GB2176435A - Handling toxic materials - Google Patents

Abstract

A toxic-specimen examination enclosure comprises: (i) a closed envelope 12 which defines within itself an examination chamber, and which incorporates- - normally-closed port means 42,82 through which toxic specimens may be introduced into and/or expelled from said chamber, - operative's flexible gloves 44 extending through and secured in a gas-tight manner in apertures formed in the envelope, for enabling objects within said chamber to be manipulated by an operative outside the enclosure, and - a portion 88 thereof that is yieldable relative to the other parts of said envelope; and (ii) a microscope disposed within said chamber and having at least one eyepiece 86 that is movable relative to a stationery specimen platform of the microscope for adjusting the focus of the microscope, which eyepiece extends through and is secured in a gas-tight manner in an aperture formed in said yieldable portion 86 of said envelope, so that said eyepiece and the adjoining parts of said yieldable portion move together when the focus of said microscope is being adjusted. A second chamber 10 may be used for preparing a specimen slide eg of asbestos for viewing by the microscope, and there may be a further examination chamber (figure 6, not shown) also comprising a microscope. <IMAGE>

Description

SPECIFICATION Handling toxic materials This invention relates to methods of and apparatus for handling toxic materials that require microscopical examination, particularly dust-forming fibrous materials (such as for example, asbestos materials) and pathogens.

Some dust-forming fibrous materials are now known to be especially dangerous to mankind, in view of their capacity to initiate the development of carcinomas. This is particularly so in respect of various kinds of asbestos. Asbestos materials have been widely used in the past as insulation against heat and sound, but now those suspect materials are being removed for disposal whereby to minimise the exposure of human beings to such materials.

It is desirable that before any suspect insulation or other potentially dangerous building material of a fibrous nature is designated for removal from a building, it should be positively identified as being one that is known to be dangerous. Thus, it is now common practice to send a sample of a suspect material to a suitable laboratory for identification before taking any other action in respect of the material.

Laboratories receiving such samples have, likewise, a need to handle with due care all such samples submitted to them for examination and identification, so as to protect their staff from such dust hazards.

Currently, glove boxes are normally available in such laboratories for handling such dust-forming fibrous materials, and comprise a rigid panel construction in which gloves are let into a lower front panel, and an upper front panel is transparent so as to give an operator a full view of the operations being performed by his gloved hands within the confines of the box. Such boxes may be provided with air extraction means for withdrawing air and air-borne debris from within the box.

Glove boxes currently available are relatively expensive, and are not particularly well suited to the safe handling of samples of asbestos and similar materials submitted for microscopic examination and identification.

In particular, they have no facilities for enabling such a sample to be examined and identified under a microscope whilst the sample is still enclosed within the glove box.

Isolation cabinets useful in the handling of dangerous organisms and materials in the biological and medical fields are known. Such cabinets have comprised an air-tight enclosure made from a welded, flexible thermo-plastics sheet material, which enclosure has been carried on and supported by a shape-defining framework which is fitted wholly within the enclosure. Air supply and extraction means penetrate the enclosure, and a net negative pressure has been maintained in the enclosure to prevent the egress of organisms and materials from the enclosure into the surrounding atmosphere. Observation panels in the enclosure have been made from a transparent material.

Likewise, such isolation cabinets have no facilities for enabling a specimen to be examined and identified under a microscope whilst the specimen is enclosed within the cabinet.

For our examination (in private) of samples of fibrous materials received for examination and identification, we have specially modified a glove box so as to render possible the microscopical examination and identification of samples whilst still enclosed in that modified glove box. In a initial phase of our procedure, each such sample has been admitted to that experimental glove box, and whilst therein a small specimen of the sample has been separated therefrom and loaded into a small container such as a Petri dish.

In a second phase of the procedure, also carried out in that glove box, that specimen has been examined under a stereoscopic microscope to select therefrom suitable elements of the specimen for treatment with appropriate refractive index liquids and incorporation in one or more microscope slides. Unfortunately, problems of contamination of the equipment enclosed within the glove box arising from the relatively dirty initial phase have not permitted the carrying out in that glove box of the final phase of treating the selected elements and incorporating them in such slides. Hence, the selected elements have been treated and incorporated in slides whilst disposed outside that glove box.

Thus, during this final phase, the operator has been exposed to an atmosphere into which dust from those elements could be released, and with which atmosphere that air-borne dust could be inhaled by the operator.

During the afore-mentioned initial phase carried out in the glove box, a further specimen has been heat-sealed in a thermoplastics envelope and then removed from the glove box for record purposes, whilst the remainder of the sample has been placed in a debris collection bag, sealed therein, double bagged, and then removed for disposal.

Various aspects of the present invention will become apparent from the claims appended at the end of this description, and from what follows hereafter.

According to one of those various aspects of the present invention, both said initial and subsequent phases of handling a sample and preparing therefrom one or more microscope slides are carried out in a closed enclosure means from which air is continuously extracted; said initial phase being carried out in a first constituent enclosure and a specimen of said sample being transferred in a closed container through a normally-closed transfer duct to a second constituent enclosure, and the said subsequent phases being carried out in said second enclosure using a stereoscopic microscope which is permanently housed in that enclosure and which has eye-pieces that penetrate the wall of that enclosure in an air-tight manner; the sample being admitted to the first enclosure and the residue thereof being expelled therefrom through normally-closed ports, and the slide making materials likewise being admitted to said second enclosure and the finished microscope slides being expelled therefrom through normally-closed ports.

According to another aspect of the present invention, in said enclosure means said first and second enclosures are disposed end to end and interconnected at juxtaposed ends thereof by said normally-closed transfer duct; said first enclosure being provided with said normally-closed ports for admitting each said sample and for expelling the enclosed residue thereof; said second enclosure being provided with said normally-closed port for admitting said slide making materials and expelling said finished microscope slides; each such enclosure being provided with an air extraction duct through which air may be drawn from the enclosure; and each such enclosure being provided in at least its front panel with air-tight operative's gloves, with which gloves an operative may handle articles and materials enclosed within said enclosure.

Alternatively, if desired, said final phase may be carried out in a third constituent enclosure to which said selected elements may be transferred from said second constituent enclosure. Said third enclosure may, like said second enclosure, contain a stereoscopic microscope for use in treating and incorporating such selected elements in microscope slides.

Each said enclosure may comprise an envelope made of a rigid plastics sheet material, such as a transparent acrylic material.

Alternatively, each said enclosure may comprise an envelope made of a soft, flexible thermo-plastics sheet material, which material is preferably transparent, and which material has any necessary seams joined together preferably by a heat sealing process.

In the latter case, each of the enclosures may be provided with a shape-defining framework which is disposed wholly, or at least in part, outside a said envelope of thermo-plastics sheet material, from which framework said envelope is suspended wholly or in part by means of loops fitted externally to said envelope. Such a framework may conveniently comprise two end frames which are disposed outside the associated envelope and which are spaced apart by transverse members which penetrate that envelope in an air-tight manner, said envelope being supported externally from said end frames by means of loops secured externally to said envelope, and internally by said transverse members.

Preferably, the frameworks of the respective enclosures are joined together by transverse spacer members which extend between the juxtaposed end frames of the respective enclosures and are secured thereto.

Apparatus according to the present invention enables the method according to the present invention to be carried out wholly in a controlled environment from which, for example, air-borne dust of a fibrous material sample cannot escape and be inhaled by an operator. Moreover, the relatively dirty operations performed in handling the samples are carried out in the first enclosure which is isolated from the second enclosure, so that the equipment in that second enclosure does not suffer contamination arising from the handling of the samples in the first enclosure.Hence, the microscope and slide forming materials in the second enclosure, or in the third enclosure, are subject to only relatively light contamination such as can arise from handling the small specimens that are transferred from the first enclosure, or from the second enclosure respectively, so that the examination of that specimen and the making of the slides is carried out in a relatively clean environment.

Other features of the present invention will appear from the description that follows hereafter, and from the claims that are appended at the end of that description.

One asbestos sample-handling/examination and slide-making equipment embodying the present invention, and-various modifications thereof, will now be described by way of example and with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows a perspective view of the equipment; Figure 2 shows a front view of the equipment; Figures 3 and 4 show end views looking respectively on the right and left hand ends of the equipment as seen in the Figure 2; Figure 5 shows a perspective view of the left hand end of a framework that is incorporated in the equipment; and Figure 6 shows a rigid enclosure shell for use in an alternative form of said equipment.

Referring now to the Figures 1 to 5, the equipment there shown comprises two generally similar enclosures 10, 12, each of which comprises a closed, substantially air-tight envelope 14, 16 formed by thermally welding together shaped pieces or panels of a soft, flexible, transparent thermo-plastics sheet material such as polyethylene. Each such envelope is mechanically supported by a metal (preferably aluminium) framework 18, 20 of tubular frame members 22, and the two frameworks are rigidly coupled together by metal transverse spacer members 24.

Each such framework 18, 20 comprises two rigid end frames 26, 28 which are spaced apart by transverse frame members 30. The interconnections of the various frame and spacer members are made by means of bolt and nut fixing devices 32 which secure the splayed ends 34 of the respective members together.

Each envelope is provided at each of its ends with (a) a series of through-bushes 36 which penetrate the end panel of the envelope and through which the transverse frame members 30 extend into and out of the envelope, and (b) a series of elongated loops 38 welded to the end panel and through which the respective members of the adjacent end frame are threaded. Thus, the end frames provide supportfor the envelope externally of the respective end panels, whilst the transverse frame members provide support for the envelope inter nally between those end panels.

Each enclosure is totally transparent, so that everything within the enclosure is plainly visible to an operator using the equipment.

The two enclosures are interconnected by a large diameter plastics tube 40 which penetrates and is sealed in an airtight manner in the juxtaposed end panels of the respective enclosures. That tube constitutes a transfer channel or duct for effecting transfer of articles and materials between the two enclosures, and each end of that tube is provided with an air and dust tight closure cap 42.

Operatives gloves 44 are let into and sealed in an air and dust tight manner in the lower front panels and the respective end panels of each enclosure so as to enable an operator to handle articles, apparatus and materials disposed within the enclosures.

The rear panel of each enclosure incorporates in an upper part thereof a zip-type fastener 46 which opens and closes in an airtight manner a transverse access slit formed in the rear panel and through which apparatus (for example, a heat sealing apparatus for use in sealing plastics envelope material in the first enclosure) to be installed in the enclosure can be passed.

An air extraction pipe 48 extends along the rear upper part of each enclosure, and incorporates (a) a rotary type valve sleeve 50 for opening and closing a plurality of air ports formed in that pipe whereby to provide means for adjusting the rate of air extraction from the enclosure, and (b) a capped tee-connection 52 for receiving a vacuum cleaning pipe and nozzle (not shown) when required for cleaning out the enclosure. That air extraction pipe penetrates and is sealed in an air-tight manner in the respective end panels of the enclosure, being closed at one end by a removable closure cap 54 and being connected at the other end through a tee-connection 56 to a suction pipe 58 leading to an air extraction pump (not shown).

Each enclosure has mounted in in its right hand end panel an air filter 60 through which air may be drawn into the enclosure by the said extraction pump.

The left hand enclosure 10 (referred to later as the 'dirty enclosure') is provided in its respective top and bottom panels with two large diameter plastics tubes 62, 64 which constitute respectively a sample-admission duct, and a sample-disposal duct, each such tube being provided uppermost with a removable air and dust tight closure cap 66, 68. The sample-disposal tube has its lower end dipping into a package-decontamination water bath 70 contained within a slidable drawer 72 mounted beneath the dirty enclosure, whereby the encapsulated remainder of a sample can be passed via that tube to the atmosphere outside the dirty enclosure only by way of that bath of water.

A second plastics disposal tube 74 is also provided in the bottom panel of that enclosure, and that tube is intended to receive on its lower end, which extends below the enclosure, in concertinafashion a flexible waste disposal tube 76 which is sealed at its lower end, and into which other waste from the enclosure may be dropped and sealed off with a tie 78.

Teats 80 are provided in the lower part of the rear panel of each enclosure for enabling electric cables and other connections to pass through into the enclosure in an air-tight manner.

The right hand end panel of the right hand enclosure 12 (referred to later as the 'clean enclosure') has secured therein in an air-tight manner a plastics slide-exit tube 82, and each end of that tube is provided with a removable air and dust tight closure cap.

Disposed within the clean enclosure is a stereoscopic microscope 84, of which the respective vertically and transversely movable eyepieces 86 penetrate and are sealed in an air-tight manner in the upper, sloping, front panel 87 of that enclosure, which panel is provided with a locally projecting, yieldable portion 88 designed to accommodate those eye-pieces and to yield and move with those eyepieces when they are being adjusted.

That sloping front panel 87 is also provided with a plurality of outwardly projecting teats 90 for receiving in an air-tight manner liquid dropper tubes or nozzles (not shown) for delivering into the clean enclosure small quantities as required of 'refractive index' (or other) liquids which may be needed in the operations to be carried out in the clean enclosure.

A preferred method of using the equipment just described for the purposes of handling and making microscope slides from samples of asbestos materials is as follows: With the air extraction pump operative to extract air at a desired low rate from the two enclosures (a) a package containing a sample of an unidentified fibrous material is first admitted into the dirty enclosure via the sample-admission duct 62; (b) with the admission and exit tubes 62, 64, 74 and the transfer tube 40 all capped off, the package is opened, and the sample is extracted therefrom by the operator, using the gloves 44 of the enclosure, and is examined to establish, by means of the naked eye, firstly whether or not there is more than one layer present, and secondly, whether or not the sample is 'patched' (i.e. involves material from an original lagging material and a material applied subsequently as a patching material); (c) a representative specimen of the sample is then separated from the sample and placed in a Petri dish which is then closed, the remainder of the sample being then heat-sealed in one or more soft tubular envelopes of a thermo-plastics material, which sealed envelopes are then passed out of the dirty enclosure via the exit tube 64 and the water bath for record purposes, or via the disposal tube 74 into the waste disposal envelope 76 for disposal; (d) after completion of those dirty operations in the dirty enclosure, the closed Petri dish is transferred via the transfer tube 40 into the clean enclosure, that tube and its two closure caps being used in the manner of an air lock to prevent contamination of the clean enclosure by dust produced in the dirty enclosure by the handling there of the unpackaged sample; (e) the specimen in the Petri dish is then examined under the stereoscopic microscope, and representative elements of the sample are selected, treated with appropriate refractive index liquids (admitted from bottles outside the clean enclosure via droppers inserted through the teats 90 in the upper, sloping front panel of that enclosure), and then incorporated in microscope slides for further examination and identification in the environment outside the clean enclosure; (f) those slides are then transferred out of the clean enclosure into the environment outside via the slide-exit tube 82; (f) the remainder of the specimen is then returned in the closed Petri dish via the transfer tube 40 to the dirty enclosure, from whence it is expelled along with any other refuse produced in the operations via the exit tube 74 into the waste disposal envelope 76; and (g) dust deposited around the interiors of the two enclosures is vacuum cleaned away.

The equipment just described provides a means whereby (a) samples of dust-producing fibrous materials can be safely handled and disposed of after extracting representative specimens for incorporation in microscope slides, and (b) those specimens can be incorporated in such slides, all without sub jetting the operator to risk of contamination by dust inhalation.

Moreover, the equipment described provides a full view of all operations being carried out, and a minimum of permanent structure within the two enclosures on which dust freed from the samples as they are being handled can collect and be harboured. Furthermore, the operations to be carried out in clean handling conditions are isolated from the areas in which the preceding dirty operations were carried out.

In the present context the term 'dirty' is intended to mean: subject to or likely to be subjected to substantial contamination from dust present in or freed from fibrous materials being handled. On the other hand, the term 'clean' is intended to imply the converse.

In the equipment described above, the framework may be replaced, if desired, by one that is intended to lie wholly outside the enclosure, in which case the envelope is suspended from the framework by means of loops or elongated loops which are engaged (detachably if desired) around the respective frame members. Furthermore, the framework may be permanently secured together, in which case the enclosure is detachably suspended within the framework by loops as mentioned above. Alternatively, the end frames described above may be replaced, if desired, by other end frames in which the constituent frame mebers are permanently secured together. In that case, the enclosure is secured to the end frames by elongated loops that are detachably engaged around the members of those end frames.

If desired, the equipment so far described may also be modified so as to incorporate a third enclosure of construction generally similar to that of the first and second enclosures 10 and 12, the third enclosure being disposed on the side of the examination enclosure 12 remote from the sample preparation enclosure 10, and having a normallyclosed duct communicating with the examination enclosure 12. That third enclosure also incorporates (a) a normally-closed access opening for enabling microscope slides and other objects and materials to be moved into and out of that enclosure, and (b) a stereoscopic microscope having its respective eyepieces projecting externally of the enclosure wall and being secured therein.

This third enclosure is provided so that the selected elements of the representative sample which are to be treated and made up into slides may be handled in a still cleaner enclosure into which the operative's hands may penetrate directly without the use of gloves sealed into the wall of that enclosure. Such gloves tend to hamper the delicate operations that are necessary to treat and incorporate the selected elements into slides. For that purpose, the third enclosure is provided with a frontal access opening which is closed by a vertically hanging curtain which comprises a series of vertical strips of a flexible, preferable transparent, plastics material, which strips hang side-by-side and overlap one another so as to create a normally-closed barrier across said access opening.Such plastics strips may be readily pushed aside by the operative's hands to gain access to the third enclosure.

The materials used in the construction of the enclosures and their fittings may comprise plastics materials, and even the framework may comprise such a material provided sufficient strength is obtained to support the associated enclosure. However, a metal framework may be preferred.

It will be appreciated that the equipment described above constitutes a relatively safe, inexpensive, economical and adaptable apparatus for carrying out the operations described above. Moreover, the method of carrying out the operations described substantially reduces the hazards for those carrying out such operations.

Whereas the equipment so far described has utilised envelope material of a flexible sheet form, such equipment may alternatively be made of rigid plastics materials instead, preferably transparent materials. Such materials may comprise, for example, an acrylic material such as that commercially available under the trade mark PERSPEX.

A rigid shell for use in such a modified equipment is shown in the Figure 6, where for the sake of clarity only, some of the various fittings of the above described flexible enclosure equipment are not shown. In that Figure 6, the three rigid enclosures 200, 202, 204 are shown all bolted together as a single unit. In the sample preparation enclosure 200, the decontamination water bath 206 is shown as being formed within the confines of that enclosure rather than below it. Access for placing items of equipment in the enclosure is by way of a rear-hinged upper panel 208, and the sample admission duct 210 is provided lowermost with a trap door 212.

In the sample examination enclosure 202, access for introducing the microscope and other items of equipment is by way of a rear-hinged upper panel 214. A central frontal opening 216 is provided for accommodating the movable eyepieces (86) of the stereoscopic microscope (84) and these eyepieces are secured in and sealed to the peripheral parts of that opening 216 by means of a transparent bellows device 218 having an apertured frontal panel 220 through which the eyepieces penetrate. That bellows device allows movement of the eyepieces as they move up and down to adjust the focus of the microscope, and towards and away from'one another when adjusting the separation of them to the eye of an operative.

Connection with the slide preparation enclosure 204 is achieved by way of an opening 222 formed in the adjoining walls of the enclosures 202 and 204, once a slidable shutter 224 has been moved aside along associated rails 226.

The slide preparation enclosure 204 is provided with a microscope eyepiece opening 228 which is likewise fitted with a bellows device similar to the one (218) just described above, for engaging around the movable eyepieces (86) of the microscope (84) disposed in that enclosure and provided for enabling the selected elements to be treated and made up into slides.

That slide preparation enclosure 204 is provided with a frontal access opening 230 through which the operative's hands may be inserted directly so as to manipulate objects within that enclosure without the use of sealed-in gloves. That access opening is normally closed by a vertical transparent curtain 232 which is made up, as in the case described earlier, of a plurality of vertically handing transparent strips 234 disposed side by side in overlapping relationship.

A second examination enclosure 236 similar to the first-mentioned examination enclosure 202 may be mounted alongside the enclosure 202 in backto-back relationship therewith, so that examination of different samples of asbestos materials (or of other toxic or dangerous materials, e.g. pathogens) may be carried on simultaneously. That second examination enclosure 236 may be connected by connecting ducts 238, 240 with the respective sample preparation and slide preparation enclosures 200 and 204, such ducts being normally closed off by normally-closed sliding doors (not shown).

Claims (35)

1. A toxic-specimen examination enclosure comprising: (i) a closed envelopewhich defines within itself an examination chamber, and which incorporates -- at least one normally-closed port means through which toxic specimens may be introduced into and/or expelled from said chamber, at least one operative's flexible glove extending through and secured in a gastight manner in an aperture formed in the envelope, for enabling objects within said chamber to be manipulated by an operative outside the enclosure, and - at least a portion thereof that is yieldable relative to the other parts of said envelope; and (ii) a microscope disposed within said chamber and having at least one eyepiece that is movable relative to a stationary specimen platform of the microscope for adjusting the focus of the microscope, which eyepiece extends through and is secured in a gas-tight manner in an aperture formed in said yieldable portion of said envelope, so that said eyepiece and the adjoining parts of said yieldable portion move together when the focus of said microscope is being adjusted, said yieldable portion providing freedom of movement of said eyepiece for adjusting said focus.

2. An enclosure according to claim 1, wherein said microscope is a stereoscopic microscope having two transversely spaced eyepieces, and each said eyepiece extends through and is secured in a respective aperture formed in said yieldable portion of said envelope.

3. An enclosure according to claim 1 or 2, wherein said yieldable portion includes a bellows sealed at one end thereof to said other parts of said envelope, and an end closure member sealed to the opposite end of said bellows and having said aperture or apertures formed therein for receiving said eyepiece or eyepieces respectively.

4. An enclosure according to any preceding claim, wherein said yieldable portion of said envelope is transparent.

5. An enclosure according to any one of the claims 1 to 3, wherein said envelope is transparent.

6. An enclosure according to any preceding claim, wherein said envelope also incorporates a connection pipe for enabling connection of said examination chamber with a gas exhausting means, whereby a small negative pressure can be maintained therein relative to an atmosphere outside that chamber.

7. An enclosure according to claim 6, wherein said envelope also incorporates a filter secured in a gas inlet port formed in said envelope.

8. An enclosure according to any preceding claim, wherein said port means includes normallyclosed inlet and outlet ports formed in said envelope at positions disposed respectively on opposite sides of said microscope, for enabling toxic specimens to be moved on to said microscope specimen platform from one side thereof and to be removed therefrom on the opposite side thereof.

9. An enclosure according to any preceding claim, wherein said envelope incorporates at least one other operative's flexible glove, secured in like manner to said at least one glove at a position spaced from said at least one glove.

10. An enclosure according to any preceding claim, in combination with a sample-preparation enclosure which comprises a closed envelope which defines within itself a sample-preparation chamber, and which incorporates -- a normallyclosed inlet port means through which a closed package of a specimen material may be introduced into that preparation chamber, - a normally-closed outlet duct which communicates with said examination chamber via said port means incorporated in said envelope defining that chamber, and - a transparent viewing portion through which an operative may view operations carried on within said sample-preparation chamber.

11. An enclosure according to claim 10, wherein said envelope defining said sample-preparation chamber incorporates a normally-closed refuse exit port through which sample material surplus to that required for a representative specimen for examination in said examination chamber may be expelled to a refuse collection bag.

12. An enclosure according to claim 10 or 11, wherein said envelope defining said sample preparation chamber incorporates a normally-closed sample exit port which communicates with a movable decontamination vessel into which a packaged sample exiting via said sample exit port may fall so as to be decontaminated by a decontamination liquid when provided in said vessel.

13. An enclosure according to claim 12, wherein said decontamination vessel is slidable on rails secured on said sample preparation envelope.

14. An enclosure according to any one of the claims 10 to 13, wherein said envelope defining said sample preparation chamber incorporates a connection pipe for enabling connection of said sample preparation chamber with a gas exhausting means, whereby a small negative pressure can be maintained in said sample preparation chamber relative to an atmosphere outside that chamber.

15. An enclosure according to any preceding claim, in combination with a post-examination enclosure which comprises a closed envelope, which envelope defines a post-examination chamber, and which incorporates -- a normally-closed inlet duct which communicates with said examination chamber via said port means incorporated in said envelope defining that chamber, - an access means for enabling an operative's hands to manipulate objects disposed within said post-examination chamber, - a transparent viewing portion through which can operative may view operations being carried on within said post-examination chamber.

16. An enclosure according to claim 15, wherein said transparent viewing means comprises a magnifying means.

17. An enclosure according to claim 15, wherein said envelope defining said post-examination chamber includes at least a portion thereof that is yieldable relative to other parts of that envelope, and including within said post-examination chamber a microscope having at least one eyepiece that is movable relative to a stationary specimen platform of the microscope for adjusting the focus of the microscope, which eyepiece extends through and is secured in a gas-tight manner in an aperture formed in said yieldable portion of said envelope defining said post-examination chamber.

18. An enclosure according to claim 17, wherein said microscope disposed in said post-examination chamber is a stereoscopic microscope having two transversely spaced eyepieces, and each said eyepiece extends through and is secured in a gas-tight manner in a respective aperture formed in said. yieldable portion of said envelope defining that chamber.

19. An enclosure according to claim 17 or 18, wherein said yieldable portion includes a bellows sealed at one end thereof to said other parts of said envelope defining said post-examination chamber, and an end closure member sealed to the opposite end of said bellows and having said aperture or apertures formed therein for receiving said eyepiece of eyepieces respectively.

20. An enclosure according to any one of the claims 17 to 19, wherein said yieldable portion of said envelope defining said post-examination chamber is transparent.

21. An enclosure according to any one of the claims 17 to 19, wherein said envelope defining said post-examination chamber is transparent.

22. An enclosure according to any one of the claims 15 to 21, wherein said envelope defining said post-examination chamber also incorporates a connection pipe for enabling connection of said post-examination chamber with a gas exhausting means, whereby a small negative pressure can be maintained in said post-examination chamber relative to an atmosphere outside that chamber.

23. An enclosure according to any one of the claims 15 to 22, wherein said access means comprises a vertical curtain hanging in a sealing manner across an access aperture formed in the envelope defining said post-examination chamber, which curtain comprises a plurality of vertically dependent strips of a soft, flexible material having in overlapping relationship.

24. An enclosure according to any preceding claim, wherein the or each said envelope defining a respective chamber comprises a flexible impervious sheet material, which material is supported on a rigid shape-defining framework.

25. An enclosure according to claim 24, wherein the or each said rigid framework comprises two similar end frames which are spaced apart by parallel, longitudinal spacer members.

26. An enclosure according to claim 25, wherein in the or each said envelope said end frames are disposed outside the envelope, and said longitudinal spacer members pass through chamber defined by the envelope, said envelope being secured to said end frames by loops attached to said envelope.

27. An enclosure according to any one of the claims 1 to 23, wherein the or each said envelope defining a respective chamber comprises a rigid impervious sheet material.

28. An enclosure according to claim 27, wherein said rigid sheet material comprises a transparent plastics material.

29. An enclosure according to claim 15, as dependent of the claim 10, wherein there is provided a second examination enclosure which is similar to the first-mention examination enclosure, and which is connected to said sample-preparation and postexamination enclosures respectively in like manner as the first-mentioned examination enclosure.

30. A method of examining a toxic-specimen by means of an examination enclosure according to any one of the claims 1 to 9, including the steps of -- introducing such a specimen into an examination enclosure as defined in any one of the claims 1 to 9 via said port means, - placing said specimen on the specimen platform of said microscope, - adjusting the focus of said microscope and observing the specimen through said microscope, and - subsequently expelling said specimen via said port means.

31. A method of examining a toxic-specimen using an apparatus as defined in any one of the claims 10 to 14, including the steps of -- introducing a packaged sample of a toxic material into said sample preparation enclosure, - opening said packaged sample and visually selecting a representative specimen of that material, - placing that specimen in a vessel and passing that vessel through said port means into said examination chamber, - placing the representative specimen or a part thereof on the specimen platform of the microscope, and examining it through the or both microscope eyepieces, - selecting part of said specimen and incorporating it a microscope slide, expelling said slide through said port means for further examination outside the examination enclosure, - returning the unused parts of the representative specimen to said sample preparation enclosure and repacking it there either as a sample to be kept for record purposes, or as refuse to be disposed of, and - finally expelling the packaged material from said sample preparation enclosure.

32. A method according to claim 31, modified for use in an apparatus as defined in any one of the claims 15 to 23, in that after selection in said examination chamber of material for incorporation in a microscope slide, the selected material is conveyed in a vessel into said post-examination enclosure where it is incorporated into a microscope slide by the direct manipulation of that selected material by the hands of an operative without the use of built-in gloves.

33. A method according to any one of the claims 30 to 32, substantially as hereinbefore described with reference to and as illustrated by any single figure or group of associated figures of the accompanying diagrammatic drawings.

34. An apparatus according to any one of the claims 1 to 29, substantially as hereinbefore described with reference to and as illustrated by any single figure or group of associated figures of the accompanying diagrammatic drawings.

35. Any and every aspect and/or combination of the features of the present disclosure, not otherwise specifically claimed in the preceding claims.