Patent Publication Number: US-7217186-B2

Title: Mobile aeraulic isolation device against airborne contamination with variable geometry air diffuser

Description:
TECHNICAL FIELD 
   The invention comes within the technological sphere of ventilation devices fitted with an airflow diffuser to protect a sensitive zone against the entry of outside contamination. It concerns devices for decontaminating a gaseous fluid, of aerological isolating type, that is to say intended to deliver a flow of decontaminated air or to extract a flow of contaminated air, within a spatial part of a room. The invention specifically relates to the technological area of aerological isolating devices:
         comprising a mobile supporting chassis enabling global movement of the device (in moving position) relative to a bearer surface, the floor in particular, and an air diffuser (or air diffusion chamber),   having a multi-block air diffusion chamber of variable geometry, that is to say containing at least two rigid air-diffusing plenums (diffusing parts), mechanically connected to one another so that they are mobile relative to each other,   and fitted with complementary means for relative movement (in fixed in-use position) of at least one plenum of the air diffusion chamber relative to the other plenum and/or chassis.       

   The ambient air of premises is permanently contaminated by microorganisms derived from persons or the environment (bacteria, viruses, yeasts, moulds, . . . ). The human body is therefore surrounded by a considerable number of micro-organisms. The germs in the air have twofold origin: environmental and human. 
   Aerological biocontaminating vectors of human origin contain rhino-pharyngeal droplets, called Pflügge droplets (emitted when speaking, coughing or sneezing) of a diameter generally lying between 5 and 100 microns. As and when they settle, these droplets lose their water content, reducing their diameter down to as far as 0.5 microns forming droplet nuclei. These are all the more dangerous as they are concentrated in germs, they remain in suspension in air for a long time and may enter the respiratory tracts. In a hospital environment, airborne flora of human origin also contains bacteria from cutaneous and possibly digestive commensal flora of the surgical team, medical team and patients. 
   Environmental aerological biocontaminating vectors especially contain particles of dust or fabric coated with microorganisms. Airborne flora of outside air is mostly made up of  bacilli, micrococci, staphylococci . Gram negative  bacilli  and anaerobic bacteria are also found. Yeasts and fungi also belong to this environmental flora (e.g.  aspergillus fumigatus  . . . ). Finally, contaminated liquid particles are found in air caused by disturbance of contaminated water media ( Legionellosis  . . . ). 
   In the air, the lifetime of bacteria is sufficiently long for them to be considered as potential infection agents. Being a vector of intra-hospital contamination, air disperses particles carrying microorganisms over greater or lesser distances and insidiously promotes gradual contamination of the hospital environment. Several factors contribute towards the development of microorganisms in hospitals—firstly modern air treatment technologies (air conditioning) which, despite their beneficial effects, also set up dangerous germ reservoirs in piping, and secondly the increasing use of antibiotics, antiseptics and disinfectants which has led to the selection of increasingly resistant germs. At the same time, medical techniques have been developed in hospitals that are more and more advanced but also more aggressive for patients, while these patients have become more immunocompromised and therefore with high risk of infection. This accounts for the increasing occurrence of nosocomial infections caused by germs in the hospital environment (which usually have little intrinsic virulence) affecting patients with reduced resistance. 
   At the international conference on nosocomial infections in 1970, Brachman estimated that 10 to 20% of endemic nosocomial infections are airborne. 
   Some of these microroganisms colonise patients&#39; respiratory tracts and may, in weaker patients, be the cause of respiratory nosocomial infection. 
   In addition, to protect patients with low resistance to infection, the use of invasive procedures (that is to say investigation procedures or treatment which enters the skin, mucosa or a natural cavity of the body) can only be considered in a controlled microbial aerological environment. 
   The prevention of nosocomial diseases in hospitals requires breaking the chain of transmission of infectious agents, in particular the chain of airborne contamination. 
   To achieve this, a distinction is made between protective septic isolation intended to prevent a patient carrying a bacterial or viral infection, or who is colonised by a germ, from diffusing this infection. This is the case in particular for patients suffering or suspected to be suffering from contagious respiratory infections such as tuberculosis. On the other hand, a patient at risk is likely to be infected by the environment, by other patients, or by visits. Such patients must be given aseptic protective isolation. This type of case is normally found in burns units, haematology, oncology or transplantation departments. This particularly concerns patients who are immunocompromised through illness, neutropaenia treatment or suffering from medullary aplasia. The purpose of aseptic protective isolation is to avoid contact between a person and a pathogenic agent. These microorganisms may always be pathogenic ( tuberculosis bacillus  . . . ) or potentially pathogenic when they contaminate persons with reduced immune response ( pyocyanic bacillus, aspergillus , . . . ). It sets out to protect immunocompromised patients against all contamination of environmental or human origin (environment, staff, other patients, visitors . . . ). 
   Traditionally, the decontamination of airborne microorganisms around a sensitive area by means of ventilation is made:
     either globally inside the entire room, so-called “clean room” or “isolation room”,   or within a reduced delimited area, so-called “isolation area” inside a larger room.   

   A distinction is made between two types of clean or isolation rooms in the hospital sector:
     septic (infectious) isolation rooms which are generally maintained under negative pressure relative to adjacent premises, to prevent the exfiltration of infectious microorganisms derived from a patient in the room,   protective isolation rooms or aseptic isolation rooms which are generally maintained under positive pressure relative to adjacent premises, to avoid the infiltration of infectious organisms and to protect a susceptible patient in the room.   

   The invention concerns isolators both under positive pressure for aseptic isolation and under negative pressure for septic isolation. 
   Isolators or “bubbles” placed inside a room are generally made up of an envelope which surrounds:
     either an infectious patient, for septic isolators   or a susceptible patient, for aseptic isolators (or soft wall clean room).   

   The conventional decontamination method consists of causing a very large quantity of air to enter the isolation room, or the effective volume of the isolator. The effect of adding of this quantity of air is:
     either to dilute the contaminated air before it is expelled towards the outside, in turbulent or “non-unidirectional” systems,   or to ensure a “piston effect” repelling the contamination towards the outside, in laminar flow or “unidirectional” systems.   

   The air is filtered upstream from the flow in aseptic rooms or isolators, and downstream from the flow in septic rooms or isolators. 
   DESCRIPTION OF PRIOR ART  
   It is frequent practice for local air treatment to use an isolating device comprising a diffuser with variable geometry. 
   In the remainder of the description, the following equivalent terms will be used indifferently: diffuser or air diffusion chamber. Also the following will be used indifferently: air diffusing portion or air diffusion plenum. 
   In the great majority of devices of the prior art, the air diffuser is in a single block (that is to say it comprises only one air diffusion portion) and can be adjusted. 
   A first category of mobile aeraulic isolation devices comprises single block diffuser devices connected to their base (which includes an air purifying system) via a flexible duct to enable air to pass. 
   U.S. Pat. No. 4,163,650 Watson et al. describes a floor mobile device comprising a mobile cabinet on wheels equipped with decontamination means (formed of an ioniser and an electrofilter) and a fan. A hose is connected to the cabinet and leads to a conical-shaped diffuser. 
   U.S. Pat. No. 4,512,245 Goldman describes a device for local extraction of fumes comprising an air treatment unit connected by a flexible air suction tube to an exhaust outlet. 
   U.S. Pat. No. 5,129,928 Chan et al. describes a portable device for locally reducing the concentration of allergens in air. The system comprises a base fitted with a fan, pre-filters, and a flexible air duct leading to a conical diffusing head fitted with a filter. 
   U.S. Pat. No. 5,281,246 Ray et al. describes an air purifier intended to aspirate and filter fumes. It is formed of a cabinet on wheel, fitted with filters and fans. A conical deflector is connected to an articulated duct conveying the aspirated air towards the treatment cabinet. 
   U.S. Pat. No. 5,290,331 Miles et al. describes a cylindrical head for diffusing decontaminated air placed in a localised area, connected by a flexible air tube to an air ventilation and decontamination system. 
   The isolators in this first category, having a single block diffuser connected to an articulated or flexible duct, can only be used for treating air over small areas, owing to the mechanical impossibility of the duct to carry a large diffuser. 
   Patent DE 3639708 Kreyenberg Karl Heinz describes a variant of isolator in this first category, formed of a single block diffuser of semi-torus shape provided with air diffusion holes and connected via a flexible pipe to a box unit containing decontamination and air pressurizing means, placed on a floor mobile base frame. The diffusing torus is arched over the patient to create a protective air curtain of semi-cylindrical shape. 
   A second category of mobile aeraulic isolation device comprises single block air diffusing devices articulated on a mobile base frame. 
   U.S. Pat. No. 3,724,172 Wood describes an aseptic isolator with a diffuser joined to a mobile base frame and positioned at the head or side edge of the bed setting up a flow of air parallel to the mattress. In its versions adaptable to the head of the bed, the diffuser is fixed at the top of the mattress and can pivot with the latter. This device does not give satisfactory use since the diffuser is too close to the sensitive zone (patient&#39;s head and body) and the horizontal position of the air flow brings interference with the pillow and patient&#39;s body setting up turbulence. 
   U.S. Pat. No. 3,385,036 Webb describes an isolator with a conical diffuser fitted on the inside with a filter, placed at the end of a positioning arm mounted on a mobile frame, and connected to a fan integral with the frame via a flexible pipe. The diffuser is in a single block and can be inclined. 
   U.S. Pat. No. 3,820,536 Anspach, Jr et al. and U.S. Pat. No. 4,045,192 Eckstein et al and patent DE 20018765U Laflow Reinraumtechnik each describe an isolator formed of an articulated box unit mounted on a floor mobile frame, comprising decontamination and air pressurizing means and leading to an angle-adjustable single block diffuser. 
   U.S. Pat. Nos. 4,272,99 and 6,099,607 Haslebacher describe an isolator formed of a box unit containing decontamination and air pressurizing means placed on a floor mobile frame and connected to a single block air diffuser via a flexible articulated pipe. So that the single block diffuser is angle-adjustable. 
   U.S. Pat. No. 5,312,465 Riutta describes an isolator formed of a box unit comprising decontamination and air pressuring means, placed on a floor mobile frame and connected to a plenum made up of an inflatable bag fitted with a diffuser at its end. The diffuser is single block and angle-adjustable. 
   U.S. Pat. No. 5,487,766 Merlin R. Vannier describes an isolator formed of a floor mobile frame surmounted by a box unit fitted with a horizontal extraction hood, including decontamination and air pressurizing means, and surmounted by a horizontal single block diffuser with vertical lower diffusion. The diffuser is connected to the box by a height-adjustable air pipe so that the vertical position of the diffuser can be adjusted. 
   The isolators in this second category, with a single block diffuser articulated on a mobile chassis, are unable to provide both a sufficiently large diffusion surface for the horizontal coverage of a large-size sensitive area (greater than the size of a hospital bed for example, i.e. approximately 2.2 m×1 m) and possible passage through a doorway (approximately 0.8 m wide) smaller in size than the sensitive area. 
   A third category of mobile isolators comprises devices formed of a tent with an inner monolithic diffuser. A device of this type with a fixed bar frame is described in patent GB 1066145 Bunyan John. Another device of this type with a fixed frame in inflatable tubes is described in U.S. Pat. No. 5,832,929 Yamaha Isao et al. 
   The tent isolators in this third category with a monolithic diffuser have the drawback firstly of being distressing for persons inside, patients in particular; and secondly of having difficult access for care givers if these tents are used for patient isolation; and finally they require time-consuming installation procedure. 
   A fourth category of mobile aeraulic isolation device comprises variable geometry air diffusion devices of multi-block type; that is to say comprising several (at least two) plenums (air diffusion portions). This is the prior art that is closest to the invention. A device of this type is described in U.S. Pat. No. 3,935,803 Louis Bush. It is a mobile aeraulic isolation device for a sensitive zone (a bed) against contaminating airborne aerosols, also comprising a twin-block diffuser (or air diffusion chamber—that is to say with two connected plenum portions) giving this air diffuser variable geometry (that is to say mobility of one plenum portion relative to the other). 
   This isolation device comprises a console air diffuser made up of two rigid air diffusion plenums, mechanically connected to each other, and mobile relative to one another each having a lower planar air-diffusing surface that is porous to air. Means of relative movement, formed by a horizontal axis and fixation means in horizontal or vertical position, enable a second downstream mobile rigid air diffusion plenum positioned at one end to pivot relative to the other first, fixed, rigid upstream air-diffusing plenum. They also enable this second mobile rigid plenum to be tilted in relation to the chassis, in two distinct relative positions. In a first position shown in  FIG. 1 , which we call the fixed in-use position, the second mobile diffusing surface of the second mobile downstream plenum is horizontal and extends the first diffusing surface of the first fixed upstream rigid plenum connected to the chassis. These two diffusing surfaces form only one surface and are positioned horizontally facing and away from the floor. A flow of air curses through the two diffusing surfaces in a substantially vertical air direction covering the sensitive zone that is the bed. In operating use, the floor projecting surface of the second mobile downstream diffusing surface is maximal and covers the bed. The first diffusing surface of the first upstream plenum and the first upstream plenum are fixed relative to the chassis. 
   In the other position, shown in  FIG. 2  which we will call floor movement position, the downstream plenum is folded vertically. The floor projecting surface of the second mobile downstream diffusing surface is of minimal size. The floor projection of the first upstream diffusing surface of the fixed upstream plenum remains unchanged. 
   The device also comprises a vertical chassis-cabinet, whose width is substantially the same as the width of the bed and includes physical means for decontaminating moving air formed of filters and air pressurizing means formed by a fan. 
   Aeraulic connection and air circulation means (formed by this chassis-cabinet) aeraulically connect the fan, the filters and the two rigid air diffusion plenums of the air diffuser, forcing the air to pass through their air diffusing porous surfaces. 
   The mobile supporting chassis-cabinet is connected mechanically and rigidly to the first fixed upstream plenum and indirectly to the second mobile downstream plenum of the air diffuser. It gives rigid support to the cabinet containing the air decontamination filters, fan for pressurizing air and the aeraulic connection assembly. The chassis is fitted with means for horizontal movement of the chassis relative to the floor, formed of casters. 
   This mobile twin-block aeraulic isolation device of the prior art, with variable geometry diffuser, indeed has the advantage of being able to diffuse filtered air over the entire upper surface of a bed and can be folded away. 
   One first essential aspect of this device of the prior art is that it comprises only one plenum that is mobile relative to its mobile supporting chassis-cabinet, the other is fixed. 
   Yet there are two main sizes for hospital beds:
     Type 1: Europe and India, width 80 to 90 cm, length 190 to 200 cm;   Type 2: U.S. and Europe, width 91 to 110 cm, length 214 to 227 cm.   

   One consequence of the geometry of the system, apparent in the description, is that the minimum sizes of this system of the prior art to protect a hospital bed are:
     in opened, in-use position:
       height: 76 inches, i.e. 193 cm   length: 118 inches, i.e. 300 cm, of which 30 inches, i.e. 76.2 cm for chassis-cabinet thickness and 88 inches, i.e. 223 cm, for length of plenums   width: 47 inches, i.e. 120 cm.   
       in vertical, closed position for floor movement
       height: 76 inches, i.e. 193 cm   length: 68 inches, i.e. 173 cm   width: 47 inches, i.e. 120 cm   
       in closed position with 90° pivot floor movement
       height: 68 inches, i.e. 173 cm   length: 76 inches, i.e. 193 cm   width: 47 inches, i.e. 120 cm   
       

   It therefore appears that in folded position, the smallest dimension of this device of the prior art is its width (width of the plenums). It is therefore in longitudinal direction, that is to say along the axis of the plenums, that it passes more easily through a doorway. So that in folded position, the minimum door width through which the device can be passed is greater than the width of the bed it is to protect (i.e. 47 inches or 120 cm) and is equivalent to the width of its plenums. 
   Yet, outside the hospital (or industrial) environment, the most frequent door size found in homes is approximately 205 cm high and 80 cm wide i.e. 81 inches×31 inches. 
   So that the first defect of this system of the prior art, having a single mobile plenum, is that its geometry does not allow its use in home hospitalisation applications, in particular for the treatment of immunosuppressed patients at home, since it cannot pass through standard doorways. 
   A second defect of this system of the prior art is that the effective width of the plenums it can use is limited by door widths. So that the volume of protection surrounding the patient is itself restricted. This is adverse to patient comfort and protection. 
   A second essential particular aspect of this device of the prior art is that its physical means for air decontamination are chiefly located in the body of its chassis-cabinet and are formed of filters. On account of this configuration, the chassis-cabinet takes up much space: width substantially equivalent to that of the bed, 47 inches i.e. 120 cm and depth 30 inches i.e. 76 cm. So that either the chassis-cabinet is placed at the foot of the bed in which case it completely blocks out the patient&#39;s view in this direction, leading to a feeling of imprisonment detrimental to patient comfort. Also it also blocks out the view of medical staff attending the patient. In addition, its large size makes this configuration impossible in most rooms. Either the chassis-cabinet is placed at the head of the bed, as shown in  FIG. 1 . However the cabinet is the part of the device which requires the most vertical space. 
   So that a third defect of mobile aeraulic isolation devices with variable geometry, twin-block diffuser and one single mobile plenum (such as described above) is that when they are used to protect beds, the most sensitive area, the head of the bed is next to that part of the device which is the most closed and most voluminous vertically. It will be understood that this considerably hampers access by medical staff to the sensitive area via the head of the bed (which is the part of the bed which requires most access by attending staff: tube insertion, intravenous drips, disinfection, hygiene . . . ). So that these devices hinder the work of hospital staff. 
   In addition, the head of the bed is the area with the least available floor and vertical space. The treatment cabinet uses all the rear volume of the sensitive zone formed by the head of the bed. And the head of the bed is precisely where by tradition the majority of the room&#39;s technical equipment is located (monitoring equipment, resuscitation equipment, gas inlets . . . ) So that these devices disorganize and hinder the functioning of technical equipment. 
   A fourth defect of mobile aeraulic isolation devices with variable geometry twin-block diffuser and a single mobile plenum (such as described above) is that the mobile supporting trolley is of fixed geometry. For reasons of space, the length of the frame parts of this trolley is far smaller than the overall length of the diffuser when corbelled in opened operating use. It will be understood that on this account the device of the prior art has very precarious balance when opened for use. 
   A fifth defect of mobile aerological isolation devices with variable geometry twin-block diffuser and a single mobile plenum (as described above) is that the different mass parts (chassis-cabinet . . . ) giving counterweight to prevent collapse of the device when the corbelled diffuser is in open operating position, are fixed relative to the polygonal centre of sustentation. So that there is no means to offset displacement of the centre of gravity towards the free end of the device when the mobile plenum is opened for use. For this reason, the equilibrium of the device of the prior has further precariousness when opened for use. 
   A sixth defect of mobile aeraulic isolation devices with variable geometry twin-block diffuser (such as described above) is that their lateral air curtain is insufficient to prevent penetration inside the sensitive bed zone of Pflügge droplets emitted by visitors or attending staff when speaking, coughing or sneezing. These Pflügge droplets generally have a diameter of between 5 and 100 microns and are emitted at very high speed (at times close to the speed of sound). S that the curtain of air is not able to stop their passage on account of their high kinetic energy. This obliges visitors and attending staff to wear a mask close to the device if the device is used to protect a patient with very low immunity response, which is nonetheless its chief function. 
   A seventh defect of mobile aeraulic isolation devices with variable geometry twin-block diffuser (such as described above) is that their lateral air curtain is generally very noisy and energy-consuming. 
   An eighth defect of mobile aeraulic isolation devices with variable geometry twin-block diffuser (such as described above) is connected with their first particular aspect described above. The minimum lateral space required by this device in movement position is equivalent to the width of plenum protection. So that it is not possible provide these plenums with sufficient width so that, within the protected surface underneath the plenums, they can house visitors or attending staff and/or equipment to make life more pleasant for patients (tables, lounge chair, reading chair . . . ). Otherwise the device could not go through doorways. 
   SUMMARY OF THE INVENTION  
   The invention concerns a mobile aeraulic isolation device with multi-block, variable geometry air diffusion chamber to protect a sensitive area such as a bed against contaminating airborne aerosols. 
   The isolation device of the invention is of the type comprising an air diffusion chamber (or diffuser) formed of at least two rigid air diffusion plenums, mechanically connected to each other so that they are mobile relative to one another. Each of the two rigid plenums is delimited by an outer envelope of substantially parallelepiped shape (optionally dihedral) with substantially rectangular cross-section having an air diffusing undersurface that is substantially planar and porous to air, to allow air diffusion through it. The outer envelope of each plenum, at least at one first contact end, is provided with a first free end contacting surface (open) substantially perpendicular to the corresponding diffusing surface. This first free end contacting surface is surrounded by a so-called intermediate ring joint plane of substantially identical size and geometry for both rigid plenums. 
   The invention specifically relates to mobile plenum aeraulic isolation devices, that is to say also comprising means of relative movement for at least one first mobile plenum relative to the other second mobile plenum, and enabling them to be positioned relative to one another in at least two distinct relative positions, including a so-called open relative position and a so-called closed relative position. 
   In the open relative position, the first diffusing surface of the first mobile plenum is substantially coplanar and abutting, substantially in the extension of the second diffusing surface of the second mobile plenum. The intermediate joint planes of the mobile plenums are immediately adjacent so that the mobile plenums are hermetically coupled. 
   In the other so-called closed relative position, the first diffusing surface of the first mobile plenum does not lie in the extension of the diffusing surface of the second mobile plenum. Also, the intermediate joint planes of the mobile plenums are distanced from each other and uncoupled. 
   An aeraulic isolation device with mobile plenum according to the invention is of the type fitted with at least one physical means for decontaminating air moving through it, and with at least one air pressurizing means. It is equipped with aeraulic connection and air circulation means, which aeraulically connect the air pressurizing means, the physical air decontamination means and a second free inlet surface of at least one of the two rigid plenums of the air distribution chamber, forcing the flow of air to pass through the porous air diffusing surfaces when the plenums are in open, hermetically coupled position. 
   An aeraulic isolation device with mobile plenum of the invention is of the type placed on a mobile supporting chassis, mechanically connected to the two rigid plenums of the air diffusion chamber, to the one or more physical air decontamination means, to the air pressurizing means and to the aeraulic connection means. This mobile supporting chassis is equipped with means for horizontal movement of the chassis relative to the floor. 
   One first particular aspect characteristic of the mobile aeraulic isolation device of the invention compared with mobile plenum systems of the prior art is that, in addition, it comprises at least one complementary means for absolute movement of the group of two rigid plenums relative to the mobile supporting chassis. So that that mobile aeraulic isolation device with mobile plenums of the invention is easily recognizable in that its first rigid plenum and its second rigid plenum for air diffusion are both mobile, both relative to one another and relative to the chassis. 

   
     DRAWINGS AND FIGURES  
     In the remainder of the description and drawings, three different variants of embodiment of the invention will be described, differing in the nature of the combined kinematics:
     of the relative movement means for the first upstream mobile plenum relative to the second downstream mobile plenum,   and of the complementary means of absolute movement for the group of two rigid plenums relative to the mobile supporting chassis.   

     Therefore: 
       FIGS. 1 to 10   a  show a first variant of embodiment of a mobile aeraulic device ( 1   a ) of the invention provided with:
     means of relative movement for the plenums which slide into one another drawer-fashion,   complementary means of absolute movement for the group of two rigid plenums, of horizontal rotating axis type for absolute movement joining the mobile supporting chassis and one of the plenums.   
       FIG. 1  is a left view of a mobile aeraulic isolation device  1   a , in closed position (floor movement) passing through a doorway. 
       FIG. 2  is a left view of a mobile aeraulic isolation device  1   a , in open position (fixed in use) covering a hospital bed. 
       FIG. 3   a  is an upper rear perspective view of a mobile aeraulic isolation device  1 A (of standard plenum width type) in open position (fixed in use) covering a hospital bed. 
       FIG. 3   b  is an upper rear perspective view of a mobile aeraulic isolation device  1   a  (of large plenum width type) in open position (fixed in use) covering a hospital bed. 
       FIG. 4  is a front perspective view of a mobile aeraulic isolation device  1   a  in closed position (for floor movement). 
       FIG. 5  is a rear perspective view of a mobile aeraulic isolation device  1   a  in closed position (for floor movement). 
       FIGS. 6   a  and  6   b  are left upper(overhead) rear perspective views of the diffuser and of a mobile aeraulic isolation device  1   a  in open position (fixed in use). 
       FIG. 7  is a front lower perspective view of a mobile aeraulic isolation device  1   a  in open position (fixed in use). 
       FIG. 8  is a rear perspective exploded view of a mobile aeraulic isolation device  1   a  in open position (fixed in use). 
       FIGS. 9   a  to  9   h  are rear upper perspective views of the different phases of setting up a mobile aeraulic isolation device  1   a  from closed position (for floor movement) to open position (fixed in use): 
       FIG. 9   a : in floor movement position, global recessed vertical position of the plenums, with downstream plenum folded drawer fashion inside the upstream plenum, feet raised, 
       FIG. 9   b : global recessed position, with downstream plenum folded, feet lowered, 
       FIG. 9   c : global recessed position, with downstream plenum folded, feet lowered, shoe blocks resting 
       FIG. 9   d : global intermediate position with downstream plenum folded, and partial rotation of the group of two plenums, 
       FIG. 9   e : global horizontal forward position of plenums, with downstream plenum folded, 
       FIG. 9   f : global horizontal, forward position of plenums, with downstream plenum half-opened, 
       FIG. 9   g : global horizontal forward position of the plenums, with downstream plenum opened and covering a bed, 
       FIG. 9   h : in use mode with curtains and covering a bed. 
       FIG. 10  is a detailed left view of a mobile aeraulic isolation device  1   a , showing the arrangement of the gravity effect compensation means(jacks) on the plenums. 
       FIGS. 11 to 20  show a second variant of embodiment of a mobile device  1   b  for aeraulic isolation according to the invention, provided with:
     means for relative movement of the plenums by rotation about a mobile horizontal axis of relative movement connected to both of the plenums,   and complementary means for absolute movement of the group of two rigid plenums, of fixed horizontal rotating axis type for absolute movement connected to the mobile supporting chassis and to one of the plenums.   
       FIG. 11  is a left view of a mobile aeraulic isolation device  1   b  in closed position (for floor movement) when passed through a doorway. 
       FIG. 12  is a left view of a mobile aeraulic isolation device  1   b  in open position (fixed in use) covering a hospital bed. 
       FIG. 13  is an upper rear perspective view of a mobile aeraulic isolation device  1   b  in open position (fixed in use) covering a hospital bed. 
       FIG. 14  is a front perspective view of a mobile aeraulic isolation device  1   b  in closed position (for floor movement). 
       FIG. 15  is a rear perspective view of a mobile aeraulic isolation device  1   b  in closed position (for floor movement). 
       FIGS. 16   a  and  16   b  are left views and in upper rear perspective of the diffuser and mobile aeraulic isolation device  1   b  in open position (fixed in use). 
       FIG. 17  is a lower front perspective view of a mobile aeraulic isolation device  1   b  in open position (fixed in use). 
       FIG. 18  is a rear exploded perspective view of a mobile aeraulic isolation device  1   b  in open position (fixed in use). 
       FIGS. 19   a  to  19   h  are an upper rear perspective views of the different phases in setting up a mobile aeraulic isolation device  1   b  from a closed position (floor movement) to the open position (fixed in use). 
       FIG. 19   a : in floor movement mode, global vertically recessed position of plenums with downstream plenum folded against the upstream plenum, feet raised, 
       FIG. 19   b : global recessed position, with downstream plenum folded, feet lowered, 
       FIG. 19   c : global recessed position, with downstream plenum folded, feet lowered, shoe blocks resting 
       FIG. 19   d : intermediate global position with downstream plenum folded and partial rotation of the group of two plenums, 
       FIG. 19   e : global horizontal forward position of the plenums with downstream plenum folded, 
       FIG. 19   f : global horizontal forward position of the plenums with downstream plenum half-opened, 
       FIG. 19   g : global horizontal forward position of plenums with downstream plenum opened and covering a bed, 
       FIG. 19   h : in-use mode with curtains, covering a bed. 
       FIG. 20  is a detailed view of the relative rotation axis of the plenums in a mobile aeraulic isolation device  1   b  according to the invention. 
       FIGS. 21 to 33A  show a third variant of embodiment of a mobile aeraulic isolation device  1   c  according to the invention, provided with:
         means for relative movement of the plenums by rotation about a mobile horizontal axis for relative movement connected to both plenums,   complementary means for absolute movement of the group of two rigid plenums, of the type with horizontal translation of the mobile horizontal axis for relative movement.       
       FIG. 21  is a left view of a mobile aeraulic isolation device  1   c  in closed position (for floor movement) passing through a doorway. 
       FIG. 22  is a left view of a mobile aeraulic isolation device  1   c  in open position (fixed in use) covering a hospital bed. 
       FIG. 23  is a rear perspective view of a mobile aeraulic isolation device  1   c  in open position covering a hospital bed. 
       FIG. 24  is a front perspective view of a mobile aeraulic isolation device  1   c  in closed position. 
       FIG. 25  is a rear perspective view of a mobile aeraulic isolation device  1   c  in closed position. 
       FIGS. 26   a  and  26   b  are left views in upper front perspective of the diffuser of a mobile aeraulic isolation device  1   c  in open position with hoods dismounted. 
       FIG. 27   a  is a front perspective view of a mobile aeraulic isolation device  1   c  in closed position, hoods removed. 
       FIG. 27   b  is a front perspective view of the hoods of a mobile aeraulic isolation device  1   c  in closed position. 
       FIGS. 28   a  to  28   f  show the different phases in setting up a mobile aeraulic isolation device  1   c , from closed position (so-called floor movement position) to open position (so-called fixed in use position): 
       FIG. 28   a : closed position next to a hospital bed, left view, 
       FIG. 28   b : semi-closed position with rotation axis of plenums brought forward, front perspective view, 
       FIG. 28   c : semi-closed position: with rotation axis of plenums brought forward and front plenum raised and fixed, front perspective view, 
       FIG. 28   d : open position, with rotation axis of plenums brought forward, front and back plenums raised and fixed, hoods partially open, in bottom position, front perspective view, 
       FIG. 28   e : open position with rotation axis of plenums brought forward, front and rear plenums raised and fixed, hoods closed, in top position, front perspective view, 
       FIG. 28   f : opened, top position on hospital bed, rear perspective view. 
       FIG. 29   a  is a detailed view in upper front perspective of the sliding means for the rotation axis of the mobile plenums and of the means for locking the front plenum relative to the chassis. 
       FIG. 29   b  is a detailed view in rear perspective of the mobile, releasable interlocking means of the mobile plenums. 
       FIGS. 30   a  and  30   b  are front perspective partial left side views of the chassis alone in closed position. 
       FIG. 31  is front perspective view of the chassis alone in open position. 
       FIG. 32  is front perspective view of the chassis in open position equipped with its plenums, physical decontamination means and aeraulic connection means. 
       FIG. 33   a  is detailed rear perspective view showing the air intake of the physical decontamination means and the base of the chassis. 
       FIG. 33   b  is a schematic diagram of the principle of inner organization of the physical decontamination means. 
   

   DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE FIGURES  
     FIGS. 1 to 10   a  show a mobile aeraulic isolation device  1   a  of the invention in a first variant of embodiment comprising:
         means for relative movement  10  of plenums  5 , 6  of the type in which they slide into one another drawer-fashion,       and complementary means for absolute movement  13  of the group of two plenums  5 , 6 , of horizontal rotating axis type  13   a  for absolute movement connected to the upper part of the mobile supporting chassis  12  and to the upstream mobile plenum  5 .   
   A mobile aeraulic isolation device  1   a  according to this first variant of the invention is shown: in global closed position, so-called floor movement position M in  FIG. 1 ; and in global open position, so called fixed in-use position U covering a hospital bed  191  in  FIG. 2 . The mobile aeraulic isolation device  1   a  is intended, in open fixed position for use U, to protect a sensitive area  2  formed by the hospital bed in particular  191 , against contaminating airborne aerosols (not shown) in the patient&#39;s room. It will be subsequently understood that on account of the great mobility of the device  1   a , the bed  191  to be protected can be located in a hospital or at home. It will also be understood that the mobile aeraulic isolation device  1   a  of the invention may be used to protect any localized sensitive area, an industrial area in particular, and not solely for medical applications. 
   It will be noted that the mobile aeraulic isolation device  1   a  is equipped with a twin-block air diffusion chamber (or diffuser)  4  of variable geometry type. With reference to  FIGS. 7 and 8 , it can be seen that the diffusion chamber  4  of the isolation device  1   a  is formed of two rigid air diffusion plenums, one upstream  5  and the other downstream  6  mechanically joined to one another and mobile relative to one another. Each of the two rigid plenums  5 , 6  is delimited by an outer envelope  5   a ,  6   a , of substantially parallelepiped shape with rectangular cross section  5   b ,  6   b  delimiting a hollow inner volume. As shown in  FIG. 7 , each envelope  5   a ,  6   a  of plenums  5 , 6  has a lower air diffusing surface  7 , 8  substantially planar and porous to air to enable the diffusion of air through it. Such as shown in  FIG. 8 , each envelope  5   a ,  6   a , at one first contact end at least  5   c ,  6   c , is provided with a first free end contacting surface  5   e ,  6   e  substantially perpendicular to the corresponding diffusing surface  7 , 8 , surrounded by so-called intermediate rectangular ring joint plane  5   d ,  6   d  whose size and geometry is substantially identical for both rigid plenums  5 , 6 . 
   With reference to  FIGS. 9   e  to  9   h , it can be seen that the mobile aeraulic isolation device  1   a  is fitted with means for relative movement  10  of the first upstream mobile plenum  5  relative to the other second mobile downstream plenum  6 . This makes it possible to move and position plenums  5 , 6  relative to one another in at least two distinct relative positions. 
   In a so-called open relative position (OP) shown in  FIGS. 2 ,  7 ,  9   g  and  9   h , the first diffusing surface  7  of the first upstream mobile plenum  5  is substantially coplanar and abutting substantially in the extension of the second diffusing surface  8  of the second downstream mobile plenum  6 . Also, intermediate joint planes  5   d ,  6   d  of the mobile plenums (hidden in the figures) are immediately adjacent so that mobile plenums  5 , 6  are hermetically coupled. 
   In another closed relative position (CL) shown in  FIGS. 1 ,  5  and  9   a  to  9   e , the first diffusing surface  7  of the first upstream mobile plenum  5  does not lie in the extension of diffusing surface  8  of the second downstream mobile plenum  6 . The intermediate joint planes  5   d ,  6   d  (hidden in the figures) of the mobile plenums are distanced from one another and uncoupled. 
   In exploded view  FIG. 8  it can be seen that the mobile aeraulic isolation device  1   a  is equipped with physical decontamination means  20 , 21 , 22 , 23  for moving air passing through it, and with air pressurizing means  25 , in particular a fan  330 . Aeraulic connection and air circulation means  30  formed by a hollow parallepid column  331  and an upper distribution caisson  332  joined to it, aeraulically connect the air pressurizing means  25 , physical decontamination means  20 , 21 , 22 , 23  and a second free intake surface  5   f  of the first upstream plenum  5  of the two rigid plenums  5 , 6  of air distribution chamber  4 . The second downstream mobile plenum  6  has a second closed end surface  6   f.    
   As shown in  FIG. 2 , the flow of air F is therefore forced to pass through porous, air diffusing surfaces  7 ,  8  when the two plenums  5 , 6  are in open position OP and hermetically coupled and when air pressurizing means  25  are activated. 
     FIG. 8  in particular shows that the mobile aeraulic isolation device  1   a  comprises a mobile supporting chassis  12 , mechanically connected to the two rigid plenums  5 , 6  of air diffusion chamber  4 , to the physical air decontaminating means  20 , 21 , 22   23 , to air pressurizing means  25  and to the aeraulic connection means  30  formed by a hollow parallelepiped column  331  and upper distribution caisson  332 . The mobile supporting chassis  12  is equipped (described below) with horizontal movement means  40  for the chassis  12  relative to floor  15 . 
   One first essential provision, characteristic of the invention is apparent in  FIGS. 1 and 2 . It will be seen that mobile aeraulic isolation device  1   a  comprises complementary means for absolute movement  13  of the group of two rigid plenums  5 , 6  relative to the supporting chassis  12 . It arises from the kinematics diagram of the opening process shown in  FIGS. 9   a  to  9   h —using the combined action of relative movement means  10  for mobile plenums  5 , 6  relative to one another and of complementary means  13  for absolute movement of the group of two plenums  5 , 6 —that the first rigid plenum  5  and second rigid plenum  6  for air diffusion are both mobile both relative to one another and relative to chassis  12 . 
   A second essential provision, characteristic of the invention is that the opening kinematics of mobile aeraulic isolation device  1   a  via the combination of relative movement means  10  and absolute movement means  13  make it possible to position mobile plenums  5 , 6  in at least two global positions relative to chassis  12 . 
   In a so-called fixed in-use global position U regarding sensitive area  2  shown in  FIGS. 2 and 9   h , the two plenums  5 , 6  are placed in relative open position OP via relative movement means  10 . So that the first diffusing surface  7  of the first upstream mobile plenum  5  is substantially coplanar and abutting substantially in the extension of the second diffusing surface  8  of the second downstream mobile plenum  6 . The intermediate joint planes  5   d ,  6   d  positioned inside the mobile plenums are immediately adjacent. The mobile plenums  5 ,  6  are coupled. This is hidden in the figures. And as shown in  FIGS. 9   g  and  9   h  the group of two plenums  5 , 6  in relative open position OP is by combination placed in absolute (horizontal) position distanced (AV) from chassis  12  through absolute movement means  13 . In this way, the first mobile diffusing surface  8  of the first upstream mobile plenum  5  and the second mobile diffusing surface  7  of the second downstream mobile plenum  6  are horizontal and positioned facing the floor  15  but away from it. As shown in  FIG. 2  the consequence is that the flow of clean air F passing through diffusing surfaces  7 , 8  is diffused in a substantially vertical air direction zz′ covering sensitive area  2 . Also, it will be noted that the projection surface PU 1  on floor  15  of the first mobile diffusing surface  7  and the projection surface PU 2  on floor  15  of the second mobile diffusing surface  8  are of respective maximum size LU 2 , LU 1 . 
   In the other global position, so-called floor movement position M, shown in  FIGS. 1 ,  4 ,  5  and  9   a , the two plenums  5 , 6  are placed in closed relative group position CL via relative movement means  10 . In this relative position the first diffusing surface  7  of the first upstream mobile plenum  5  does not lie in the extension of diffusing surface  8  of the second downstream mobile plenum  6 . Also, intermediate joint planes  5   d ,  6   d  of mobile plenums  5 , 6  are distanced from one another and uncoupled. This is masked in the figures. The group of two plenums in closed relative position CL is at the same time placed in absolute (vertical) recessed position RE relative to chassis  12  via absolute movement means  13 . In this way, the floor projection surface PM 1  of the first mobile diffusing surface  7  of the first upstream mobile plenum  5  and the floor projection PM 2  of the second mobile diffusing surface  8  of the second downstream mobile plenum  6  are of minimum size LM 1 , LM 2  (here zero) both much smaller than their maximum sizes LU 2 , LU 1  mentioned above. 
   With reference to  FIGS. 1 and 2 , it is found that relative movements means  10  for rigid plenums  5 , 6  of the mobile aeraulic isolation device  1   a  ensure relative movement of the two rigid plenums  5 , 6  relative to one another in at least two distinct relative positions. In open relative position OP shown in  FIG. 2 , the first diffusing surface  7  of the first mobile plenum  5  is substantially coplanar and abutting with the second diffusing surface  8  of the second mobile plenum  6 . A third characteristic of the invention is that, in addition, in the closed relative position CL shown in  FIG. 1 , the first diffusing surface  7  of the first upstream mobile plenum  5  is substantially opposite the second diffusing surface  8  of the second downstream mobile plenum  6 . It will indeed be understood that since the second downstream plenum  6  slides inside the first upstream plenum  5 , their diffusing surfaces  7 , 8  are opposite one another. Also, it is seen that relative movement means  10  for plenums  5 , 6  is mobile relative to chassis  12  via complementary absolute movement means  13  for the group of two rigid plenums  5 , 6 , and in absolute movement between the two absolute recessed RE and distanced AV positions. 
   A fourth provision, characteristic of the recommended use of mobile aeraulic isolation device  1   a  of the invention lies in the fact that its relative movement means  10  for plenums  5 , 6  shown in more detail in  FIGS. 6   a  and  7 , is made up of drawer-fashion sliding means  11   c . This is achieved through side sliding rails  334  ensuring this sliding of envelope  6   a  of the second downstream mobile plenum  6  inside envelope  5   a  of the first upstream mobile plenum  5 . On account of this drawer-like recessing, it will be understood that in closed relative position CL the outer  7   a  and inner  7   b  surfaces of first diffusing surface  7  of the first upstream mobile plenum  5  and the inner  8   a  and outer  8   b  surfaces of second diffusing surface  8  of the second downstream mobile plenum  6  are stacked in alternate manner. 
   A fifth provision, characteristic of recommended use of the mobile aeraulic isolation device  1   a  of the invention, consists of providing it with complementary sealed closing means  300  in closed relative position CL. These are shown in  FIG. 6   a  in open position OP. But it will be understood that these complementary sealed closing means  300  come into sealed contact with the first free contact surface  5   e  positioned at the first contact end  5   c  of the first rigid upstream plenum  5  when the two rigid plenums  5 , 6  are in closed relative position CL and the intermediate joint planes  5   d ,  6   d  (not visible in the figure) of mobile plenums  5 , 6  are distanced from one another and uncoupled. The complementary sealed closing means  300  of the first free contact surface  5   e  positioned at the first contact end  5   c  of the first rigid plenum  5  are formed by a second rectangular ring joint closing plane  6   g  surrounding the second closed end surface  6 f of the second mobile plenum  6 . The latter is pinned in sealed manner against a second rectangular ring joint closing plane  5   g  outwardly surrounding the first free end contacting surface  5   e  positioned at the first contact end  5   c  of envelope  5   a  of the first rigid plenum  5 ; at the same time when the two mobile plenums  5 , 6  are in closed relative position CL. This fifth characteristic provision makes it possible to use the mobile aeraulic isolation device  1   a  according to two size geometries for the diffusion chamber and floor surface area, and for different surfaces of sensitive area  2 . In particular, it can be used with the plenums in open position OP to protect an adult patient&#39;s bed, positioned longitudinally—and with the plenums in closed position CL to protect a cot, positioned crosswise. 
   A sixth provision, characteristic of recommended use of the mobile aeraulic isolation device  1   a  of the invention is shown in  FIG. 10   a . It consists of equipping it with gravity effect compensation means  301  (jacks in particular) to offset the weight of mobile plenums  5 , 6  in their movement relative to the chassis  12 . This facilitates opening operations between absolute recessed position RE and absolute distanced position AV. These gravity effect compensation means  301  are integral both via one of the ends  301   a  of upstream mobile plenum  5  and via the other end  301   b  of supporting chassis  12 . 
   A seventh provision, characteristic of recommended use of the mobile aeraulic isolation device  1   a  of the invention is shown in  FIG. 8 . It consists of arranging the physical decontamination means  20 , 21 , 22 , 23  equipping the mobile aeraulic isolation device  1   a  opposite a second free intake surface  5   f  of at least one of the two rigid plenums  5 , 6 , in particular the first upstream plenum  5 . According to the described variant of the mobile aeraulic isolation device  1   a , the physical decontamination means  20 , 21 , 22 , 23  are placed in a decontamination caisson  302  placed opposite the second free intake surface  5   f  of the first rigid plenum  5 . This decontamination caisson  302  is mechanically integral with and hermetically connected with this corresponding second free intake surface  5   f  of envelope  5   a  of the first upstream plenum  5 . So that physical decontamination means  20 , 21 , 22 , 23  are mobile relative to chassis  12  through the complementary absolute movement means  13  of the group of two plenums  5 , 6 . The decontamination means  20 , 21 , 22 , 23  are pinned against and fixed via their rear surface to a supporting plate  336  pierced with air passage holes. This bearing plate  336  is itself fixed around its edges to decontamination caisson  302 . 
   An eighth provision, characteristic of recommended use of the mobile aeraulic isolation device  1   a  of the invention is also shown in  FIG. 8 . This shows a downstream group of muffling elements  313   b  positioned downstream from the air pressurizing means  25  and formed of a plurality of panels  316   a  made of soundproofing material. The panels are arranged vertically and set at intervals inside hollow column  331  of frame  12 . Column  331  is closed by two sealed doors  332   a ,  332   b.    
   A ninth provision, characteristic of recommended use of the mobile aeraulic isolation device  1   a  is shown in  FIGS. 3   a ,  4 ,  5  and  8 . According to this first variant of embodiment, the mobile aeraulic isolation device  1   a  comprises complementary absolute movement means  13  for the group of two rigid plenums  5 , 6  formed of a fixed axis of absolute rotation  13   a  fixed to chassis  12 . It will be understood that this arrangement ensures relative rotation movement for physical decontamination means  20 , 21 , 22 , 23  and their caisson  302  relative to supporting chassis  12 , from front to back, via the complementary means of absolute movement  13  for the group of two rigid plenums  5 , 6  around the axis of absolute rotation  13   a , during their absolute movement between absolute distanced position AV and absolute recessed position RE. 
   A tenth provision, characteristic of recommended use of the mobile aeraulic isolation device  1   a  is described with reference in particular to  FIGS. 3 ,  4  and  6   b . It is seen that the mobile supporting chassis  12  of the mobile aeraulic isolation device  1   a  has at its base a lower mobile trolley  125  in the shape of a fork  126  formed of at least two supporting arms  127 , 128  that are horizontal, parallel and distanced from one another. The supporting arms  127 , 128  of chassis  12  are made up of several horizontal portions  131 , 132 , 133 , 134 , 135 , 136  connected together and mobile relative to one another. In the described solution, the front mobile portions  133  and  136  pivot about a horizontal axis aj 1 ,aj 2  relative to rear horizontal portions  131  and  134 . Portions  132  and  135  are sliding sleeves which take part in locking the different portions to one another. 
   Fixed portions  131 ,  134  of lower fork  126  of mobile trolley  125  have wheels  141 , 142 , 143 , 144  with a horizontal rotating axis Ir. Mobile portions  133 ,  136  are fitted with support shoes  335 ,  336  to improve the equilibrium of the device  1   a  when in in-use position U such as described in  FIG. 6   b.    
   An eleventh provision, characteristic of recommended use of the mobile aeraulic isolation device  1   a , is described with particular reference to  FIG. 2 . The mobile aeraulic isolation device  1   a  comprises vertical channelling means  150  for airflow for in-use position U. These are formed of two transparent plastic curtains  151 , 152  fixed to linear hanging supports  310 , 311  integral with the lower part  167  and on the periphery P of diffusing surfaces  7 , 8  of plenums  5 , 6  of the air diffusion chamber  4 . These linear hanging means  310 , 311  are formed of a first linear supporting portion  310  integral with the first upstream plenum  5  and a second linear supporting portion  311  integral with the second downstream plenum  6 . SO that the two linear supporting portions  310 , 311  are mobile relative to one another through relative movement means  10  and are both mobile relative to chassis  12  through the complementary absolute movement means  13  for the group of two plenums  5 , 6 . In addition, a plurality of mobile hanging rings of quarter turn type  310   a ,  311   a , are fixed in removable manner on linear supporting portions  310 , 311 . The two curtains  151 , 152  comprise a plurality of equidistant metal eyelets  310   b ,  311   b  positioned on their upper edge each one engaged in the corresponding rings. This allows for quick fixing and dismounting of the two curtains  151 , 152  on the periphery P of diffusing surfaces  7 , 8 . 
   A twelfth advantageous provision for use of the mobile aeraulic isolation device  1   a  is described with reference to  FIG. 3   a . Some of the curtains and in particular the bed-head panel  155   a  of curtain  155  positioned on the second downstream plenum  6 , distanced from chassis  12  when opened for use—position OP, comprise at least one portal hole for utilities  312 . This portal  312  is formed of a metal frame  155   b  substantially oblong, resting via its edges on panel  155   a  and binding a soft membrane in PTFE  312   a  provided with cross cuts  312   b  for the practically sealed passing of utility tubes  338  such as: oxygen, vacuum, air. 
   A thirteenth advantageous provision for use of the mobile aeraulic isolation device  1   a  is that, in complementary fashion, the other side surfaces of the two curtains  151 , 152  are provided, substantially at mid-height, with holes whose closure can be deactivated  340 . This enables the passing of small-sized items required for patient care such as trays, instruments. In the embodiment described in  FIG. 3   a , these are of “letter-box flap door” type. They enable the relative overpressure of the isolated area to be maintained above the sensitive surface  2  when inserting or withdrawing items. It is not necessary to open the curtains. 
   A fourteenth advantageous provision for use of the mobile aeraulic isolation device  1   a  concerns the configuration of its aeraulic means described in  FIG. 8 . Air pressurizing means  25  and aeraulic connection  30  and air circulation means are positioned inside a vertical hollow column  331  of chassis  12 , closed by sealed doors  332   a ,  332   b . The air intake  342  of device  1   a  is positioned substantially horizontally below and in the lower part  198  of aeraulic connection column  331  of chassis  12  opposite the plane of the sensitive area  2  (floor  15  in particular). 
   A fifteenth advantageous provision for use of the mobile aeraulic isolation device  1   a  is shown in  FIG. 8 . It consists of equipping the mobile aeraulic isolation device la with means  313  to muffle noise conveyed by the air chiefly produced by air pressurizing means  25 . These sound muffling means  313  are positioned inside the vertical column  331  of chassis  12 . 
   Preferably, these muffling means  313  for air-conveyed noise are made up of two groups of muffling elements  313   a ,  313   b  positioned inside vertical column  331  of chassis  12  of which one  313   a  is positioned upstream and the other  313   b  is positioned downstream from the air pressurizing means  25 . The muffling means  313  for air-conveyed noise are preferably according to the invention formed of panels  316  in sound-absorbing material. For this purpose a microbiologically neutral material is advantageously used, such as glass wool panels whose two surfaces and edges are coated with a protective PTFE film. One provision recommended by the invention is that muffling means  313  for air-conveyed noise are made up of:
         firstly, an upstream group of muffling elements  313   a , positioned upstream from air pressurizing means  25  and formed by at least one panel  316   a  of noise absorbing material arranged horizontally,   and secondly, a downstream group of muffling elements  313   b , positioned downstream from air pressurizing means  25  and made up of a plurality of panels  316   a  in noise absorbing material, arranged vertically and distanced from one another inside column  331  of chassis  12 .       

   A sixteenth advantageous provision for use of the mobile aeraulic isolation device  1   a , concerns an industrial embodiment of the lower air diffusing surface  7 , 8  of the two mobile plenums  5 , 6  of the mobile aeraulic isolation device  1   a  described in  FIG. 7 . According to this embodiment, the lower air diffusing surface  7 , 8  of the two mobile plenums  5 , 6  is formed of a plurality of panels  318  (substantially rectangular) made in plastic material (epoxy glass in particular called FR4 routinely used for printed circuits) pierced with a multitude of cylindrical holes  318   a  uniformly distributed over surface  318   b  of each panel  318 . Preferably the lower air diffusing surface  7 , 8  in plastic material of the two plenums  5 , 6  is formed of a combination between: two frames  321 , 322  mobile relative to chassis  12 , that are substantially rectangular, mechanically and hermetically connected around their periphery P to the lower part of outer envelopes  5   a ,  6   a  of the two plenums  5 , 6  and provided with a multitude of cross braces  321   a ,  321   b ,  322   a ,  322   b  and with a plurality of panels  318  (substantially rectangular) in plastic material (epoxy glass in particular) pierced with a multitude of cylindrical holes  318   a  uniformly distributed. Panels  318  are placed edge to edge and screwed around their periphery to the cross braces  321   a ,  321   b ,  322   a ,  322   b.    
   With reference to  FIGS. 2 and 3 , a particularly effective application of the invention can be seen. 
   An aeraulically decontaminated hospital bed  190  of the invention is formed by the combination between:
     a bed  191  for an immunosuppressed patient—and a mobile aeraulic isolation device  1   a  of the invention such as described above. Device  1   a  is mounted on a chassis  12 . Its air diffuser  4  comprises at least two rigid mobile air diffusion plenums  5 , 6  mechanically connected to one another. The mobile aeraulic isolation device  1   a  placed in in-use position U. Its plenums  5 , 6  are in open relative position OP through relative movement means  10  according to which the first diffusing surface  7  of the first mobile plenum  5  is substantially coplanar, abutting and substantially in the extension of the second diffusing surface  8  of the second mobile plenum  6 . Also, the group of plenums  5 , 6  is in absolute distanced position AV relative to chassis  12  through absolute movement means  13  so that the projection surface of the two plenums substantially covers the surface of the bed.   

   An aeraulically decontaminated hospital bed  190  of the invention is recognisable in particular by the fact that its rigid plenums  5 , 6  are mobile relative to one another and both plenums are mobile relative to chassis  12  of the mobile aeraulic isolation device  1   a ,  1   b ,  1   c.    
   One configuration preferred by the invention for an aeraulically decontaminated bed  190  is remarkable in that mobile chassis  12  of the mobile aeraulic isolation device  1   a  and its decontamination means  20 , 21 , 22 , 23  are arranged at the foot of bed  191 , and in that the second rigid downstream mobile plenum  6  for air diffusion the furthest away from chassis  12  is positioned on the side of and above the head of bed  191 . 
     FIG. 3   a  describes a mobile aeraulic isolation device  1   a  in use position U, in which the width of the plenums is substantially equal to the width of bed  191  it is to protect. 
   A seventeenth advantageous provision for use of the mobile aeraulic isolation device  1   a  is described in  FIG. 3   b . The mobile aeraulic isolation device  1   a  is equipped with plenums whose width is substantially equivalent to 1.5 times the width of bed  191  it protects. 
   With this provision it is possible to protect the sensitive area, such as the patient and the bed together with accessories, furniture (chair, console, hygiene equipment, . . . ) and monitoring or treatment devices. This also allows attending staff or visitors to be included under the flow, thereby limiting opening and closing of the curtains and providing improved protection. 
     FIGS. 11 to 20  show a mobile aeraulic isolation device  1   b  of the invention in a second variant of embodiment comprising:
         relative movement means  10  for plenums  5 , 6  of the type with rotation about a mobile horizontal axis for relative movement  11   a  connected to both plenums  5 , 6 ,   complementary means for absolute movement  13  of the group of two plenums  5 , 6  of the type with horizontal rotating axis  13   a  connected to the upper part of mobile supporting chassis  12  and to the upstream mobile plenum  5 .       
   A mobile aeraulic isolation device  1   b  according to this second variant of the invention is shown: in global closed position, so-called floor movement position M in FIG.  11 —and in global open position, so-called fixed in-use position U covering a medical bed  191  in  FIG. 12 . 
   It will be seen that the aeraulic isolation device  1   b  of this second variant identically reproduces most particular aspects of aeraulic isolation device  1   a  described above in the first variant. The common elements are denoted with the same references in drawings  11  to  20 . It appears unnecessary to repeat their description. 
   AN eighteenth advantageous provision for use of the mobile aeraulic isolation device  1   b  is seen in FIGS.  13 , 14  and  15 . Its relative movement means  10  for plenums  5 , 6  is formed by a relative rotation axis  11   a  around a hinge connected respectively to each of the first two contact ends  5   c ,  6   c  of the envelope of plenums  5 , 6 . 
   This hinge forming the relative rotation axis  11   a  is shown in more detail in  FIG. 20 . It will be understood that the relative rotation axis  11   a  of mobile plenums  5 , 6  is itself mobile relative to mobile supporting chassis  12  via the complementary means  13  of absolute movement for the group of two plenums  5 ; 6   
   A nineteenth advantageous provision for use of the mobile aeraulic isolation device  1   b  is shown in FIGS.  13 , 14 , 16  and  17 . The mobile aeraulic isolation device  1   b  comprises mobile releasable means  17 , 305 , 306  for relative interlocking of rigid plenums  5 , 6  in their relative movement. They are formed of interlocking elements  305   a ,  305   b ,  306   a ,  306   b  integral with plenums  5 , 6  ensuring firstly their locking in open relative position OP, so that mobile plenums  5 , 6  are coupled rigidly and hermetically and their first and second diffusing surfaces  7 , 8  are coplanar, and ensuring secondly their unlocking for placing in closed relative position CL. It will be seen that the different interlocking elements  305   a ,  305   b ,  306   a ,  306   b  of this mobile releasable relative interlocking means  17  of plenums  5 , 6  are integral with plenums  5 , 6  and fully mobile relative to mobile supporting chassis  12  via relative movement means  10  and complementary absolute movement means  13 . 
     FIG. 17  shows that device  1   b  also comprises a second group of interlocking elements  303 , 304  for the first upstream plenum  5  relative to chassis  12 . These are intended to ensure locking of the group of two plenums  5 , 6  in absolute forward position AV, and when released to ensure closing in absolute recessed position RE during rotation around the horizontal rotating axis of absolute movement  13   a.    
     FIGS. 21 to 33   a  show a mobile aeraulic isolation device  1   c  of the invention in a third variant of embodiment comprising:
         relative movement means  10  for plenums  5 , 6  of the type with rotation around a mobile horizontal axis of relative movement  11   a  connected to both plenums  5 , 6 ,   and complementary means of absolute movement  13  for the group of two plenums  5 , 6  of the type with horizontal translation of the mobile horizontal axis of relative movement.       
   A mobile aeraulic isolation device  1   c  of this third embodiment is shown: in closed global position, so-called floor movement position M in  FIG. 21 , and in open global position so-called fixed in-use position U covering a hospital bed  191  in  FIG. 22 . 
   It is seen that the aeraulic isolation device  1   c  of this third variant identically reproduces most of the particular aspects described above for the first variant  1   a  of the invention. The common elements are denoted with the same references in drawings  21  to  33   a . It appears unnecessary to repeat their description. 
   The aeraulic isolation device  1   c  comprises relative movement means  10  for the plenums formed of: two hinges  9   a ,  9   b  integral with two abutting edges of plenums  5 , 6 , and pivots  19   a ,  19   b  shown in  FIGS. 25 and 29   b  (whose functioning is described in detail below). They allow the second rigid downstream mobile plenum  6  for air diffusion to be folded relative to the first rigid air diffusing upstream plenum  5  of diffuser  4 . Therefore the second rigid mobile downstream plenum  6  can be folded relative to chassis  12  and in at least two distinct relative positions, one so-called fixed in-use position U shown in  FIG. 22  and the other so-called movement position M over floor  15  shown in  FIG. 21 . 
   With reference to  FIGS. 26   a  and  26   b  it is seen that the two rigid plenums  5 , 6  are formed of diffusing caissons  71 , 72 , 73  delimited by side surfaces  51   a/b/c/d ,  52   a/b/c/d ,  53   a/b/c/d  that are independent (do not directly communicate)so as to delimit two inner volumes  68 , 69  of disjoined plenums  5 , 6 . In the particular case described, the downstream plenum  6  is itself formed of two diffusing caissons (as described below). This increases the number of side surfaces of downstream plenum  6 . But it will be understood that the downstream plenum  6  formed of its two caissons  72 , 73  is entirely closed, disjoined and non-communicating with the upstream plenum  5  itself formed of caisson  71 . This arrangement in multiple caissons recommended by the invention increases the homogeneity of the airflow and enables modulated flow adjustment between the different areas. 
   In the variant of the invention shown in the drawings and recommended by the invention, the first rigid upstream plenum  5  and the second rigid downstream plenum diffusing air are both mobile and adjustable relative to chassis  12  in two distinct relative positions. 
   In fixed in-use position U above bed  191  shown in  FIG. 22 , the first mobile diffusing surface of the first upstream plenum  5  and the second diffusing surface  8  of the second downstream plenum  6  are horizontal and positioned facing the floor at a distance from it. In this in-use position the airflow F passes through the two diffusing surfaces  7 , 8  in a substantially vertical air direction zz′ and entirely covers the sensitive area  2 . It is seen that in this in-use position the projection surface PUl over floor  15  of the first mobile diffusing surface  7  and the projection surface PU 2  over floor  15  of the second mobile diffusing surface  8  have a maximum size of LU 1 ,LU 2 . 
   In the other floor movement position M shown in FIGS.  21 , 27   b , the floor projection surface PM 1  of the first mobile diffusing surface  7  of the first mobile plenum  5  and floor projection PM 2  of the second mobile diffusing surface of the second mobile plenum  6  are zero and are therefore of minimum size LM 1 ,LM 2 . The two diffusing surfaces  7 , 8  are vertical. 
   Relative movement means  10  formed of two hinges  9   a ,  9   b  and pivots  19   a ,  19   b  shown in  FIGS. 25 and 29   b  enable movement of the first  5  and second  6  rigid diffusion plenums both relative to chassis  12  and relative to one another. 
   Physical air decontamination means  20  of moving air crossing through them ensure decontamination of airborne aerosols. In the variant shown, air pressurizing means  25  are seen,  FIG. 33   b , formed of a fan  25  fitted to each of physical decontamination means  20 . 
   Also, aeraulic connection  30  and air circulation means aeraulically connect air pressurizing means  25 , physical air decontamination means  20  and the two rigid air diffusing plenums  5 , 6  of air diffuser  4 . They force the airflow F to pass through the porous air diffusing surfaces  7 , 8 . 
     FIG. 24  shows a mobile supporting chassis  12  bearing the entire mobile aeraulic isolation device  1   c . It is mechanically connected to the two rigid plenums  5 , 6  of air diffuser  4 , to the physical air decontamination means  20 , to the air pressurizing means  25  and to the aeraulic connection means  30 . It is provided with horizontal movement means  40  for chassis  12  relative to the floor, formed of casters ( 141  . 148 ). 
   With reference to  FIG. 25  it is seen that the relative movement means  10  is made up of two rotation axes  11   a ,  11   b  formed by two hinges  9   a ,  9   b  cooperating with two pivots  19   a ,  19   b  shown  FIG. 29   b . The plenum rotation axis  11   a  substantiated by hinges  9   a ,  9   b  allows rigid plenums  5 , 6  to move relative to one another. The rotation axis  11   b  relative to the frame substantiated by pivots  19   a ,  19   b  allows rotation of both rigid plenums  5 , 6  relative to frame  12 . 
   With reference to  FIGS. 21 and 25 , it is seen that the two rotation axes  11   a ,  11   b  of rigid plenums  5 , 6  are positioned horizontally relative to floor  15 . Also, in the so-called floor movement position M shown in  FIGS. 21 and 25  both rigid plenums  5 , 6  are hinge folded around plenum rotation axis  11   a  so that the first mobile diffusing surface  7  of the first mobile upstream plenum  5  is facing and is opposite the second mobile diffusing surface  8  of the second mobile downstream plenum  6 . 
   Horizontal sliding means  13  of rotation axis  11   b  of plenums  5 , 6  relative to frame  12  are fitted to device  1   c . They are formed of two extendable horizontal slide rails  14   a ,  14   b  of “drawer” type integral with the chassis and positioned in its upper part. The two pivots  19   a ,  19   b  slide horizontally on rollers along and between the two slide rails  14   a ,  14   b.    
   In floor movement (or closed) position M shown in  FIGS. 21 and 25 , the two rigid plenums  5 , 6  are fodled relative to hinges  9   a ,  9   b  so that the first mobile diffusing surface  7  of the first mobile upstream plenum  5  faces and is opposite the second mobile diffusing surface  8  of the second mobile downstream plenum  6 . 
   With reference to  FIGS. 23 and 24  it is seen that the horizontal sliding means  13  of rotation axes  11   a ,  11   b  of rigid plenums  5 , 6  between themselves and relative to chassis  12  comprise two extreme sliding positions. In in-use position U shownn in  FIG. 23 , the first mobile diffusing surface  7  of the first upstream plenum  5  and the second mobile diffusing surface  8  of the second downstream plenum  6  are horizontal. Rotation axes  11   a ,  11   b  of rigid plenums  5 , 6  are in so-called forward position. So that plenums  5 , 6  are away from the so-called rear portion  16  of chassis  12  that is the furthest from the centre of sensitive area  2 . In floor move position M shown  FIG. 24  the first mobile diffusing surface  7  of the first mobile upstream  5  faces and is opposite the second mobile diffusing surface  8  of the second mobile downstream plenum  6 . The two diffusing surfaces  7 , 8  are vertical. Rotation axes  11   a ,  11   b  of rigid plenums  5 , 6  are in so-called near-rear position close to the so-called rear portion  16  of chassis  12 . So that plenums  5 , 6  are close to the so-called rear portion of chassis  12  the furthest away from the centre of sensitive area  2 . 
   With reference to  FIGS. 28   d ,  29   b  and  32  it is seen that device  1   c  comprises mobile releasable interlocking means  17  for rigid plenums  5 , 6  in aligned in-use position U so that the first and second diffusing surfaces  7 , 8  of plenums  5 , 6  are coplanar. These mobile releasable interlocking means  17  are integral with the two side frame parts  31 , 32  supporting the two plenums and therefore with the two sliding pivots  19   a ,  19   b . So that the mobile releasable interlocking means  17  are mobile during horizontal sliding of said rotation axis  11   b  of rigid plenums  5 , 6  relative to chassis  12 . 
   Referring to  FIG. 29   a , it is seen that device  1   c  comprises releasable locking means  18  to chassis  12  for frame part  31  which bears mobile plenum  5  and is closest to the so-called rear portion  16  of chassis  12 , when in aligned in-use position U. So that in in-use position U the diffusing surface  7  is horizontal and fixed relative to chassis  12 . On account of prior activation of mobile releasable interlocking means  17 , the diffusing surface  8  is also fixed in horizontal position relative to chassis  12 . 
     FIGS. 21 ,  24 ,  25 ,  26   a ,  26   b ,  27   a ,  29   b  and  31  show means  210  to aid extension of plenums  5 , 6  recommended by the invention. They are formed of tensioning means, springs in particular  211   a ,  211   b , positioned above plenums  5 , 6  housed in casings  212   a ,  212   b  themselves fixed at their base and maintained in position by collars  213  on frames  31 , 32  of plenums  5 , 6 . Springs  211   a ,  211   b  are taut when device  1   c  is in floor movement position M and released in fixed in-use position U. 
   Their bending at hinge  10  is guided by shaped parts  230   a ,  230   b  described below. Retraction of springs  211   a ,  211   b  offsets the weight of plenums  5 , 6  and aids their extension until they reach their coplanar in-use position U. 
   Shown in transparency in  FIG. 30   b  are adjustment means  220  for the height of plenums  5 , 6  recommended by the invention. Each of the two vertical side posts of chassis  12  is similar.  FIGS. 30   b  and  31  describe the right post  221 . It is formed of two hollow coaxial telescopic uprights  221   a ,  221   b  which fit into one another by vertical translation. Inside uprights  221   a ,  221   b  is a pressure-tared jack  22  to offset the weight of the height-adjustable mobile assembly, and a wedge-block  223  integral with the upper upright  221   b  ensuring size adjustment for jack installation, jack  22  itself being integral with lower upright  221   a . Uprights  221   a ,  221   b  have lower height adjustment via position stop  224  and upper adjustment via the stroke of jack  222 . A range of holes  225  with pegs  226  ensures the maintaining and adjustment of height position for plenums  5 , 6 . 
     FIGS. 24 ,  25 ,  26   a ,  26   b ,  27   a  show bending means both for the tubes of aeraulic connection means  30  and for springs  211   a ,  211   b  when device  1   c  is in floor movement position M. They are formed of quarter-circle shaped parts  230   a ,  230   b  integral with frames  31 , 32  of plenums  5 , 6  and on which they bend during folding. These shaped parts provide the tubes of aeraulic connection means  30  with sufficient curve radius so that they are not excessively deformed when in floor movement position M. 
   In  FIGS. 26   a ,  26   b ,  27   a ,  32  the truncated pyramid shape can be seen of diffuser caissons  71 , 72 , 73 . This provides improved dispersion of airflow F while enabling the installation of shaped parts  230   a ,  230   b  between plenums  5 , 6 .  FIGS. 26   a ,  26   b ,  27   a  and  32  show the aeraulic connection  30  and air circulation means which comprise a plurality of aeraulic lines  101 , 102 , 103 . 
   With reference to  FIGS. 23 ,  25 ,  26   b ,  27   a ,  33 A it is seen that each aeraulic line is connected (directly or indirectly) by a first end  104 , 105 , 106  to one of physical air decontamination means  21 , 22 , 23 . Each aeraulic line  101 ,  102 ,  103  has a mobile portion  111 , 112 , 113  relative to chassis  12 . And each aeraulic line  101 , 102 , 103  is connected via a second end  107 , 108 , 109  to one of mobile plenums  5 , 6 . 
     FIGS. 26   a ,  26   b  show that the first  5  and second  6  rigid air-diffusing plenum are each formed of a group G 1 ,G 2  of at least one closed, air-distribution diffusing caisson  71 , 72 , 73 . The front plenum  5  is formed of one diffusing caisson  71 . Downstream plenum  6  is formed of two caissons  72 , 73 . Each closed diffusing caisson  71 , 72 , 73  has a so-called diffusing surface  7 , 8   a ,  8   b  covered by a wall in diffusing material  81 , 82 , 83  porous to air. As shown in detail in  FIG. 32 , each caisson  71 , 72 , 73  has another so-called supply surface  85 , 86 , 87  each fitted with an air intake collar  91 , 92 , 93 . The other (side) surfaces  53   a/b/c/d  . . . of caissons  73  . . . are solid. The diffusing caissons  72 , 73  of the first rigid plenum  6  are mobile relative to supporting chassis  12  and to caissons  71  of the second rigid plenum  5  via relative movement means  10  and pivots  19   a/b.    
     FIG. 32  shows that device  1   c  comprises three physical decontamination means  21 , 22 , 23  aeraulically independent. Aeraulic connection means  30  comprise three independent networks of aeraulic lines  101 , 102 , 103  each connecting one physical decontamination means  21 , 22 , 23  to one of mobile plenums  5 , 6 . 
     FIG. 33   a  shows that device  1   c  comprises means  121  for horizontal movement of physical decontamination means  21 , 22 , 23  relative to supporting chassis  12 . These are formed of two slide rails  122 , 123  that are horizontal and integral with chassis  12  on which a mobile frame  124  slides horizontally. Physical decontamination means  21 , 22 , 23  are positioned on and fixed onto mobile frame  124 . 
   It is seen that horizontal movement means  121  for physical decontamination means  21 , 22 , 23  relative to supporting chassis  12  have two extreme positions. In in-use position U shown in  FIGS. 22 ,  23 ,  28   c ,  28   d ,  31 ,  32  and  33  physical decontamination means  21 , 22 , 23  are recessed relative to centre of gravity CU of the mobile isolation device  1   c . On the contrary, in floor movement position M shown in  FIGS. 21 ,  24 ,  25 ,  27   a ,  28   a  and  30   a  the physical decontamination means are brought forward in direction of the centre of gravity CM of mobile isolation device  1   c . This makes it possible to increase the stability of device  1   c  in in-use position U, while reducing required floor space in floor movement position M. It is also seen in  FIGS. 28   a ,  28   b ,  28   c ,  28   d ,  28   e ,  28   f  that aeraulic connection means  30  have modified geometry GU,GM during extension of plenums  5 , 6  between floor movement position M and in-use position U. 
     FIGS. 30   a ,  31 ,  32  show that mobile supporting chassis  12  comprises a lower mobile trolley  125  that is fork-shaped  126 . It is formed of two horizontal, parallel supporting arms  127 , 128  distant from one another. The supporting arms  127 , 128  of chassis  12  are formed of several horizontal portions  131 , 132 , 133 , 134 , 135 , 136  connected together and mobile relative to one another. In the version recommended by the invention shown in  FIGS. 30   a ,  31 ,  32  the lower mobile trolley  125  in fork shape  126  comprises two supporting arms  127 , 128  each formed of several horizontal portions  131 , 132 , 133 , 134 , 135 , 136  connected together and can slide relative to one another along a horizontal axis x,x′. In another variant, not shown, the lower mobile trolley  125  in fork shape  126  could be fitted with two arms  127 , 128  each formed of several horizontal portions  131 , 132 , 133 , 134 , 135 , 136  connected together and pivoting relative to one another along a vertical axis of vertical rotation z,z′. 
   In  FIGS. 30   a ,  31 ,  32  it is seen that lower mobile trolley  125  in fork shape  126  comprises arms  127 , 128  of which each of horizontal portions  131 , 132 , 133 , 134 , 135 , 136  comprises at least one wheel  141 , 142 , 143 , 144 , 145 , 146 , 147 , 148  with a horizonal rotation axis r,r′. These rotation axes r,r′ of the wheels preferably pivot horizontally to facilitate multidirectional movements of device  1   c  over the floor  15  in floor movement position M. 
   With reference to  FIGS. 22 ,  23 ,  28   d ,  28   f  it is seen that mobile aeraulic isolation device  1   c  comprises vertical channelling means  150  for airflow for in-use position U comprising curtains  151 , 152 , 153  . . .  156  surrounding sensitive area  2  on its four sides. It is seen that curtains  151 , 12 , 153  . . .  156  shown are both mobile relative to chassis  12  during movement between in-use position U and floor movement position M since they are fixed by their upper part around the edge of the two frame portions  31 , 32  supporting the two plenums  5 , 6 . But they are also mobile relative to at least mobile plenum  5  when they are opened up on the edge of plenums  5 , 6  particularly in in-use position U. In the configuration shown in  FIGS. 26   a ,  26   b  the vertical channelling means  150  for airflow are formed of curtains  151 , 152 , 152  . . .  156  with winders  161 , 162 , 163 , 164 , 165 , 166  whose winder axes er 1 , er 2 , er 3 , er 4 ,er 5  er 6  are positioned at the lower part  167  and on the periphery P of air diffusing plenums  5 , 6 . 
   In another variant (not shown) vertical channelling means  150  for airflow may be formed of curtains sliding on a rail positioned at the lower part  167  and on periphery P of air diffuser plenums  5 , 6 . 
   In a further variant (not shown) these channelling curtains comprise a plurality of abutting parallel strips. This facilitates hand access for medical staff to attend a patient in the bed protected by the system  1   c.    
   In another variant (not shown) vertical channelling means  150  for airflow also comprise a combination of: detection means (of movement of persons and/or increase in contamination)—and activation means for the level (and/or position relative to plenums) of vertical channelling means  150  of airflow in relation to the measurement taken by the detection means. This makes it possible only to activate the air channelling means, in particular to lower or slide the curtains into active position, when a visitor is present or when there is movement inside the room which risks increasing contamination. 
     FIG. 22  shows an aeraulically decontaminated bed  190  formed of the combination between: a hospital bed  191 —and a mobile aeraulic isolation device  1   c  such as described above. The two rigid air diffusing plenums  5 , 6  can be seen, mechanically connected to one another and mobile relative to one another. They each have a planar, air-porous air diffusing surface  7 , 8  in fixed, open in-use position U. The diffusing surfaces  7 , 8  are coplanar, horizontal and positioned facing the upper part of bed  191  and away from it so as to diffuse an airflow F crossing through them in an air direction zz′ substantially perpendicular to mattress  192  of bed  191 . As described above, aeraulically decontaminated bed  190  is remarkable in that its rigid plenums  5 , 6  are delimited by independent side surfaces  51   a/b/c/d ,  52   a/b/c/d ,  53   a/b/c/d  (do not communicate directly) so as to delimit at least two inner disjoined plenum volumes  68 , 69 . 
   In the configuration recommended by the invention, it is seen in  FIGS. 22 and 33   a  that the physical air decontamination means  20 , 21 , 22 , 23  have an air intake  194 , 195 , 196  located at the foot end  197  of bed  191  and in its lower part  198 . This arrangement improves the aeraulics of air movement and reduces turbulence. Air moves vertically over the bed, enters vertically under the bed via its two sides and is then channelled under the bed in direction of air intakes  194 , 195 , 196 . The mobile chassis  12  of mobile aeraulic isolation device  1   c  and its decontamination means  20 , 21 , 22 , 23  are arranged at the foot end  197  of bed  191 . The second mobile rigid downstream plenum the furthest from chassis  12  is positioned at the head end  199  of bed  191 . 
     FIG. 33   b  is a schematic diagram of a recommended example of configuration of physical decontamination means  20 . Thy are contained inside a metal parallelepiped envelope  200 . The air derived from foot end  197  of bed  191  enters via an air intake  194  fitted with a coarse disposable pre-filter  201 . The coarse pre-filter  201  is intended to block large particles, “fluff”, textile dust . . . which may be present under bed  191 . The air then passes through an inlet noise muffler  202 , then an electric fan  25 , an outlet noise muffler  203  and finally through air sterilisation reactor  204  before reaching the outlet collar  205  which is connected to one of aeraulic lines  101  supplying one of the plenums. 
   Preferably, the invention recommends using a sterilisation reactor of the type described in patent U.S. Pat. No. 5,474,600 “apparatus for biological purification and filtration of air”. Preferably a device for amplifying electrostatic fields will be used of the type described in French patent application FR 99 14899 and an ionic emission device of the type described in French patent application FR 00 16607. 
     FIGS. 28   a  to  28   f  describe the opening sequence of device  1   c  from its floor movement position M to its fixed in-use position U.  FIG. 28   a  shows the device  1   c  in floor movement position M close to a hospital bed  191 .  FIG. 28   b  describes the opening along axis x,x′ of horizontal portions  131 ,  136 ) of the two supporting arms  127 , 128  of chassis  12 , the unlocking of means  171  maintaining plenums  5 , 6  in folded position relative to chassis  12 , the forward horizontal movement of both plenums  5 , 6  via the two slide rails  14   a ,  14   b .  FIG. 28   c  shows unlocking of means  172  maintaining plenums in folded position then the rotation of upstream plenum  5  along axis  11   b  of pivots  19   a ,  19   b  as far as the stop position and locking of means  18  relative to chassis  12 , and finally the rear positioning of decontamination means  21 , 22 , 23 .  FIG. 28   d  shows the rotation of downstream plenum  6  along axis  11   a  of hinges  9   a ,  9   b , hood raised to access handling means  175 , as far as its locking into position by means  17  relative to the upstream plenum  5 .  FIG. 28   e , plenums  5 , 6  reach their height of use U by unlocking the vertical translation of uprights  221   a ,  221   b  using pegs  226 , the chassis handling means  176  facilitate adjustment at desired height then pegs  226  associated with holes  225  ensure the maintaining in in-use position. Finally,  FIG. 28   f  shows the device  1   c  in in-use position U provided with channelling means  150  for airflow over an aeraulically decontaminated bed  190 . 
   Subject and Industrial Applications of the Invention 
   On the basis of the described invention, the applicants have developed a mobile protective isolation device for immunocompromised and/or fragile persons called ImmunAIR™. This device is equipped with 4 physical decontamination means of the type described above. When in in-use position U, it can cover and protect a hospital bed with a size of: length 2.4 m, width: 1.05 m by means of a uniform sterilised vertical airflow at low speed 640 m 3 /hour, i.e. approximately 210 sterilised air changes per hour within the 3 m 3  of isolator covering the bed. In the room of an immunocompromised patient occupying the bed, it can also generate a vertical airflow of 640 m 3 /hour ensuring 25 sterilised air changes per hour in the room. It forms a “mobile sterile room” which can be set up or taken down in less than 10 minutes. 
   In folded floor movement position M, its vertical cross size is: width 0.760 m and height 1.98 m. So that the device can easily be passed through a doorway of standard size: width 0.8 m and height less than 2 m. 
   By means of the so-called PLASMER sterilisation technique described above, the aeraulic load loss is approximately 250 Pascals and the noise level is 43 DB. It ensures destruction of mycoses, bacteria, spores and viruses in the room. 
   Tests in hospital rooms, initially with massive contamination (&gt;300 cfu/m 3  bacteria and 285 cfu/m 3  in fungi) have shown complete biodecontamination under the airflow for total flora (bacteria) and fungi in less than 20 minutes. Repeated measurements under the flow for several hours have shown stability over time of absolute decontamination at less than 1 cfu/m 3 . In a room with average contamination (29 cfu/m 3  total flora and 38 cfu/m 3  fungi) room decontamination was ascertained (outside the flow) in less than 20 minutes to reach stabilised contamination values of less than 4 cfu/m 3  total flora and &lt;2 cfu/m 3  fungi. 
   In a hospital environment, the device can substitute for laminar flow rooms for the protective isolation of weakened or immunosuppressed patients. It can also, for an investment that is approximately 4 times less and operating costs that are 5 to 10 times less, substitute for laminar flow clean rooms to provide protective isolation equipment in: district hospitals, clinics and functional rehabilitation centres for immunosuppressed patents. Finally it can be used for early home discharge of immunosuppressed or aplasic patients. 
   The applications of the protective isolation device of the invention firstly concern haematology departments for aeraulic protection of patients undergoing bone marrow homografts and in haemopathy cases leading to severe neutropaenia. In oncology departments, it is recommended for patients with solid tumours that are particularly unresponsive and require aggressive chemotherapy or extended high dose corticotherapy. It is of particular use in serious burns departments. Finally, it is recommended in intensive care units, in particular for patients undergoing immunosuppressive treatment for solid organ transplants and patients requiring transient intensive care subsequent to haemopathy with therapeutic aplasia. 
   In the entire above description, particular attention was focused on aseptic isolation of immunosuppressed patients. The airflow in this case is directed from the diffusers towards the area over the bed. It will easily be understood that the invention also adapts to septic isolation of contagious patients by reversing the direction of airflow. 
   Advantages of the Invention 
   One first advantage of the mobile aeraulic isolation device with variable geometry air diffuser and two mobile plenums according to the invention is that it can be used to form a mobile room with absolute sterility, that can be provisionally installed inside a patient&#39;s room and folded up into a size enabling it to pass through a standard doorway approximately 205 cm high and 80 cm wide, i.e. approximately 81 inches×31 inches. This means that the device of the invention can be used for home medical care, especially to treat immunosuppressed patients at home. 
   A second advantage of the device of the invention is that the effective width of the plenums it uses is not limited by the width of doors through which it must pass through. So that the volume of protection surrounding the patient is not itself limited. This is beneficial to patient comfort and protection. 
   A third advantage of the device of the invention is that it leaves the head of the patient&#39;s bed entirely free and in no way hinders the positioning of medical technical equipment placed at the top of the bed (monitoring devices, resuscitation devices, gas outlets . . . ) 
   A fourth advantage of the device is that it provides greater stability when in use. 
   A fifth advantage of the device is that its mobile geometry can offset displacement of the centre of gravity to the free end of the device when the two plenums are joined in in-use position, to increase its stability. 
   A sixth advantage of the device is that by means of its mobile accessory curtains it can improve air pressure over the bed and accelerate evacuation of parasite contamination. They stop the penetration into the sensitive bed area of Pflügge droplets emitted by visitors or attending staff when speaking, coughing or sneezing. They facilitate visitor and personnel accesses to the bedside of highly immunosuppressed patients. 
   A seventh advantage of the device is that its aeraulic design makes it less noisy and less energy-consuming. 
   An eight advantage is to enable mobility through any doorway or window and hence great adaptability from one hospital room to another and/or from one hospitalised patient&#39;s home to another. So that it ensures greater capacity of use and better amortization of operational costs. 
   A ninth and chief advantage of the invention is that, in closed floor movement position, the size of the device is much smaller than that of devices of the prior art which can cover and protect a bed. This provides better mobility. 
   The scope of the invention is to be considered more in relation to the following claims and their legal equivalents than to the examples given above.