this document.

5.1 Unless specified otherwise in this document, the requirements of ISO 11140-1 shall apply.

5.2 Test samples shall be conditioned to 23 °C ± 1 °C and 50 ± 2 % RH prior to testing for performance.

5.3 The indicator shall have sufficient strength to withstand steam sterilization and subsequent handling.

5.4 A thermometric recording instrument(s) shall be used in conjunction with temperature sensors to record the temperatures measured in the locations specified in the tests described in this document. The temperature-measuring equipment used in all test methods for demonstrating conformance with this document shall meet the following requirements:

a) Temperature sensors shall be either platinum resistance and conform with Class A of IEC 60751:2022, 5.2.3.1, or a thermocouple and conform with one of the tables of tolerance class 1 of IEC 60584-1:2013, Clause 5.

b) The performance characteristic of the temperature sensor shall not be affected by the environment in which it is used, e.g. pressure, steam or vacuum.

c) The temperature sensors shall have a response time in water of Ʈ₉₀ ≤ 0,5 s.

d) The temperature measured by all temperature sensors when immersed in a temperature source at a temperature known to within ±0,1 K (±0,1 °C), and within the sterilization temperature band, shall not differ by more than 0,5 K (0,5 °C).

e) The recording instrument shall record the temperature from a minimum of 6 sensors. The sampling interval shall not exceed 2,5 s. All data sampled shall be used for the interpretation of results.

f) The scale range shall include 0 °C to 150 °C. For analogue instruments, the minor mark interval shall not exceed 1 K (1 °C), the resolution shall be not less than 0,5 K (0,5 °C) and the chart speed shall be not less than 15 mm/min. Digital instruments shall register and record in increments of not more than 0,1 K (0,1 °C).

g) The limit of error of the recording instrument between 0 °C and 150 °C (excluding temperature sensors) shall not exceed 0,25 % when tested in an ambient temperature of (20 ± 3) °C. The additional error due to change in the environmental temperature shall not exceed 0,04 K/K (0,04 °C/ °C).

h) Calibration shall be carried out using a working or reference standard that is traceable to a national standard or a primary standard. The thermometric recording instrument shall have a valid test certificate.

i) The calibration instrument shall have a valid test certificate.

The format of the chemical indicator shall meet the following requirements.

a) The indicator reagent shall be distributed to cover not less than 30 % of the surface area of the substrate. The distance between adjacent areas of indicator reagent shall not exceed 20 mm.

The pattern of indicator reagent distribution should permit clear interpretation of the colour change at the margin with the colour change in the central region.

b) It shall have an air porosity not less than 1,7 µm/(Pa.s) when tested in accordance with ISO 5636-3:2013, Clause 10 at an air pressure of 1,47 kPa.

c) The indicator substrate shall have a colour which is uniform to visual observation.

d) The indicator shall have a difference in relative reflectance density of not less than 0,3 between the colour of the indicator substrate and either the changed indicator or unchanged indicator as specified [see ISO 11140-1:2014, 5.8 c)].

Conformance shall be tested in accordance with Annex A.

e) It shall permit writing in permanent ink to be made legibly on both processed and unprocessed materials. Markings made before processing shall be legible after processing.

f) It shall be of size A4 in accordance with ISO 5457:1999/Amd 1:2010, 3.1.

7.1 The indicator, when tested in combination with the standard test pack specified in Annex I, shall:

a) show a uniform colour change conforming with 6 d) after exposure to a non-fault operating cycle at an exposure time of 3,5 min at 134 °C, or an exposure time of 15 min at 121 °C, or at any other time/temperature combination specified by the manufacturer when the temperature tolerance shall be and the time tolerance shall be ±5 s.

Conformance shall be tested in accordance with Annex B.

b) show a non-uniform colour change when exposed to the reference fault condition (see Annex D) where a concentration of residual, induced or injected air or non-condensable gases is created in the standard test pack.

Conformance shall be tested in accordance with Annex C.

7.2 The indicator shall show no discernible colour change after exposure to dry heat at (140 ± 2) °C for not less than 30 min.

With some indicators, a slight colour change can occur after exposure to dry heat; this shall be acceptable if the change that occurs is slight or markedly different from that brought about by exposure to steam in accordance with 7.1 a) and within the limits specified in the instructions for use (see ISO 11140-1:2014, 5.8).

Conformance shall be tested in accordance with Annex E.

7.3 The indicator shall not visibly transfer chemical indicator reagent to the material of the test load in intimate contact with the indicator during processing.

Conformance shall be demonstrated in accordance with Annex G.

7.4 The indicator shall conform with the requirements of this document for the duration of the shelf life specified [see ISO 11140-1:2014, 5.8 j)].

If any change in the indicator occurs during ageing, it shall be different from the change on exposure to saturated steam [as described in 7.1 a)] and shall either inactivate the indicator so that no further change can take place or not affect the performance of the indicator according to 7.1 a) and 7.1 b).

Conformance shall be tested in accordance with Annex F.

8.1 Each indicator shall be marked with:

a) the sterilization temperature(s) at which the product is designed to be used (see ISO 11140-1:2014, 5.7);

b) a unique code from which the manufacturing history can be traced [see ISO 11140-1:2014, 5.8 k)];

c) the expiry date under the specified storage conditions [see ISO 11140-1:2014, 5.8 j)];

d) at least the information summarized in Figure 1.

Adjacent to each heading there shall be a clear space not less than 5 mm × 20 mm for the user to enter the required information at the time of use or, if the size of the indicator does not permit this, each indicator shall be supplied with a means of retaining the indicator as a permanent record which shall be printed with the information given in Figure 1. The means of retention shall permit writing in permanent ink to be made in association with the indicator.

NOTE This is an example of a suitable format. Other formats and/or text can be used.

Figure 1 — Provision for recording information to be provided on or with each indicator

8.2 The product shall be packed in such a way as to allow easy separation of individual units of product and to protect the product from moisture, dust, sunlight and damage in normal transit, to the extent necessary to ensure that the indicator retains its performance throughout the stated shelf life when stored in accordance with the instructions for use.

Conformance shall be tested by inspection of the technical documentation.

8.3 The outside of each indicator primary pack shall be marked with the sterilization temperature(s) at which the product is suitable for use.

8.4 The information supplied (see ISO 11140-1:2014, 5.8) shall include sufficient instructions on the use of the indicator system to enable correct interpretation of the test results.

8.5 When requested by the purchaser, a certificate of conformity to the requirements of this document for each lot of product supplied shall be available.

8.6 The information supplied may take the form of internationally recognised symbols. See, for example, ISO 15223-1.

8.7 The product shall be identified with a unique identification or UDI carrier (see ISO 11140-1:2014, 5.8).

1. 
   (normative)
   
   Estimation of visual difference between colour of the substrate and of the changed or unchanged indicator system by determination of relative reflectance density
   1. Principle

The relative reflectance density of the changed indicator and the substrate shall be determined in accordance with the method given in A.3.

NOTE This method is based on ISO 5-1, ISO 5-3 and ISO 5-4.

Relative reflectance density, D_Rf, is calculated as follows:

(A.1)

(A.2)

where

is the reflected flux from the indicator;

is the reflected flux from the substrate;

To completely define a type of density spectrally, it is necessary to specify the light source, optics and spectral response of the measuring system.

• 1. Apparatus

A.2.1 Steam exposure apparatus, as specified in Annex H.

A.2.2 Illuminant D₆₅, with a relative spectral power distribution, as specified in ISO 11664-2:2022, Clause 5.

A.2.3 Photoelectric reflectance photometer, giving within 0,3 % an indicated reading proportional to the intensity of light reflected from the surface under test. The instrument has the following characteristics.

A.2.3.1 Optical geometry

The optical geometry shall include illumination of the specimen at angles between 40° and 50°, viewed along the normal (0°) with an angle of acceptance (observer angle) of 10°.

The dimensions of the measurement aperture of the instrument shall permit the measurement aperture to be entirely filled with substrate or indicator reagent.

To minimize measurement errors, the optical system should be equipped with a polarizing filter if the surface to be measured is highly reflecting, e.g. a plastic-coated surface.

A.2.3.2 Spectral response

For the visual reflectance density, the combined spectral sensitivity of the receiver and spectral characteristics of the components on the efflux section of the measuring instrument shall match the spectral luminance efficiency in photopic vision, designated V_(λ). The product of V_(λ) and the reflection densitometer illuminance E_A, wavelength by wavelength, defines the spectral products required of the measuring instrument in order to provide comparison of visual densities. The spectral product of the measuring instrument shall be within ±20 % of the values given in Table A.1.

NOTE These conditions assume that there is no fluorescence in the optical elements of the instrument or the sample.

A.2.3.3 Calibration

Reflectance density is determined using a perfectly-reflecting and perfectly-diffusing material as a reference standard. Such a material does not exist, but the response that would theoretically be obtained from such a material can be compared with a suitable secondary reference standard, e.g. compressed barium sulfate or enamelled metal plaques which can then be used to calibrate the densitometer.

The measuring instrument shall be calibrated against reference samples previously calibrated by a National Reference Laboratory.

The instrument shall indicate values within ±3 % of the calibrated values of the reference samples.

A.2.3.4 Background

While readings of the reflectance density of the substrate and the indicator are being made, the sample shall be in contact with a backing material which is spectrally non-selective and diffuse-reflecting.

• 1. Test method
     1. Sample conditioning

Samples shall be conditioned to, and in equilibrium with, (23 ± 2) °C and (50 ± 5) % relative humidity when tested.

NOTE Standardized conditions are recommended because some materials change density with variations in temperature and relative humidity.

• • 1. Procedure

Expose the indicator within the standard test pack to a cycle of the steam exposure apparatus at the specified operating temperature for the indicator system, to produce a uniform colour change in the indicator reagent in accordance with 7.1 a).

Determine the relative reflectance density of the indicator reagent on the substrate by using the substrate as the reference reflectance.

Carry out this measurement on three samples for each of three lots of the indicator.

• 1. Test report

The test report shall contain at least the following information:

a) name and address of the indicator manufacturer;

b) batch numbers of the individual batches of indicator tested;

c) make, model and serial number of the test instrument;

d) calibration details traceable to a national standards authority;

e) temperature chart records of the steam exposure to which the indicators were exposed;

f) mean and range of the relative reflectance density measurements;

g) date of test;

h) identification of the test operator.

Table A.1 — Values of spectral product required of the reflectance photometer at the given values of wavelength and illuminance

1. 
   (normative)
   
   Determination of uniform colour change on exposure to saturated steam
   1. Apparatus

B.1.1 Steam exposure apparatus, as specified in Annex H.

B.1.2 Standard test pack, as specified in Annex I.

B.1.3 Temperature sensors and thermometric recording instruments, as specified in the requirements for test instrumentation given in 5.4.

• 1. Procedure

B.2.1 Insert thermocouples in accordance with EN 285 into the standard test pack in accordance with Annex I. Insert the indicator to be tested into the centre of the standard test pack. Expose the indicator combined with the standard test pack to a cycle of the steam exposure apparatus with the holding time and temperature pre-set to those specified in 7.1 a). At the commencement of the plateau period, the difference between the measured temperature in the drain of the steam exposure apparatus and in the centre of the test pack shall be less than 0,5 K (0,5 °C) and shall be so maintained throughout the plateau period in order that the test remain valid.

B.2.2 At the end of the operating cycle, remove the standard test pack from the steam exposure apparatus and remove the indicator. Examine the indicator for conformance with 7.1 a).

B.2.3 Repeat test three times for each of three separate production batches of the indicator.

NOTE The steam exposure apparatus door can cool down between consecutive tests, thus the highest reproducibility is obtained if the time period for the unloading-loading-start sequence is kept short and constant.

1. 
   (normative)
   
   Determination of non-uniform colour change on exposure to a reference fault condition
   1. Apparatus

C.1.1 Steam exposure apparatus, as specified in Annex H, fitted with an air injection system as specified in Annex J.

C.1.2 Standard test pack, as specified in Annex I.

C.1.3 Steam supply, as specified in EN 285.

C.1.4 Thermometric recording instrument, meeting the requirements of 5.4 to record the temperature from a minimum of six temperature sensors. The temperature sensors shall be introduced into the chamber through the temperature-sensor entry connection and fitting.

• 1. Procedure

C.2.1 Insert thermocouples into the standard test pack in accordance with EN 285. Insert the indicator to be tested into the centre of the standard test pack. Expose the indicator combined with the standard test pack to a cycle of the steam exposure apparatus with the holding time and temperature pre-set to those specified in 7.1.

C.2.2 If used (see C.2.5), locate the nozzle of the air injection system (25 ± 5) mm above, and perpendicular to, the geometric centre of the upper surface of the test pack

C.2.3 Expose the assembled standard test pack to a cycle of the steam exposure apparatus. The operating temperature shall be the sterilization temperature ±1 K (1 °C). Record the temperature at the centre of the test pack and in the chamber drain of the steam exposure apparatus.

NOTE 1 As the concentration of residual, induced or injected air or non-condensable gases within the standard test pack will not be predictably at the exact geometric centre, the additional temperature sensors in the standard test pack are used to improve the reproducibility of the test results.

NOTE 2 The precise volume of air required to produce a reference fault condition will vary from one steam exposure apparatus to another and with the method used to generate the reference fault condition.

C.2.4 Determine the amount of air needed to produce the reference fault condition, specified in Annex D, within the standard test pack, using the methods given in C.2.5.

C.2.5 Use the following conditions to produce a reference fault condition (see Annex D) and when testing the indicator.

a) Inject the volume of air into the chamber. The volume and the rate of injection should be determined by prior trial.

b) Determine the air leak into the chamber by the method given in EN 285. The rate of air leak required should be determined by prior trial.

c) Modify the air removal stage. The reduction in the pressure range and, if necessary, in the number of pulses in the air removal stage, should be determined by prior trial.

C.2.6 Repeat test three times for each of three separate production batches of the indicator.

C.2.7 After each test, inspect the indicator for conformance with 7.1 b).

1. 
   (normative)
   
   Reproducibility and determination of the reference fault condition in the standard test pack
   1. General

It is necessary to create a standard set of operating conditions that can be shown reproducibly to yield the desired results within a standard test pack for both the no-fault (pass) condition as well as the reference fault condition (fail condition).

Although many of the variables of the operating cycle for the steam exposure apparatus can be controlled with great precision, the key variable, i.e. the disposition of air within the chamber and load, is the least amenable to control, the least stable, and cannot be independently measured simultaneously.

NOTE No difficulty should be experienced in producing operating cycles which show satisfactory steam penetration in a standard test pack. It is only when air is present that it becomes less predictable.

A statistical basis is required so that, with the minimum number of cycles and a suitable means to measure variability, appropriate acceptance criteria can be determined:

a) for operating cycles intended to produce satisfactory steam penetration;

b) for operating cycles intended to produce a reference fault condition.

• 1. Criteria for acceptability of operating cycles
     1. General

Use the conditions described in D.2.2 and D.2.3 as the limiting conditions within which the temperature trace from the standard test pack shall lie. For each operating cycle, these criteria shall be met. In addition, by integrating the area between the chamber reference temperature and the test pack temperature for the hold period, it is possible to calculate the reference integrated fault (RIF) which provides a simple means of comparing cycles [see D.2.2 j)].

• • 1. Reference fault condition

For cycles to evaluate the ability of the indicator to detect inadequate steam penetration, the results of thermometric monitoring of the steam exposure apparatus and the standard test pack shall meet the following criteria as shown in Figure D.1.

a) The operating cycle, including the steam admission stage, shall meet all the criteria given in Annex C.

b) The elapsed time between the chamber attaining the set operating pressure and the chamber reference temperature attaining the set temperature shall not exceed 5 s. In a correctly functioning steam exposure apparatus, any difference should be due solely to the difference in response time of the pressure and temperature sensors.

c) At the time the chamber reference temperature, T_c, attains the set temperature, T_r, the temperature measured in the standard test pack, T_p, shall show a temperature depression, (T_c − T_p), of 2 K (2 °C) or greater.

d) The temperature depression shall remain at 2 K (2 °C) or greater throughout the reference fault period.

e) The test equilibration time shall be 90 s.

f) The temperature depression, (T_c − T_p), at the beginning of the reference fault period shall be no greater than 7 K (7 °C).

g) The temperature depression, (T_c − T_p), at the end of the reference fault period shall be no greater than 4 K (4 °C).

h) The temperature depression, (T_c − T_p), at the end of the minimum permitted equilibration time shall be no greater than 2 K (2 °C).

i) The temperature depression, (T_c − T_p), at the end of the exposure time or 10 min, whichever is shorter, shall be no greater than 1 K (1 °C).

j) The Reference Integrated Fault (RIF), determined as the area bounded by the trace of the chamber reference temperature, T_c, and the temperature at the centre of the standard test pack, T_p, shall be between 120 s⋅K and 525 s⋅K for a cycle at 134 °C for 3,5 min, and 120 s⋅K and 1 080 s⋅K for a cycle at 121 °C for 15 min.

k) The steam entry rate shall be 100 kPa/min to 250 kPa/min.

• • 1. No fault condition

A “no fault” cycle (pass condition) is one in which all indicators would be expected to provide evidence of a satisfactory cycle. The operating cycle to evaluate the ability of the indicator to detect adequate steam penetration and the results of thermometric monitoring of the steam exposure apparatus and the standard test pack shall meet the following criteria, as shown in Figure D.1.

a) The operating cycle, including the steam admission stage, shall meet all the criteria given in Annex B.

b) The elapsed time between the chamber attaining the set operating pressure and the chamber reference temperature attaining the set temperature shall not exceed 5 s. In a correctly functioning steam exposure apparatus, any difference should be due solely to the difference in response time of the pressure and temperature sensors.

c) At the time, t₁, at which the chamber reference temperature, T_c, attains the set temperature, T_r, the temperature measured in the standard test pack, T_p, shall show a temperature depression, (T_c − T_p), of 1 K (1 °C) or less.

d) By the end of the reference fault period there shall be no detectable temperature difference between the centre of the test pack, T_p, and the chamber reference temperature, T_c, (within the limits of accuracy of the measuring equipment).

Key

1 reference fault period

T_r set temperature

T_s minimum value of T_p at the time t₁ (“no fault” condition) (T_r − 1)

T_f maximum value of T_p at the time t₁ and t₂ (“fault” condition) (T_r − 2)

T_m minimum value of T_p at the time t₁ (“fault” condition) (T_r − 7)

T_x minimum value of T_p at the time t₂ (“fault” condition) (T_r − 4)

T_p temperature at the centre of the standard test pack

T_c chamber reference temperature

t₁ time at which the chamber reference temperature attains set temperature, T_r

t₂ end of the reference fault period = (t₁ + 30) s

t₃ end of the minimum permitted test equilibration time = (t₁ + 90) s

t₄ end of the set exposure time

A_F area within which the plot of the test pack temperature, T_p, shall lie for a “fault” condition

A_G area within which the plot of the test pack temperature, T_p, shall lie for a “no fault” condition

A_H area within which the plot of the test pack temperature, T_p, would indicate failure to obtain a correctly defined cycle for either “fault” or “no fault” conditions

Figure D.1 — Reference fault condition

• 1. Statistical evaluation of reproducibility

D.3.1 Run ten consecutive cycles on each of two days.

D.3.2 From the cycle records confirm that each cycle meets the acceptance criteria and determine the value of the Reference Integrated Fault. [See D.2.2 j).]

D.3.3 Calculate the mean and estimate of variance of the Reference Integrated Fault for the two sets of runs. It is not necessary to assume, or demonstrate, that the data are normally distributed (Gaussian). Using the F statistic shows this is not critical since the test is robust.

D.3.4 Carry out the F test (variance ratio test):

(E.1)

with (n₁ − 1) and (n₂ − 1) degrees of freedom.

Standard F tables are drawn up for 1-sided hypothesis, so for H₁ (variance_day1) = (variance_day2) and α = 0,05, the upper limit is given by δ₁/δ₂ and (n₁ − 1) and (n₂ − 1) degrees of freedom, and the lower limit is given by δ₂/δ₁ and (n₂ − 1) and (n₁ − 1) degrees of freedom.

D.3.5 Compare the calculated value of F with the critical region obtained from the tabulated values of F. The same tables can also be used to calculate the confidence interval.

1. 
   (normative)
   
   Determination of indicator colour change on exposure to dry heat
   1. Apparatus

E.1.1 Dry heat oven, capable of maintaining a temperature of (140 ± 2) °C.

NOTE This test is intended to provide a low relative humidity throughout the test period, normally below 5 % RH.

E.2.2 Two stainless steel plates, approximately 200 mm × 100 mm and of 2 mm nominal thickness and covered with material of the standard test pack.

• 1. Procedure
     1. General

Test both samples three times for each of three separate production batches of the indicator. Several test samples may be exposed simultaneously.

• • 1. Test

E.2.2.1 Pre-heat the oven to the operating temperature.

E.2.2.2 To prepare the test pieces, remove two 200 mm × 100 mm portions of the indicator system from the test sheet, place one centrally on each of the two test plates, and secure them in position by a strip of high- temperature-resistant adhesive tape at each corner.

E.2.2.3 Place the test pieces horizontally in the oven and subject them to dry heat at (140 ± 2) °C for a minimum time of 30 min. Remove the test pieces and examine them for colour change.

1. 
   (normative)
   
   Determination of shelf life of indicators

F.1 The testing of the product for determination of the shelf life shall be performed in accordance with a written protocol which shall be established before the commencement of the study.

NOTE National or regional regulation can contain additional or different requirements. Conformance with quality management International Standards (in particular ISO 9001 and ISO 13485) could require additional or different provisions.

F.2 The samples of the product shall be stored in their normal packaging at or above the maximum temperature and relative humidity recommended for storage. These conditions shall be controlled and monitored.

F.3 All performance requirements shall be met during and on completion of the storage period. This shall be verified by testing.

F.4 Conformance is verified by inspection of the technical documentation.

1. 
   (normative)
   
   Determination of transfer of indicator to standard test pack on processing
   1. Apparatus

G.1.1 Stainless steel plate, approximately 200 mm × 100 mm and of 2 mm nominal thickness, covered with material of the standard test pack.

G.1.2 Samples of chemical indicator, cut to approximately 200 mm × 100 mm

G.1.3 Steam exposure apparatus, as specified in Annex H.

G.1.4 Steam supply, as specified in EN 285.

G.1.5 Temperature-recording instruments, as specified in the requirements for test instrumentation given in EN 285.

• 1. Procedure

G.2.1 Centre a cut sample of the chemical indicator on the material-covered steel plate, with the indicator reagent uppermost. Place a second piece of material on the indicator system and secure it by taping along all sides to ensure intimate contact with the indicator system.

G.2.2 Place the assembly horizontally, with the steel plate as the lowest layer, in the steam exposure apparatus and subject it to dry saturated steam at 121 for 30 min.

G.2.3 Remove both layers of material and visually examine it for ink stains.

G.2.4 Repeat this test five times for three separate production batches of the indicator.

1. 
   (normative)
   
   Steam exposure apparatus and steam for test purposes
   1. General

H.1.1 The steam exposure apparatus shall consist of a steam sterilizer for wrapped goods and porous loads conforming with the requirements of EN 285, having a usable chamber space of not less than 250 l and not greater than 750 l, and conforming with the additional requirements for cycle control specified in this annex.

H.1.2 The control system shall allow the simulation of the porous load sterilization cycles currently operated on machines of different provenance, with a high level of reproducibility on replicate runs of the same cycle.

• 1. Instrumentation
     1. General

The instrumentation shall conform with 6.4.1, 6.4.2, and 6.4.3 of EN 285:2015+A1:2021.

• • 1. Indicator, controller and recorder sensors

The recorder shall be independent of the automatic controller.

A common system for indication, control and recording may be used provided that a minimum of two sensors are employed for each location and variable to be considered, and that the system is self-monitoring such that any error in the measured variable in excess of the accuracy specified shall result in the indication of a fault.

• • 1. Calibration

The equipment used for measurement of temperature and pressure shall be in a known state of calibration.

This shall include verification of calibration before and after each series of tests. A series of tests shall comprise all the tests required to investigate conformity of a product with this document.

Test results obtained after satisfactory verification of calibration, but for which subsequent verification of calibration, after completion of testing, demonstrates that the test equipment was outside specified limits, shall not be used for demonstration of conformity with this document.

• 1. Cycle control
     1. Steam control

Means shall be provided to enable the steam in the chamber to be maintained at the selected operating pressure ±2 kPa.

• • 1. Air detector

If an air detector is fitted, isolation of the air detector from cycle control shall be a cycle programme option.

• • 1. Signals

Means shall be provided to generate signals capable of being used automatically to initiate the operation of ancillary equipment (e.g. air injection apparatus) on attainment of a programmable value for temperature at the reference measurement point of the chamber temperature, chamber pressure or elapsed time at any chosen point during the air removal, steam admission or hold stages.

• 1. Operating cycle stages and control limits required
     1. Cycle stages

The automatic controller shall provide a means to select and adjust each of the following cycle stages:

a) evacuation: to effect the initial stages of air removal, an ultimate pressure of ≤ 4,5 kPa shall be attainable;

b) air removal: by alternate steam admission and evacuation of the chamber;

The pressure range shall be adjustable to provide both sub-atmospheric and super-atmospheric pulsing; the number of pulses shall be adjustable to provide the option to select between 0 and not less than 8 pulses;

c) steam admission to pre-set exposure conditions [see 7.1 a) and 7.1 b)];

d) exposure time: the pressure shall be controlled throughout the hold period within ±2 kPa of the set operating pressure;

e) evacuation: to remove steam (thus ending the indicator reaction) and also to dry the load, an ultimate pressure ≤ 5 kPa shall be attainable;

f) air admission: to equilibrate the chamber pressure with atmospheric pressure.

• • 1. Control limits

H.4.2.1 Pressure-attained control points shall be capable of being attained reproducibly to within ±1,0 kPa over the range 4 kPa to 16 kPa and ±2,0 kPa over the range 16 kPa to 385 kPa.

H.4.2.2 Elapsed-time control points shall be capable of being attained reproducibly to an accuracy of ±1 s over the range 2 s to 60 min.

H.4.2.3 Temperature-attained control points shall be capable of being attained reproducibly to an accuracy of ±0,5 K (0,5 °C) over the range 50 °C to 145 °C.

H.4.2.4 The rate of pressure change during steam admission shall be within 100 kPa/min to 250 kPa/min.

H.4.2.5 The rate of pressure change during evacuation shall be adjustable up to at least 400 kPa/min.

• 1. Steam supply

H.5.1 Particular attention shall be paid to the levels of non-condensable gases in the steam supply and to ensuring that the moisture content or superheating of the steam is within the specified limits, even under the extremes of the steam demand generated by the steam exposure apparatus and any other equipment connected to the same steam supply. The steam shall contain not more than 3,5 % (volume fraction) of non-condensable gases when tested as specified in 21.1 of EN 285:2015+A1:2021. The dryness value of the steam shall be not less than 0,95 when tested as specified in 21.2 of EN 285:2015+A1:2021. The degree of superheat measured in free steam at atmospheric pressure shall not exceed 25 K. Conformance shall be tested as specified in 21.3 of EN 285:2015+A1:2021.

H.5.2 The condensate obtained from steam supplied to the chamber of the steam exposure apparatus shall conform with the following requirements, unless the manufacturer can demonstrate that any of the specified contaminants, when present at higher concentrations, do not influence the performance of the indicator or indicator system:

a) conductivity: ≤ 15 µS/cm;

b) pH-value: 5 to 8.

The pH-value can be monitored by a chemical colour indicator such as a paper strip or solution. Other interfering substances, e.g. phosphate, chloride, sulfate, oxidizable substances, shall be identified by the manufacturer and stated in the labelling.

1. 
   (normative)
   
   Standard test pack

I.1 This text is based on EN 285:2015+A1:2021, 23.1, however, the tolerances have been modified to improve reproducibility.

I.2 The test pack shall be composed of plain cotton sheets, each bleached to a good white and having approximate dimensions of 900 mm × 1 200 mm. The number of threads per centimetre in the warp shall be 30 ± 6 and the number of threads in the weft 27 ± 5, the areic mass shall be (185 ± 5) g/m2; edges which are not selvedges shall not be hemmed.

I.3 The sheets shall be washed when new or soiled and should not be subjected to any fabric conditioning agent during laundering. Fabric conditioning agents can affect the characteristics of the fabric and can contain volatiles which contribute to the non-condensable gases in the sterilizer.

I.4 The sheets shall be dried and then allowed to equilibrate in an environment of between 20 °C and 30 °C and a relative humidity of 40 % to 60 %.

I.5 After equilibration, the sheets shall be folded to approximately 220 mm × 300 mm and stacked to a height of 250 mm after compression by hand. The pack shall be wrapped in a similar fabric and secured with tape not exceeding 25 mm in width. The total mass of the pack shall be 7,0 kg ± 2 % (approximately 30 sheets are required for this). The pack shall be exposed to four consecutive cycles in the steam exposure apparatus using the operating cycle described in B.2. After processing, the pack shall be removed from the sterilizer and aired in an environment of between 20 °C and 30 °C and relative humidity of between 40 % and 60 %. The pack may then be used for testing. The pack shall be equilibrated in an environment of between 20 °C and 30 °C and relative humidity of between 40 % and 60 % between uses. Packs which are not used within 1 h of preparation can be stored in the workroom, providing the environmental conditions are maintained within the limits specified above.

After use, the sheets will become compressed. When the mass of sheets used to form a stack 250 mm high exceeds 7,14 kg, the sheets should be discarded.

I.6 Prior to use, the temperature and humidity of the pack shall be measured using a suitable calibrated temperature and humidity probe. The conditions within the pack shall be between 20 °C and 30 °C and 40 % and 60 % relative humidity before it is used for test purposes. Pack temperature and humidity may be measured using a sword hygrometer.

1. 
   (normative)
   
   Air injection system

J.1 The air injection system shall consist of the following components:

a) a double-acting air cylinder;

b) a charging circuit designed to allow one side of the piston to be pressurized with air at a predetermined pressure in the range 100 kPa to 1 000 kPa;

c) an adjustable limit stop to restrict the travel of the piston to a predetermined position during charging to provide control of the charge volume;

d) a driving circuit designed to allow pressurization of the uncharged side of the piston in order to drive the air charge into the steam exposure apparatus chamber at the required rate;

e) a connecting circuit to the steam exposure apparatus incorporating a flow-regulating device for fine control of the rate of air discharge and a terminal valve to isolate the injection apparatus from the steam exposure apparatus.

The system should be provided with a means to prevent the ingress of steam from the steam exposure apparatus.

Means should be provided to ensure that the charging circuit is effectively isolated from the air cylinder before the terminal valve can be opened. Failure to do so will allow uncontrolled air admission to the chamber of the steam exposure apparatus. The volume of air admitted can be controlled by changing either the stroke length or the charging pressure or both.

J.2 The volume of air discharged at various combinations of pressure and stroke length shall be calibrated by collection of the discharged gas by downward displacement of water at atmospheric pressure and measurement of the volume of water displaced.

J.3 The air injection rate and the location within the chamber shall be validated and documented to provide the required reproducibility (see Annex D).

J.4 Figure J.1 shows an example schematic layout of a suitable air injection apparatus. Other similar arrangements can be suitable.

Key

Figure J.1 — Example of schematic layout of air injection apparatus

1. 
   (informative)
   
   Relationship between chemical indicator components

Key

1 chemical indicator reagent

2 substrate

3 chemical indicator to be used as is

4 chemical indicator to be used only with a specified test load

5 specified test load

6 chemical indicator system

Figure K.1 — Relationship of chemical indicator components (derived from ISO 11140-1:2014, Annex E)

Annex ZA
(informative)

Relationship between this European Standard and the General Safety and Performance Requirements of Regulation (EU) 2017/745 aimed to be covered

This European standard has been prepared under M/575 to provide one voluntary means of conforming to the General Safety and Performance Requirements of Regulation (EU) 2017/745 of 5 April 2017 concerning medical devices [OJ L 117] and to system or process requirements including those relating to quality management systems, risk management, post-market surveillance systems, clinical investigations, clinical evaluation or post-market clinical follow-up.

Once this standard is cited in the Official Journal of the European Union under that Regulation, compliance with the normative clauses of this standard given in Table ZA.1 and application of the edition of the normatively referenced standards given in Table ZA.2 confers, within the limits of the scope of this standard, a presumption of conformity with the corresponding General Safety and Performance Requirements of that Regulation, and associated EFTA Regulations.

Where a definition in this standard differs from a definition of the same term set out in Regulation (EU) 2017/745, the differences shall be indicated in this Annex Z. For the purpose of using this standard in support of the requirements set out in Regulation (EU) 2017/745, the definitions set out in this Regulation prevail.

Where the European standard is an adoption of an International Standard, the scope of this standard can differ from the scope of the European Regulation that it supports. As the scope of the applicable regulatory requirements differ from nation to nation and region to region, the standard can only support European regulatory requirements to the extent of the scope of the European regulation for medical devices (EU) 2017/745).

NOTE 1 Where a reference from a clause of this standard to the risk management process is made, the risk management process needs to be in compliance with Regulation (EU) 2017/745. This means that risks have to be ‘reduced as far as possible’, ‘reduced to the lowest possible level’, ‘reduced as far as possible and appropriate’, ‘removed or reduced as far as possible’, ‘eliminated or reduced as far as possible’, ’removed or minimized as far as possible’, or ‘minimized’, according to the wording of the corresponding General Safety and Performance Requirement.

NOTE 2 The manufacturer’s policy for determining acceptable risk must be in compliance with General Safety and Performance Requirements 1, 2, 3, 4, 5, 8, 9, 10, 11, 14, 16, 17, 18, 19, 20, 21 and 22 of the Regulation.

NOTE 3 When a General Safety and Performance Requirement does not appear in Table ZA.1, it means that it is not addressed by this European Standard.

Table ZA.1 — Correspondence between this European standard and Annex I of Regulation (EU) 2017/745 [OJ L 117] and to system or process requirements including those relating to quality management systems, risk management, post-market surveillance systems, clinical investigations, clinical evaluation or post-market clinical follow-up

Table ZA.2 — Normative references from clause 2 of this document and their corresponding European publications

The documents listed in the Column 1 of table ZA.2, in whole or in part, are normatively referenced in this document, i.e. are indispensable for its application. The achievement of the presumption of conformity is subject to the application of the edition of Standards as listed in Column 4 or, if no European Standard Edition exists, the International Standard Edition given in Column 2 of table ZA.2

WARNING 1 — Presumption of conformity stays valid only as long as a reference to this European Standard is maintained in the list published in the Official Journal of the European Union. Users of this standard should consult frequently the latest list published in the Official Journal of the European Union.

WARNING 2 — Other Union legislation may be applicable to the product(s) falling within the scope of this standard.

Bibliography

[1] Bowie J.H., Kelsey J.C., Thompson G.R. The Bowie and Dick autoclave tape test. Lancet. 1963, 281 (7281) pp. 586-587

[2] ISO 17665, Sterilization of health care products — Moist heat — Requirements for the development, validation and routine control of a sterilization process for medical devices

[3] ISO 15882, Sterilization of health care products — Chemical indicators — Guidance for selection, use and interpretation of results

[4] ISO 13485, Medical devices — Quality management systems — Requirements for regulatory purposes

[5] ISO 5‑1, Photography and graphic technology — Density measurements — Part 1: Geometry and functional notation

[6] ISO 5‑3, Photography and graphic technology — Density measurements — Part 3: Spectral conditions

[7] ISO 5‑4, Photography and graphic technology — Density measurements — Part 4: Geometric conditions for reflection density