Patent Publication Number: US-2009222984-A1

Title: Decontamination unit

Description:
This invention relates to a portable decontamination unit in which individuals can be decontaminated following an emergency incident. 
     Decontamination of individuals is needed when they have become contaminated with dangerous materials (such as nuclear, biological or chemical materials). This usually occurs as a result of an accident, and thereafter decontamination is needed as an emergency measure. Decontamination is usually achieved by simply washing the casualties using a shower or similar apparatus, usually with the addition of soap or detergent, within a room or shelter of some type made specifically for this purpose. 
     The specifications needed for a decontamination facility depends on the needs of those who require decontamination. If those who require decontamination are ambulatory and able to decontaminate themselves (usually a process similar to having a normal shower), they do not require assistance from those operating, or “staffing”, the facility. However, if those who require decontamination require assistance during the decontamination process (including undressing and dressing) from those operating the facility, for example because of injury or illness caused by the contaminants, then the facility must be provided such that this is made possible. In particular some casualties may require urgent medical intervention to save life while at the same time being decontaminated, a process taught and practised by many authoritative bodies such as the British Army Royal Army Medical Corps. Where assistance is needed, space and access must be provided, for example a large enough washing area to accommodate both a stretcher and those assisting, and provision must be made for stretcher access through doorways. The invention focuses mainly on those who require assistance. 
     Known decontamination units are of various designs but can generally be divided into fixed permanent facilities (such as a room or building) or portable decontamination units (such as wheel based units, collapsible units (i.e. as a tent or inflatable structure). 
     Disposal of effluent from a decontamination unit directly into the public drainage systems, or otherwise into the environment, is subject to strict regulations imposed by various Government bodies. 
     This is normally not a problem for fixed permanent decontamination units as they are usually provided with a large capacity (often subterranean) holding tank. With regard to the volume of these tanks, the usual intension is to provide a large enough tank capacity that would give the user a reasonable degree of confidence that the tank will be able to hold all of the effluent from all the casualties from a contamination incident which the facility may face in the future. If the tank is of insufficient volume to deal with all the casualties this could result in overflow of the effluent into the drainage system or environment, or into the casualty washing area, depending on the configuration of the system. However, as such fixed units are not particularly restricted by size it is possible to construct adequately sized permanent tanks for such a units needs. Following decontamination of the casualties from an incident, disposal of the effluent held in the tank is usually done by pumping it into a mobile tank and transporting it elsewhere for disposal. 
     However, installing a fixed site holding tank is often expensive and problematic, additionally such large fixed site holding tanks are not an option when one needs to decontaminate individuals in an emergency situation that has occurred away from a fixed decontamination unit site. As a result, portable decontamination units have developed a number of alternative ways of handling their effluent: releasing the effluent into the public drainage system; having an effluent processing system; or, having a remote containment system into which effluent is pumped or flows from the decontamination unit. 
     Releasing effluent into the public drainage system is often illegal and damaging to the environment and to the safety of the public. The time taken to ready a decontamination facility for use is critical in many emergency situations, so it is most desirable to minimise this time. Similarly it is most desirable to minimise the complexity and number of procedures, and the number of staff required, to prepare the facility for emergency use. Including processing systems and remote containment systems adds to the complexity of the unit, thereby increasing the set up time. Furthermore, portable decontamination units often have to be set up in areas of restricted space (i.e. a car park space), which may not provide any additional space for remote effluent containment systems. 
     It is, therefore, an object of the present invention to provide a portable decontamination unit that includes an effluent handling system that does not possess any of the disadvantages described above. 
     Accordingly, in a first aspect of the present invention there is provided a portable decontamination unit comprising an enclosure and an effluent holding tank, wherein the effluent holding tank is provided within the enclosure. 
     The term holding tank would be well understood by the person skilled in the art, but for the avoidance of doubt, the term relates to a tank that is capable of permanently retaining a volume of liquid (e.g. effluent). 
     The term enclosure should be understood in its context by the person skilled in the art. An enclosure is preferably capable of separating an individual standing therein from the ground on which the unit rests and from view of individuals outside of the enclosure (in order to protect the modesty of those being decontaminated). The enclosure is preferably capable of retaining within the enclosure liquid that is released within the enclosure (e.g. effluent washed from the individual being decontaminated). Therefore, suitable enclosures include a base with side walls that enclose a central space, and optionally have a roof. 
     The term portable should be understood in its context by the person skilled in the art. A decontamination unit is portable if it is capable of being transported or conveyed from one position to another, i.e. it is not a permanent facility. 
     Such portable decontamination units have the advantage that they can easily be placed, ready for action, at the site of an emergency situation without the need to set up remote effluent holding tanks or prepare effluent processing systems. Additionally, units according to the present invention are able to contain effluent produced by washing contaminated individuals within the same space as is taken up by the enclosure in which the individuals are washed, which is desirable when only limited space is available. 
     In one embodiment of the present invention the portable decontamination unit further comprising a support surface provided above the base of the enclosure for supporting one or more subjects located within the enclosure. Preferably the effluent holding tank is provided below the support surface. Thus, the effluent holding tank may form the base of the unit. A first drain means may be included that permits drainage of effluent from the support surface to the effluent holding tank. This arrangement allows effluent to flow under gravity directly from the washing area (above the support surface) into the effluent holding tank. 
     The above described construction means that an individual standing within an enclosure would not stand in effluent. The individual would stand on a support surface from which effluent drains to the effluent holding tank. Such separation of individuals from the effluent is particularly desirable where the contaminant floats on the surface of the effluent water. Furthermore some contaminants, such as volatile liquids, can evaporate from the surface of the effluent, and if the casualties are not protected from this then unnecessary exposure to the vapour or gas can result. In order to prevent effluent and gases flowing from the effluent holding tank to the support surface the drain means may comprise a non-return valve. Also, optionally, the effluent holding tank has one or more venting port located on the outside of the tank near the upper edge (in order for the venting port to be located above the surface of the effluent), such that any vapour or gas within the effluent tank can escape to the outside of the enclosure (and not into the inside of the enclosure). These vents are preferably provided with a non-return valve such that the flow of gas or vapour can only occur in an outward direction from the tank into the surrounding atmosphere. In the event of the effluent holding tank becoming full, these venting ports could also function as overflow ports in the event of such an unplanned event, thus allowing effluent to escape from the tank into the environment or a drain rather than to overflow into the washing area or other areas occupied by individuals. 
     Maximising the volume (i.e. capacity) of the effluent holding tank is important. The number of individuals which can be decontaminated in a portable decontamination unit is limited by the volume of the effluent holding tank. A small capacity will severely limit the number of individuals which can be decontaminated, to a degree where the shelter has limited utility, and limit the degree to which the shelter can be relied upon to deal with all of the individuals which may present as a result of a contamination incident. 
     It has been found that one can maximise the volume of the effluent holding tank by using as much of the surface area of the base as possible to position the effluent holding tank. Preferably, the effluent holding tank extends over at least 50, 60, 70, 80 or 90% of the surface area of the base of the enclosure. Most preferably the effluent holding tank extends substantially over the entire base of the enclosure. 
     The volume of the effluent holding tank would preferably be more than 1 cubic meter and most preferably from 4 to 8 cubic meters. This could be provided, for example, with an effluent holding tank for the washing enclosure with optional dimensions as follows, approximately: 4 m by 2.5 m by 0.5 m high (+/−20%). If the volume of water used to decontaminate one casualty was taken as approximately 100 litres, this example tank (of 5 cubic meters, equalling 5000 litres) would provide enough capacity to hold the effluent from approximately 50 casualties. 
     In a preferred embodiment the effluent holding tanks are lead lined, a feature that is particularly advantageous when the effluent contains radioactive substances. 
     Individuals may be decontaminated using hand held showers that they themselves direct, or may be directed by emergency personnel. Alternatively, or in addition, the portable decontamination unit would further comprise a shower means for directing the flow of a decontamination liquid onto one or more subjects located within the enclosure. The shower means may be fixed to a side wall or ceiling of an enclosure prepared for washing. 
     Decontamination liquid which is normally showered onto the individual may include water, soap, detergent, bleack, and/or chelating agents, or similar fluids. The decontamination liquid may be provided to the shower means at the scene by being plumbed in from an external supply or by installing a remote decontamination liquid holding tank at the scene of the emergency. However, in order to improve the ability for the portable decontamination unit to be ready to operate as fast and efficiently as possible, the unit may further comprise a liquid holding tank. A conduit may be connected between the shower means and the decontamination fluid holding tank through which decontamination liquid retained in the decontamination liquid holding tank may flow to the shower means. When the decontamination liquid holding tank is located above the shower means the decontamination liquid may flow by gravity from the liquid holding tank to the shower means. Alternatively, or in addition, a decontamination liquid holding tank is provided below the support surface. In such an arrangement a pump (manual or powered) may be required in order to drive the decontamination liquid to the shower means. 
     In a particular preferred embodiment the decontamination liquid holding tank is provided as a bladder within the effluent holding tank. The advantage of such an arrangement is that the unit may be delivered to the site of an emergency ready for use. The effluent holding tank would be filled with a bladder which in turn would be filled with decontamination liquid. As the decontamination liquid is driven from the bladder to the shower means to decontaminate an individual, space is created in the effluent holding tank as the bladder shrinks, that space in turn is filled by effluent produced by the decontamination procedure. 
     Alternatively, the effluent holding tank is provided as a bladder within the decontamination liquid holding tank. In this instance the drain means communicates with the bladder effluent holding tank. 
     Bladders may be made of any flexible material, preferably one that is capable of acting as a physical barrier to liquids (particularly effluent). For example, the bladder may be made of a flexible plastics. 
     In order to prevent discomfort for the individuals the enclosures are of sufficient height to accommodate a standing human adult therein. 
     In some emergency situations a number of individuals may be required to be decontaminated simultaneously, and for modesty require separate enclosures. In addition to showering, further actions like dressing, undressing, carrying out medical treatments may be required to take place within the portable decontamination unit. Preferably, each action should be undertaken in a separate enclosure, however, often washing and medical interventions will be undertaken in the same enclosure. 
     Thus, in a further embodiment of the present invention, there is provided a at least one further enclosure, wherein the enclosures are arranged so that a side wall of an enclosure abuts with a side wall of an adjacent enclosure thereby forming a modular portable decontamination unit. 
     One or more enclosure may be for one or more subject to disrobe within that enclosure. One or more enclosure may be for one or more subject to wash contaminants from their body within that enclosure (preferably such an enclosure comprises a shower means). One or more enclosure may be for one or more subject to put on clothes within that enclosure. 
     With the above described modular system, the enclosures can be connected together to form a portable decontamination unit in a wide range of shapes, sizes and different enclosure combinations. For example, the enclosures may be arranged to abut each other in a row so as to form a linear modular portable decontamination unit (e.g. disrobing enclosure then washing enclosure then an enclosure for putting on clothes in). At least one enclosure can be arranged so that two or more adjacent walls of that enclosure abut with adjacent enclosures so as to form a non-linear modular portable decontamination unit (e.g. four square or rectangular based enclosures may be arranged so that one corner of each enclosure abuts at a common point so as to form a substantially cube shaped unit). Furthermore, enclosures can be arranged to form a combination of a linear and a non-linear modular portable decontamination unit. 
     In order to retain the chosen confirmation of enclosures the unit may further comprise releasable connecting means provided on one or both abutting enclosures for securing the abutting enclosures together. These releasable connecting means can optionally be any appropriate fitting known to the person skilled in the art, for example, male and female couplings (such as eye and hooks, bolts and screws, Velcro), brackets, magnets, springs, zips catches and/or clasps. When a male and female coupling is used, one half of the partnership may be located on a first enclosure and the other located on the second enclosure, which is arranged to abut with the first enclosure. 
     Gaps which may be present between enclosures after assembly of the unit by joining together various enclosures are not undesirable as this may help provide ventilation of the enclosures. 
     Furthermore, since the undressing and dressing enclosures (e.g. ancillary enclosures) are preferably provided such that they are similar or identical to each other, their roles can be interchanged, thus simplifying manufacture, supply, etc. Furthermore this enables the user, or operator, of the shelter to easily change the use, or role, of an ancillary enclosure to suit requirements. Even on the day of an emergency decontamination, the individual can make a decision on the role of an ancillary enclosure: for dressing or undressing or indeed any other role, based on the requirements presenting themselves on the day. For example individuals may unexpectedly present themselves to the unit dressed in clothing which is complex and time consuming to remove (for example personnel from a factory wearing protective clothing), in this event the operator may elect, on the day, to use two of the ancillary enclosures for undressing and one for dressing. 
     The user can choose to use any combination of the different available enclosures provided to form a decontamination unit. For example, the user could choose to use one washing enclosure, two undressing enclosures and two dressing enclosures, joined together. The invention also optionally provides for the washing enclosure to be used independently without any of the ancillary enclosures, if required by the user, by means of curtains or other barrier system, such as a fixed partition, within the washing enclosure to provide small undressing and dressing areas within the washing enclosure. The curtain rails are optionally fitted in the washing enclosure to provide for this option should the user wish to use it. 
     By electing to install openings between enclosures in strategic places (for example by means of using interchangeable side walls that include doors, omitting side walls, or cutting holes in side walls) the user can pre-plan such a flexible use of enclosures as described above. Thus, an opening may be provided in one or more abutting side walls of enclosures for enabling a subject to pass from one enclosure through the opening to the adjacent enclosure. 
     In order to further maximise the capacity for storing effluent the effluent holding tanks of two or more enclosures may be joined to enable flow of effluent between the tanks, or may form a single effluent tank. The join may be made using a conduit through which effluent may pass between tanks. It should, however, be understood that not all enclosures in a modular decontamination unit have to comprise an effluent tank. The flow of effluent between effluent holding tanks is preferably urged by gravity, although pumps may be included. It has been found that the capacity of the effluent holding tanks built into the base of a completed  3  enclosure unit provides a reasonable degree of confidence that the tank will be able to hold all of the effluent from all the casualties from a typical contamination incident, although further auxiliary tanks may be attached if necessary. 
     When arranging the enclosures into a modular decontamination unit interconnections between the enclosures are less able to obstruct the abutting of walls of adjacent enclosures, or (in the case of conduits) kink and become blocked, if the interconnections are made as short as possible. Thus, for example, the releasable connecting means and/or the portion of the conduit provided between the joint effluent tanks that exits the effluent tanks are located at one or more corner of the enclosures (each corner of a rectangular based enclosure having the potential to abut with the corners of 3 other enclosures). When the enclosures have a substantially rectangular base, the releasable connecting means and/or the portion of the conduit provided between the joint effluent tanks that exits the effluent tanks are preferably located towards each of the corners at the base of the enclosures. Most preferably the releasable connecting means and/or the portion of the conduit provided between the joint effluent tanks that exits the effluent tanks are located in a recessed blunt corner. 
     Often it is a car park that is the most suitable place to position a portable decontamination unit. Thus, the unit and/or enclosure is preferably sized and shaped so as to be accommodated within a car parking space. In order to maximise the capacity of the effluent holding tank, when this is relative to the surface area of the base of the unit, the unit and/or the enclosures are preferably sized and shaped so as be of substantially similar size and shape as a car park space, or multiple car park spaces. Most preferably, a washing enclosure is sized and shaped to fit into a standard car park space, whilst the undressing and dressing enclosures are sized and shaped to fit into half of a car park space. Accordingly a unit comprised of the three different enclosures should fit within two adjacent car park spaces. For the avoidance of doubt and in the interest of clarity, but not wishing to be restricted further, a car park space is a space suitable for parking a single car, and is preferably about 4×2.5 m (+/−20%). 
     If electrical power and a water supply for the unit are required these are preferably taken from a nearby building. Lighting, and heating are preferably incorporated into the units for utility and comfort, and extractor fans are preferably provided to remove contaminated air from within the shelter. The extractor fans are optionally located on the ceiling of the enclosures, and thus the tendency of hot air to rise would add to the flow of air through the extractor fans. Preferably fan heaters are used to create positive pressure inside the enclosures, creating ventilation by means of air escaping through, for example, the doors, vents, gaps between enclosures, etc. The decontamination liquid used for washing casualties is preferably heated by use of the electrical power, preferably by means of commercially available domestic shower units, and with optionally four per washing enclosure. Alternatively, the units may be air sealed excepting an air outlet that incorporates filters to prevent the escape of harmful substances to the outside. 
     The conduits and, if external supplies are required, the decontamination fluid supply and effluent connection conduits to the unit are preferably provided with easily connected and disconnected fittings and preferably achieve this by use of commonly available garden hose fittings such as the HOZELOC® or GARDINA® brand hose fitting systems, these being widely available at garden centres. Also, these fittings are preferably provided with the feature that once disconnected, the flow of water or effluent is automatically stopped by means of a valve or similar apparatus, this being a feature found on many of these commonly available hose fitting systems. Use of this type of commonly available connections also has the advantage of being compatible with commonly available garden hose, which is also preferably used throughout the shelter system. These connections would allow easy connection and disconnection of the sections of hose used in the shelter system, if this was required by the user (i.e. those personnel staffing, or operating, the unit), before, during or after decontamination. 
     Furthermore the connections used in all of these parts of the unit are preferably provided such that they are all compatible with each other. Use of the above described simple and commonly available fittings and hose helps in enabling the user to easily adapt or repair or replace the hose and connections. 
     The fittings used would also be provided preferably at both ends of all of the conduits used, to allow detachment of both ends of the conduit, if required by the user. 
     These commonly available fittings used preferably throughout the unit, as described above, usually use a male and female fitting system. If a male and female fitting system is used, then preferably the pieces of conduit used to connect the various parts of the unit (for example for connecting remote effluent holding tanks to the effluent holding tanks in the base of the enclosures), are provided with either male of female fittings such that the connecting hose pieces are interchangeable between different areas of the shelter, as far as this is possible. For example if all of the conduits were to be fitted with male fittings at both ends, and all of the effluent tanks were to be fitted with female fittings, this would allow the hose pieces to be interchanged and either end of the conduit used to make the various effluent holding tank connections. Furthermore the fittings are preferably used such that an automatic close off feature described above is provided on the effluent holding tank side of the fitting, and also optionally on the conduit side of the fitting. 
     Alternatively, the connecting fittings for attachment to parts of the unit or external devices through which effluent is to flow is sized and/or shaped differently from those connecting fittings for attachement to parts of the unit or external devices through which decontamination fluid is to flow. Preferably, the fittings for attachment to parts of the unit or external devices through which effluent is to flow are fittings commonly used by waste contractors, and the connecting fittings for attachement to parts of the unit or external devices through which decontamination fluid are those used for garden hoses, such as HOZELOC®. 
     The conduit and connecting fittings used, in parts or the entire unit, are preferably made from materials such that, the conduits and fittings have a reduced tendency to absorb and or leak toxic or dangerous substances. 
     In order to facilitate an option of using the washing enclosures to decontaminate two parallel streams of ambulatory casualties, for example one male stream and one female stream, in certain layouts of the modular units the washing enclosure is preferably provided with a curtain rail, or a similar temporary partition, down the centre of the washing enclosure. 
     The effluent holding tanks preferably have drainage ports (preferably at or near one or more lower corner of the effluent tank). The drainage ports are also preferably provided in the aforementioned recesses, thus reducing the risk of accidental damage, and the corner location may also give better access to the ports, for example when two enclosures are attached together. 
     The invention also preferably provides that the side walls of the enclosures can be constructed to incorporate interchangeable panels, to allow a selection of different panels to be installed to suit the users needs. These panels are preferably provided with attachment fittings such that they can be easily removed and reattached by the user. These attachment fittings are optionally provided such that they also function as the releasable connecting means for attaching the enclosures together. These interchangeable panels are preferably provided as window panels, solid panels (alternatively described as or blank or plane panels) and/or door panels. The window panels optionally include a clear (non opaque) opening window. The door panels can optionally be provided in one or more different types, for example different door types for internal doors (for connecting between enclosures) and external doors. These interchangeable panels preferably enable the different enclosures to be attached together in the various different layouts possible, with door panels being fitted into the appropriate places where the enclosures attach together to facilitate casualty movement between enclosures by opening and closing the doors. Optionally the door panels connecting the enclosures can be provided such that the moving (hinging) actual door can be removed thus leaving a door shaped space between enclosures without any door to close the door shaped space, should the provider wish to use this as an option. 
     Hinged doors are preferably used but optionally other alternatives can be used in the openings between the enclosures, including curtains for example. An optional alternative, which can be used in the openings between the enclosures, is to omit interchangeable panels where the enclosures abut, leaving an opening between the enclosures. 
     Optionally the unit is constructed such that the effluent holding tanks are detachable from the other parts of the unit (e.g. the walls, roof, etc, or what could be termed the “superstructure” of the shelter). This could optionally be done such that detachment and reattachment could be carried out easily and reversibly by the user if needed. Such attachment of the superstructure of the shelter enclosures to the tanks could be made by a variety of means such as clips, pins, brackets, fasteners, clasps, bolts, springs, spring loaded clips or other fittings. Also the tanks forming the base could also optionally be provided with a lip or protuberances or recess or grooves or similar such that when the superstructure sits on, and fits onto, the tanks it engages with the features in optionally a male and female manner or similar. Optionally the enclosures can be provided with a detachable superstructure which has a floor or partial floor, provided such that it fits onto the top surface of the tank which forms the base of the unit. 
     Detachment of the superstructure of the enclosure from the tank forming the base of the shelter, as described above, may be a useful feature to enable the enclosure to be broken down into smaller parts as it may make moving, maintaining or cleaning the enclosure easier under some circumstances. Also this feature may aid emptying of the tanks built into the base of the unit, as it may be easier to tip up the tank if it was separated from the superstructure, allowing better flow of effluent through the drainage port. Additionally a detachable superstructure may also make removal of the effluent from the site easier in some circumstances as separation of the tank from the superstructure would make it easier for the tank to be removed from the site with the effluent contained within it. 
     Drainage of the effluent holding tanks is usually necessary after a training session where water has been allowed to flow into the tanks, or after decontamination of casualties. The invention provides that in the former the effluent could be drained into a nearby drain using a conduit attached (preferably using fittings as described) to the drainage port, but in the latter case the effluent would need to be transferred into another tank for removal and disposal (optionally using commonly available conduit fittings and conduits as described above to help facilitate this). 
     The invention also preferably provides for external auxiliary effluent holding tanks. These can be attached to one or more outside walls of, preferably, any of the enclosures when in their storage position. 
     These externally attached effluent tanks are preferably fitted with commonly available fittings such as conduits, as described above, to connect them to the effluent tanks built into the base of the enclosures. 
     Externally attached auxiliary effluent tanks can be moved to their deployed (operational) position, and or connected to an effluent flow, by the operator prior to, or during, casualty decontamination. This may be done in the event that the extra capacity of the tanks is required (for example if large numbers of casualties were requiring decontamination). Flow of effluent from the effluent holding tank within the enclosures to these auxiliary external effluent tanks, when in their operational position is preferably by gravitational flow, i.e. without the use of pumps. 
     Externally attached auxiliary tanks, if stored in a location such as nearby or on the roof of the shelter, can be attached (in terms of effluent flow) to the effluent tanks built into the base of the enclosures while in their storage location if required by the user, or can be attached before or during casualty decontamination. 
     With regard to the external auxiliary effluent holding tanks which are attached to one or more outside walls of the enclosures, these tanks are preferably placed on the ground beside the decontamination shelter in their deployed position, or optionally a longer conduit can be provided to allow placement of the tank on the ground further away from the shelter, and so flow may be driven by gravity. These tanks can be stored (stowed) on the sidewall of the shelter either within a housing provided for the purpose or not within a housing. The tank is preferably brought down to the deployed (operational) position by the operator, preferably using a simple and straightforward mechanism such as a removable pin, release chord, lever, or similar apparatus. When in the stowed position these tanks and or their hosing are preferably provided such that they do not obstruct or interfere with pedestrians, motor vehicles, etc which may pass close by the shelter. This can be achieved for example by ensuring that the tank storage position is high enough from the ground. When provided within a housing, these tanks are preferably collapsible or foldable, being optionally constructed of a flexible material such as flexible plastics sheeting, to further facilitate space saving in their stowed position. Alternatively these tanks can be constructed of rigid material in which case they are preferably not provided within housing. These tanks (or the housing within which they are stowed) are optionally attached to the side wall of the enclosure by means which is compatible with the releasable connecting means used to connect the enclosures together, and or the attachment points used to attach the interchangeable panels, as described above. 
     The above described system for auxiliary attached effluent tanks would preferably allow attachment (in terms of effluent flow) of several auxiliary tanks simultaneously to several drainage ports on the shelter as required by the user, and would also preferably allow attachment of one auxiliary tank after another to one enclosure drainage port, if required by the user. The latter may be desired if an auxiliary tank became full or damaged for example. The auxiliary effluent tanks may be provided in the form of collapsible pillows. 
     The invention also preferably incorporates hinged ramps, which fold up into their stowed position, the ramps being provided for the purpose of enabling wheeled casualty stretchers etc. to be brought in and out of the unit Stowing the ramps in this way provides for space saving, and enables rapid and simple deployment. The invention also preferably provides for these ramps to act as doors when in their stowed (up) position. Therefore when moved to their operational (down) position, the doorway would be opened as a ramp, allowing casualties to enter or exit. 
     The unit may further comprise an awning or fold out rigid structure capable of providing further cover for individuals and a place for emergency personnel to work. 
     The invention also preferably provides features incorporated specifically to enable that the unit can be used for other purposes, i.e. uses other than casualty decontamination, such as a staff smoking area. Switches, taps and other controls inside the unit are preferably made tamper proof, for example by providing protection in tamper proof boxes. Preferably some of the controls can be made accessible to those using the unit for other uses other than decontamination, such as access to lighting switches and limited heating controls, but optionally not to the water taps or shower controls. Also window panels are provided as described above in order to help facilitate these other uses, such as a staff smoking area, if required by the user. Seats and benches for sitting are also optionally incorporated within the unit, with preferably a spring folding mechanism which returns the seat or bench back to the vertical position after it has been used. The seats can then be used for example when in use as a smoking shelter, but fold out of the way when used for decontamination. 
     The invention also preferably provides for use of the shelter as a shower area, for routine washing of personnel (as opposed to removal of dangerous materials referred herein as “decontamination”) and provides features to enable this use, including for example drainage of the water used for showering. This could be achieved by preferably connecting one or more of the drainage ports to a conduit or conduits that passes to a public drain. If the shelter was then to be required for decontamination, then the aforementioned conduit would be disconnected by the user (or close off by means of a valve or tap or similar apparatus) such that escape of contaminated effluent did not discharge into the drain or otherwise into the environment. 
     With reference to the erection of the unit, uneven ground or ground with is not level should preferably be prepared for the shelter by making the ground level and even. Alternatively the unit can be supported on supports consisting of, for example, wooden batons or railway sleepers, or the unit itself to include adjustable legs to overcome the problems of unprepared ground. To enable use of the shelter on unprepared ground, the base should preferably have sufficient strength to withstand the forces and wear and tear that may be encountered. Furthermore, the releasable connecting means provided to attach the enclosures together should preferably make allowance for use of the shelter on unprepared ground, by means of, for example, providing a flexible joining mechanism such as springs with hooks attached, or by providing more than one bolt hole for attachment bolts. 
     The walls of the enclosure and unit are preferably rigid. Preferably the enclosures are ready constructed enclosures that need not be constructed on site. Thus, only the connecting of the enclosures, if required, to form a modular decontamination unit is required in order to make the unit ready for use. 
     The pumps that may be employed in the unit of the present invention may be manually operated pumps or motor driven pumps. Such pumps may be operable from outside the enclosure by, for example, a member of the emergency service if a pump handle is provided outside the enclosure, or inside by the individual if the pump handle is provided within the enclosure. 
     Many portable decontamination units are required to be erected at the scene of the emergency. Accordingly, they employ foldable, non-rigid walls. However, this means that there will be a delay in using the unit as it is constructed. 
     Thus, in a further aspect of the present invention, there is provide a rigid modular portable decontamination unit comprising a plurality of enclosures, wherein the enclosures are arranged so that a side wall of an enclosure abuts with a side wall of an adjacent enclosure. 
     Such structures preferably have ready constructed enclosures that need not be constructed on site. Thus, only the connecting of the enclosures, if required, to form a modular decontamination unit is required in order to make the unit ready for use. 
     Any features of the portable decontamination unit, enclosures and/or modular portable decontamination unit discussed in the first aspect of the present invention may be included in the further aspect of the present invention. 
    
    
     
       The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:— 
       Figure one shows a perspective view of the portable decontamination unit assembled using one of each of three types of enclosure, in a linear layout. 
       Figure two shows a plan view of the portable decontamination unit in a linear layout, as in  FIG. 1 . 
       Figure three shows a plan view of the portable decontamination unit, assembled using one of each of the three types of enclosures, in a non-linear or square layout. 
       Figure four shows a cross section through an enclosure used for washing. 
       Figure five shows a plan view of a portable decontamination unit that includes one washing enclosure and three ancillary enclosures. 
       Figure six shows a plan view of a portable decontamination unit that includes one washing enclosure and four ancillary enclosures. 
       Figure seven shows a perspective view of the portable decontamination unit including interchangeable panels. 
       Figure eight shows a perspective view of the portable decontamination unit including showing releasable connection means. 
       Figure nine shows a perspective view of the recessed blunt corner that incorporates inter alia the releasable connection means. 
       Figure ten shows a perspective view of the connections between of two effluent holding tanks in adjacent enclosures. The enclosures are shown pulled apart slightly to aid clarity of the connection. 
       Figure eleven shows a perspective view of an externally attached auxiliary effluent holding tank fitted to the sidewall of a enclosure. It is shown in its stowage position. 
       Figure twelve shows a perspective view of an externally attached auxiliary effluent holding tank, as in figure eleven, with the tank in its operational position. 
       Figure thirteen shows a perspective view of the portable decontamination unit with hinged ramps in the up and down positions. 
       Figure fourteen shows a perspective view of the portable decontamination unit including an external pump. 
       Figure fifteen shows a perspective view of a portion of the portable decontamination unit, focusing on the connections between adjacent effluent holding tanks and pump. 
       Figure sixteen shows a section through a portion of the portable decontamination unit in order to illustrate a pump arrangement. 
       Figure seventeen shows a section through a portion of the portable decontamination unit in order to illustrate a bladder in tank arrangement. 
     
    
    
     The portable decontamination unit, as illustrated in  FIG. 1  in perspective and in  FIG. 2  in plane, comprises three enclosures arranged in a linear layout. The middle enclosure ( 1 ) is sized so as to have a base surface area equal to that of a standard car parking space and may be suitable for use as an enclosure in which contaminated individuals are showered. The surface area of the base of the ancillary enclosures ( 2 ,  3 ), provided on either side of the middle enclosure is half the size of the middle enclosure. Effluent holding tanks ( 18 ) are provided in the base of each of the enclosures ( 1 ,  2 ,  3 ). A door panel ( 16 ) with an external door ( 6 ) is provided in the end wall of an ancillary enclosure ( 3 ) to permit individuals to enter or leave the unit. The side walls are provided with blank panels ( 15 ). 
       FIGS. 2 ,  3 ,  5  and  6  illustrate various layouts of a modular portable decontamination unit. Access for stretcher patients in and out of the shelter is preferably through external doors ( 6 ) as for walking patients for some layouts where the enclosures are aligned such that stretcher access is possible through the doors, as in  FIG. 2 . However, for other layouts, where the enclosures are not aligned in a way that allows the stretchers to pass through the sequential doors, such as in  FIG. 3 , stretcher access is optionally through additional external doors ( 7 ), thus by passing the dressing ( 2 ) and the undressing ( 3 ) enclosures. The need for these additional stretcher access doors would depend on the exact layout of the shelter, stretcher size and user preference. In  FIG. 5  the enclosure  1  is used as washing enclosure, whilst enclosure  2  can be a changing enclosure and enclosure  3  a dressing enclosure. Additional enclosure  12  can be an additional dressing enclosure or changing enclosure, depending on the needs of the incident. In order to facilitate an option of using the washing enclosure to decontaminate two parallel streams of ambulatory casualties, for example one male stream and one female stream,  FIG. 6  shows a washing enclosure ( 1 ) curtain rail ( 13 ), to enable quick installation of a temporary partition down the centre of the washing enclosure. 
     The layout shown in  FIG. 2  would occupy two car parking spaces end to end, and in the example layout in  FIG. 3 , the unit would occupy two car parking spaces side by side, and in the example layout shown in  FIG. 6  the unit would occupy three parking spaces side by side. This allows efficient use available of space which may be an issue in some locations such as hospital Accident and Emergency Departments where car parking spaces are usually available near the entrance. 
       FIG. 4  illustrates a cross section through an enclosure used for washing that does not require ancillary enclosures to be attached. The enclosure is divided by curtains ( 8 ) hung from rails ( 11 ), so as to define a small undressing area ( 9 ) and dressing area ( 10 ) within the washing enclosure. A shower head ( 4 ) is provided in the ceiling of the enclosure and a drain ( 5 ) between platform on which the individuals would stand and the effluent holding tank ( 18 ). The drain includes a non-return valve ( 19 ). 
     Interchangeable panels for use in the portable decontamination unit are illustrated in  FIG. 7 . These panels are provided with attachment fittings such that they can be easily removed and reattached by the user. These interchangeable panels are window panels ( 14 ), solid panels ( 15 ) (alternatively described as or blank or plane panels) and door panels ( 16 ). The window panels include a clear (non opaque) opening window. 
     Interconnections between adjacent enclosures are illustrated in  FIGS. 8 ,  9  and  10 .  FIG. 8  shows the releasable connecting means ( 17 ) formed from hooks and eyes, provided on the walls of the enclosure, for connecting the enclosure to adjacent enclosures. Also shown are the conduits ( 21 ) that exit the effluent holding tanks provided in recessed blunt corners provided at each lower corner of the unit.  FIG. 9  shows this feature in more detail, as well as showing a venting port ( 20 ) provided at in the upper portion of the effluent holding tank ( 18 ).  FIG. 10  illustrates how the effluent holding tanks in adjacent enclosures may be connected via a conduit in the form of a hose. The hose is attached to the effluent holding tank by a HOZELOC® fitting. 
       FIGS. 11 and 12  illustrate a auxiliary external effluent holding tank ( 23 ) and the housing ( 24 ) that attaches the tank to the upper portion of a side wall of the enclosure. A pin and catch mechanism ( 25 ) retains the housing ( 24 ) in a closed position around the stowed effluent holding tank ( 23 ) (see  FIG. 1 ). When the pin is released from the catch ( 25 ) the housing opens enabling the effluent holding tank ( 23 ) to drop to the floor (see  FIG. 12 ). 
       FIG. 13  illustrates an enclosure that includes two hinged ramps ( 26 , 27 ). When folded up into the stowed position, the ramp ( 27 ) forms a closure in the wall of the enclosure and enables the enclosure to be more suitable for transportation. When folded down into the operational position, the ramp ( 26 ) is provided for the purpose of enabling wheeled casualty stretchers etc. to be brought in and out of the shelter. 
       FIG. 13  illustrates portable decontamination unit that includes an enclosure for showering ( 1 ) and an ancillary enclosure ( 2 ) for dressing or undressing. Both enclosures ( 1 , 2 ) include an effluent holding tank ( 18 ) located in the base of the enclosures ( 1 , 2 ). The volume of the tank in the base of enclosure ( 1 ) is greater than the volume of the tank in the base of enclosure ( 2 ), in order to ensure that decontamination fluid pumped from the tank in enclosure ( 2 ) cannot exceed the holding capacity of the other tank. 
     A conduit ( 21 ) in the form of a hose is attached to the tank within enclosure ( 2 ) and is long enough to plumb into the shower means ( 28 ) and also the tank within enclosure ( 1 ). Therefore, the enclosures can be supplied to the scene of the emergency with the tank in enclosure ( 2 ) filled with decontamination fluid and connected to the shower means ( 28 ) via the conduit ( 21 ). Once the decontamination fluid is used up, and if the effluent holding tank in enclosure ( 1 ) is becoming full, the conduit ( 21 ) can be removed from the shower means ( 28 ) and instead connected to the tank of enclosure ( 1 ), thereby permitting a larger capacity for effluent. 
     The shower means may be supplied with decontamination liquid via a pump ( 29 ) or if external water pressure is available directly via a conduit ( 30 ). The pump ( 29 ) is manually operated by pumping a handle ( 35 ). A one way valve ( 31 ) is preferably provided to ensure that externally supplied decontamination liquid can flow to the shower but decontamination liquid pumped from the pump ( 29 ) can not flow out of the conduit ( 30 ). Similarly a one way valve ( 32 ) is preferably provided to ensure that washing water pumped from the pump ( 29 ) can flow to the shower, but adequately pressurised externally supplied washing water cannot flow into the pump ( 29 ). 
     A header tank ( 33 ), shown in  FIG. 14  and in more detail in  FIG. 16  includes an air release valve mechanism ( 34 ) to allow the escape of air out of the top of the header tank ( 33 ). The air release valve mechanism ( 34 ) is provided with a float such that when the liquid level in the header tank reaches or approaches the top of the tank, the valve is closed, thus preventing the escape of liquid from the top of the tank ( 33 ). 
       FIG. 17  illustrates the detail of an effluent holding tank that contains a bladder ( 36 ) for accommodating decontamination fluid. Two different types of connection fittings are shown on the side wall of this effluent tank: a first fitting ( 37 ) for connecting to the bladder ( 36 ) and second fitting ( 38 ) for the effluent holding tank ( 18 ). First fitting ( 37 ) may be used to connect the bladder ( 36 ) to the shower pump ( 29 ) or to other tanks or bladders containing decontamination fluid within the portable decontamination unit, using a pipe or hose ( 21 ). The hose ( 21 ) for transmitting decontamination fluid is provided with fittings ( 39 ) which are compatible with the fitting provided elsewhere in the shelter for decontamination fluid. The second fitting ( 38 ) is used to connect the effluent tank ( 18 ) to other effluent tanks in the unit, or to pipes or hoses leading to external disposal sites such as a tank or tanker truck. The hose for transmitting effluent is provided with fittings ( 40 ) compatible with the fittings provided elsewhere in the unit for effluent but not for the fittings provided for washing water, such as fittings ( 37 , 39 ). 
     In the event that an adequate supply of external washing water is available, the unit operator can elect to empty the bladder ( 36 ) (for example into the environment) in order to make space within the tank for effluent. This could be done for example by simply attaching a hose to the fitting accessing the decontamination fluid filled bladder. Alternatively, the unit operator could elect to decontamination fluid from the bladder with the effluent, by simply attaching the bladder to the shower pump ( 29 ) and pumping some of the decontamination fluid to the shower and hence into the drain and then the effluent tank. This may be advantageous in order to mix neutralising substances with the effluent.