GB2333360A

GB2333360A - Steriliser test sheet

Info

Publication number: GB2333360A
Application number: GB9900947A
Authority: GB
Inventors: Beverley Victor Pitman
Original assignee: Rexam Medical Packaging Ltd
Current assignee: Amcor Flexibles Winterbourne Ltd
Priority date: 1998-01-15
Filing date: 1999-01-15
Publication date: 1999-07-21
Also published as: GB9800877D0

Abstract

The sheet 10 e.g. for use in the Bowie Dick test for sterilisers, has first portion 12 with a printed pattern 18 of indicator ink, and a second portion 14 folded over to cover the pattern 18. The folded sheet is incorporated with a test load, generally a pack of cotton sheets. The covering portion 14 protects the load from ink transfer. The sheet 10 is sufficiently porous that the double thickness does not impair the reliability of the test.

Description

STERILIZER TEST SYSTEM The present application relates to a method and apparatus for use in testing sterilizers (e.g large porous-load steam sterilizers with pre-sterilisation vacuum extractors for medical equipment).

A known test system makes use of "The Bowie Dick Test sheet".

This consists of a sheet of porous paper which has a special indicator ink, printed in a certain pattern, which changes completely from its initial presterilisation colour to its specified post-sterilisation colour when predetermined conditions (dry steam above a threshold temperature)are met inside the sterilizer. If for example the steriliser chamber has not had all the air removed the remaining air tends to accumulate in the centre of the chamber or test load (which is designed to cause the air to form into a spherical bubble at its centre) and the presence of this air prevents the correct temperature being achieved. Thus the ink pattern in the centre changes colour to a lesser extent than on the periphery. This difference and its extent can be used to estimate the size of the functional failure of the steriliser.

The Bowie Dick test is conducted by placing one of the test sheets in a test load, namely a pack of special cotton sheets which allows the steam and heat to penetrate and thus simulates a load requiring to be sterilised. There is a European Standard for this indicator system and it specifically stipulates that there must be no ink transfer from the test sheet to the cotton sheets. This places considerable constraints on the indicator ink, in addition to those associated with the need for reliable indicator behaviour.

Thus in one aspect we provide a test sheet, e.g for a sterilizer, having a first portion and a second portion, the sheet being folded or foldable so that the first portion overlies the second portion; at least one of the portions bearing indicator ink arranged so that it is covered by the folded-over other portion.

In a second aspect we provide a test load for a sterilizer including a folded test sheet according to the first aspect. The load may comprise a stack of porous sheets (e.g. plain cotton sheets as specified in European Standard EN 867-3), with the test sheet incorporated into its centre. The folded test sheet must be able to perform similarly to a folded porous sheet of the stack, so that the behaviour of air is not substantially affected.

In a third aspect we provide a method of testing a sterilizer, using a test load according to the second aspect or a test sheet according to the first aspect.

An embodiment of the invention will now be described with reference to the according drawings in which: Fig 1 is a plan view of one face of a test sheet embodying the invention, opened out; and Fig 2 is a like view showing the other face; and Fig 3 is a schematic elevation of the sheet folded ready for use.

The illustrated sheet 10 is rectangular and is divided into two almost-equal parts or portions 12, 14 by a fold line 16. A first portion 12 (which is slightly larger in this example) bears a pattern 18 formed in indicator ink. The nature and material of the pattern and ink may be generally conventional, and preferably conform to European Standard EN 867-3 (specification for class B indicator for use in the Bowie and Dick test).

The sheet 10 must be porous. It is generally of paper. Generally it should be at least as porous as the requirement set out in EN 867-3. That is, its porosity in the form in which it is to be used (i.e. folded) is desirably greater that 3.4m/Pa.s when tested in accordance with ISO 5636-3 at an air pressure of 1.47 kPa.

The sheet may bear indicia 20, e.g. including indicia indicating data to be filled in, preferably on the second portion 14 (which does not bear indicator ink in this example).

The indicator ink is desirably completely stable after sterilisation. Thus a sheet which has been used and on which data have been filled in can easily be stored to provide a permanent record of est on a steriliser. Punched holes 22 to fit a standard ring binder are provided to assist, on the marginal portion 24 which projects beyond the small second portion 14.

Claims

CLAIMS 1. A test sheet for a sterilizer, said sheet having a first portion and a second portion, the sheet being folded or foldable so that the first portion overlies the second portion; at least one of the portions bearing indicator ink arranged so that it is covered by the folded-over other portion.
2. A test sheet according to claim 1 wherein a said portion bearing indicator ink bears ink in the form of a pattern and conforms to the European Standard EN 867-3 for a class B indicator for use in the Bowie and Dick test.
3. A test sheet according to claims 1 or claim 2 wherein the porosity of the folded sheet is greater than 3.4 ym/Pa.s when tested in accordance with ISO 5636-3 at an air pressure of 1.47 kPa.
4. A test sheet according to any preceding claim wherein the portions are of unequal sizes such that, in the folded state, there is a projecting single-ply marginal portion; and wherein said marginal portion is perforated to facilitate filing of the folded sheet.
5. A test sheet substantially as herein described with reference to and as illustrated in the accompanying drawings.
6. A test load for a sterilizer including a folded test sheet according to any preceding claim.
7. A test load according to claim 6 wherein the load comprises a stack of porous sheets with the test sheet incorporated into its centre.
8. A test load substantially as herein described with reference to and as illustrated in the accompanying drawings.
9. A method of testing a sterilizer, using a test load according to any of claims 6 to 8 or a test sheet according to any of claims 1 to 5.
10. A method according to claim 9 which is in accordance with European Standard EN 867-3.
11. A method of testing a steriliser substantially as herein described with reference to and as illustrated in the accompanying drawings.