Dual breathable gas supply apparatus

Abstract

Breathable gas supply apparatus (1), for connecting with a diving face mask or helmet (100), the gas supply apparatus (1) is connectable with a rebreather or reclaim unit (5) for a first supply of breathable gas (2) for closed-circuit use, and connectable with a second supply of breathable gas (3) for open-circuit use, wherein the apparatus (1) comprises valve means (6) for: a) sealing or opening supply (2) from said rebreather or reclaim unit (5); and b) opening or sealing supply from said second supply of breathable gas (3); wherein, the apparatus (1) is configured such that sealing supply (2) from said rebreather or reclaim unit (5) corresponds to opening supply (3) from said second supply of breathable gas, and vice-versa, enabling switching between two sources of breathable gas without interruption in supply.

Description

[0001] Dual Breathable Gas Supply Apparatus

[0002] The present invention relates to a breathable gas supply apparatus for connecting with a diving face mask or helmet. In particular, the invention relates to a breathable gas supply apparatus connectable with a first and second supply of breathable gas.

[0003] A full-face mask or helmet is usually supplied with breathable gas from a compressed gas cylinder or other external supply (i.e. from the surface or a habitat) through a demand valve I regulator. No bite mouthpiece is required. This is typically termed open-circuit. Rebreather technology uses a closed-circuit principle, and the two technologies are both different and not readily combined in a full-face mask or helmet.

[0004] For instance, replacement of an open-circuit regulator with a rebreather results in flow restrictions and bi-directional flow in various parts of the apparatus, leading to restriction of breathing and build-up of carbon dioxide. Rebreathers rely on wide passages as one’s breathing is the only driving force, whereas open-circuit systems use compressed gas and, thus, the standard masks are provided with narrow flow passages unsuitable for rebreather use. Typically a rebreather used with a full-face mask still requires a bite mouthpiece, to prevent flooding the rebreather in the case of water ingress, and to prevent mixing of fresh and exhaled gas in the mask cavity, worsening the above problems.

[0005] Although the two technologies are known and one might theoretically think of combining them, it is reiterated that the technologies are different and not readily combined, unless various problems are addressed and solved through inventive insight. For example, if one did combine the technologies this brings with it the serious disadvantage of excessive protrusion of the apparatus from the head, generating torque, which resists head movement and, potentially, displaces the seal in the case of a full-face mask. Further, this increased “dead space” in which fresh and exhaled gas may mix, and this risk of leakage, means that the rebreather still requires a bite mouthpiece, and this removes the normal advantage of using a full face mask which allows easy communication as one can readily talk, and unrestricted breathing as one can fully open the mouth.

[0006] It is well know that a bite mouthpiece obstructs speech and also provides breathing resistance. The present invention is aimed at solving these and other problems associated with the prior art, or simple combinations thereof.

[0007] According to a first aspect, the present invention provides breathable gas supply apparatus, for connecting with a diving face mask or helmet, the gas supply apparatus is connectable with a rebreather or reclaim unit for a first supply of breathable gas for closed-circuit use, and connectable with a second supply of breathable gas for open-circuit use, wherein the apparatus comprises first valve means configured for: a) sealing or opening supply from said rebreather or reclaim unit; and b) opening or sealing supply from said second supply of breathable gas; wherein, the apparatus is configured such that sealing supply from said rebreather or reclaim unit corresponds to opening supply from said second supply of breathable gas, and vice-versa, enabling switching between two sources of breathable gas without interruption in supply.

[0008] Preferably, the first valve means is configured to be movable between: a first condition in which said diving face mask or helmet is provided in fluid communication with a first supply of breathable gas for closed-circuit use; and a second condition in which said diving face mask or helmet is provided in fluid communication with a second supply of breathable gas for open-circuit use.

[0009] Preferably, the first valve means is configured for: c) opening or sealing supply of gas to an open circuit exhaust valve.

[0010] Preferably, a first switch block comprises the first valve means, a demand valve and an exhaust valve.

[0011] Preferably, when the first valve means is in a first condition, a / the first switch block comprises a rebreather or reclaim unit supply passageway, which is interruptible by the first valve means.

[0012] Preferably, when the first valve means is in a second condition, a / the first switch block comprises a second supply passageway, which is interruptible by the first valve means.

[0013] Preferably, in the second condition, the second supply passageway is configured to be in fluid communication with a / the demand valve and / or an / the exhaust valve. Preferably, the apparatus further comprising a second valve means configured for sealing or opening supply of gas to said rebreather or reclaim unit.

[0014] Preferably, a second switch block comprises the second valve means.

[0015] Preferably, the first and / or second valve means is / are located at side region(s) of the diving face mask or helmet, being configured to minimise protrusion in front of a user's mouth.

[0016] Preferably, the apparatus further comprising a support bar for connecting first and second switch blocks, being configured to reduce torque applied to said diving face mask or helmet during switching supply.

[0017] Preferably, the apparatus further comprising one or more support brackets, extending from the support bar to said diving face mask or helmet, providing additional torque resistance during switching supply.

[0018] Preferably, the first and / or second switch block comprises a hand moveable member (handle or otherwise) for manually opening and / or closing its respective valve means.

[0019] Alternatively, the first and / or second switch block comprises an actuator, operable electronically, for automatically opening and / or closing its respective valve means.

[0020] Preferably, the apparatus is configured to prevent supply of breathable gas from both said rebreather and said second supply of breathable gas at the same time. In that context opening of the rebreather or reclaim unit supply passageway closes the supply passageway from the second supply of breathable gas.

[0021] Preferably, the apparatus comprises an over pressure and / or manual purge button or tab.

[0022] Preferably, the second supply of breathable gas is a compressed source of breathable gas.

[0023] Preferably, the invention provides an interface between a diving rebreather or other breathing gas reclamation unit, an open-circuit gas supply, and a helmet or fullface mask.

[0024] Preferably the apparatus comprises a support bar connecting both switch blocks to each other to prevent / reduce torque when switching between OC (open circuit) and CCR (closed circuit rebreather).

[0025] Preferably the apparatus comprises support brackets from the support bar to the Mask / Helmet to prevent / reduce torque when switching between OC and CCR. Preferably, the first valve means is configured to be connectable to an auxiliary port of said face mask or helmet.

[0026] Preferably, the first and second switch blocks are configured to be located to one or more side regions of the / said face mask I helmet, to reduce torque in use.

[0027] Preferably, the apparatus further comprises a surface air valve, communications apparatus and / or drinking I feeding apparatus.

[0028] According to a second aspect, the present invention provides a method for switching between two sources of breathable gas without interruption in supply, the method comprising: an apparatus according to the first aspect; wherein the method further comprising: rotating or actuating a moveable member of the first valve means and, thereby: a) sealing or opening supply from a rebreather or reclaim unit; and b) opening or sealing supply from a second supply of breathable gas.

[0029] Preferably, the method comprising rotating or actuating a moveable member of the first valve means and, thereby: c) opening or sealing supply of gas to an open circuit exhaust.

[0030] Preferably, the method comprising rotating or actuating a moveable member of the second valve mean and, thereby: d) sealing or opening supply of gas to the rebreather or reclaim unit.

[0031] Preferably, the method comprising simultaneous rotation or actuation of moveable members of the first and second valve means.

[0032] According to a third aspect, the present invention provides a breathable gas supply apparatus connected with a diving face mask or helmet, the gas supply apparatus being connect with a rebreather or reclaim unit for a first supply of breathable gas for closed-circuit use, and connected with a second supply of breathable gas for open-circuit use, wherein the apparatus comprises first valve means configured for: a) sealing or opening supply from the rebreather or reclaim unit; and b) opening or sealing supply from the second supply of breathable gas; wherein, the apparatus is configured such that sealing supply from the rebreather or reclaim unit corresponds to opening supply from the second supply of breathable gas, and vice-versa, enabling switching between two sources of breathable gas without interruption in supply.

[0033] Preferably, the apparatus further comprises one or more apparatus features of the first aspect.

[0034] Preferably, the apparatus comprises an oronasal mask comprising one or more passageways connectable with said rebreather or reclaim unit for directly supplying gas to or directly exiting gas from the oronasal mask.

[0035] Most preferably, the oronasal mask comprises two separate passageways, one for supplying breathable gas from said rebreather or reclaim unit, the other for exiting exhaled gas to said rebreather or reclaim unit.

[0036] According to a fourth aspect, the present invention provides use of a breathable gas supply apparatus comprising a valve means with a diving face mask or helmet, the gas supply apparatus being connected with a rebreather or reclaim unit for a first supply of breathable gas for closed-circuit use, and connected with a second supply of breathable gas for open-circuit use, wherein the use comprises: a) sealing or opening supply from the rebreather or reclaim unit; and b) opening or sealing supply from the second supply of breathable gas; wherein, sealing supply from the rebreather or reclaim unit corresponds to opening supply from the second supply of breathable gas, and vice-versa, enabling switching between two sources of breathable gas without interruption in supply.

[0037] Preferably, the use comprises a breathable gas supply apparatus according to the first aspect.

[0038] Preferably, the one or more valve means and face mask I helmet are so configured as to locate the one or more valve means to one or more side regions of the face mask I helmet, to reduce torque in use.

[0039] Advantageously, the proposed invention: allows previously non-adapted full-face masks or helmets to be used with a diving rebreather or other breathing gas reclamation unit; minimises the ‘dead space’ for a user; switches between rebreather and alternate supplies of compressed gas; reduces risk of drowning by enabling rebreather divers to use a full-face mask / helmet; enables surface communications and supply of liquids to a rebreather diver; retains mono-directional flow and a wide gas path, eliminating problems; retains both open- and closed-circuit functions, enabling rebreather to be sealed and alternate breathing means to be used, enabling safe donning and doffing on land or underwater, as well as switching between gas supplies; complete functionality of both a rebreather and full-face mask or helmet are retained; rebreather use is still possible even if full-face mask becomes flooded; use of auxiliary ports for location of hose entry points provides low dead space and low breathing resistance for rebreather; and flow can occur in either direction, subject to valves, being clockwise or anti-clockwise around a breathing loop for use with different rebreathers. Advantageously, the invention maintains a low profile, minimizing 'dead space' and reducing interference with head movement.

[0040] As the valve means is / are operable by a single rotational movement of a handle, it enables intuitive switching between breathable gas supplies.

[0041] Advantageously, the addition of a support bar connecting the two switch blocks reduces torque applied to the diving face mask or helmet during switching. Further advantageously, the addition of support brackets, extending from the support bar to the diving face mask or helmet, provides additional torque resistance.

[0042] Advantageously, locating or positioning of the valve means I switch blocks at the sides of the mask I helmet provides a balanced weight distribution, reducing torque in use.

[0043] The following advantages are also perceived, with specific reference to a standard rebreather, and are as follows: reduced breathing resistance owing to absence of a bite mouthpiece - especially important at depth where the breathing gas is dense; reduced strain on the user’s respiratory system - less risk of discomfort and pulmonary oedema that is a known complication of deep diving and rebreather use; enables high workload at depth by permitting ventilation of large volumes of gas with low effort; reduced pressure swing in the mask I helmet cavity reduces leakage; clear communications - absence of a bite mouthpiece removes interference with speaking process; no bubble noise, no noise of open-circuit gas injection; direct speech possible at close range; ports for microphones and communications units; reduced carbon dioxide build-up I re-inhalation - reduced bidirectional flow preventing exhaled gas (in particular end-respiratory gas, containing a high percentage of CO2) being re-inhaled by the user (a problem worsened by breathing resistance leading to shallow breaths and the risk of CO2 poisoning and respiratory failure); location of breathing hose connectors on opposite sides of the mask creates unidirectional flow, coupled with low oronasal volume and unrestricted ventilation; prevention of liquid build-up - location of hose connectors on sides reduces possibility of water entering the rebreather / reclaim unit and aids any required removal; absence of a bite mouthpiece removes the problem of the user’s saliva entering the system; retention of the function of a standard exhaust valve enables easy ejection of liquid from the mask; improved comfort - location of breathing hose attachments exerts minimum torque on mask I helmet and the user’s head and neck in use, unlike long lever arm of known units which create discomfort and leakage; superior comfort to mouthpiece-type breathing systems; hose location balances weight distribution of the mask allowing free head movement; improved safety - no risk of drowning owing to loss of mouthpiece; and immediate access to independent breathing systems in the same unit - improved likelihood of an unconscious diver surviving and being rescued.

[0044] The invention will now be disclosed, by way of example only, with reference to the following drawings, in which: Figure 1 is a schematic drawing of a breathable gas supply apparatus, upon which the embodiment of Figures 2 to 5 is based;

[0045] Figure 2 is a front elevation of a face mask including the breathable gas supply apparatus;

[0046] Figure 3 is a side elevation of the face mask of Figure 2;

[0047] Figures 4a and 4b are side elevations of a first switch block of Figure 2, in respective first and second conditions;

[0048] Figures 5a and 5b are side elevations of a second switch block of Figure 2, in respective first and second conditions;

[0049] Figure 6 is a front elevation of a support bar and side braces I brackets, for mounting a breathable gas supply apparatus of Figures 1 to 5 to a face mask. The invention will be described in relation to a known face mask I helmet 100 which includes auxiliary connection ports 101 ; 102 located at side regions of the mask 100, a transparent view screen 103, and an oronasal mask 106. The face mask 100 includes one or more seals 107 for sealing to a user’s head

[0050] Auxiliary connection ports 101 ; 102 are normally used for a microphone or external breathing port (not shown at those locations). However, in the present invention, auxiliary connection ports 101 ; 102 are repurposed for use as closed- circuit breathing connections. A demand valve 104 typically provides breathable gas from a pressurised gas supply 3. This supply is used only used when the closed- circuit is deactivated or sealed off, for instance on the surface, in the case of a malfunction, or during donning or doffing of the apparatus when the closed-circuit element of the system must be sealed to prevent water ingress, or when unlimited supplies of open-circuit gas are available, for instance when using surface or habitat- supplied gas, where open-circuit gas is used by default and the closed-circuit system is used for emergency purposes. An exhaust valve 105 is provided for ejection of exhaled gas, and an additional over pressure I manual exhaust valve 32 is preferably placed at the base of the mask so as to also eject any liquid or water that may have entered the mask. The view screen 103 enables the user to see his / her surroundings underwater, and the apparatus is sealed to the user’s head or neck with the seal 107.

[0051] The oronasal mask is used to reduce the build-up and re-inhalation of carbon dioxide within the mask or helmet, and to prevent water vapour from the user’s breath condensing on the view screen 103, and within the face mask as a whole. For convenience, Figures 1 through to 6 will all be described together. Figures 1 to 5 show a breathable gas supply apparatus, generally identified by reference 1. Figure 6 shows the optional bracing system.

[0052] The gas supply apparatus 1 includes a rebreather apparatus 2, for closed- circuit use, and a supply of compressed gas 3, for open-circuit use. The rebreather apparatus 2 and supply of compressed gas 3 are independently usable to enable breathing of a user of the apparatus 1 , such that a supply of breathable gas is always available, and the user may switch between the rebreather apparatus 2 and supply of compressed gas 3.

[0053] The supply of compressed gas 3 is supplied with breathable gas from cylinders or tanks or other external source (not shown) which are standard and known in the art, which cylinders I tanks or external source per se do not form part of the invention.

[0054] The rebreather apparatus 2 includes a rebreather / reclaim unit 5 which is capable of receiving exhaust gas from breathing and reprocessing the exhaust gas to provide breathable gas for inhalation by the user. The rebreather I reclaim unit 5 reprocesses the breathing gas by removing carbon dioxide and restoring oxygen content. The rebreather apparatus 2 further includes switch blocks 6; 7 (including first and second valve means, respectively), which are connected to auxiliary ports 101 / 102 of the face mask 100, and have hoses 8; 9 for transferring exhaled gas to the rebreather I reclaim unit 5 and reprocessed breathable gas back to the face mask 100. The rebreather I reclaim unit 5 is standard and known in the art.

[0055] Each switch block 6; 7 includes an internal valve 10a; 10b (being first and second valve means, respectively) and external handles 11a; 11b, respectively, operatively connected to the internal valves 10a; 10b. Each handle 11a; 11 b is operable by rotation from a first condition in which the valve 10a; 10b is open to a second condition in which the valve 10a; 10b is closed, so as to open and close passageways for transmission of exhaust gas I breathable gas to I from the rebreather I reclaim unit 5. In this example, the handles 11a; 11b are rotatable through 180 degrees between first and second conditions - although this is not essential. Each switch block 6; 7 is a manually operated, airtight switching mechanism that enables switching between breathing from the rebreather I reclaim unit 5 and a supply of compressed gas 3. In an alternative, operation of the switch block 6; 7 may be automated, being electronically actuated. With respect to operation of the switch blocks 6; 7 to open and close passageways leading to the rebreather I reclaim unit 5, both operate in a similar way. However, in this example switch block 6 has additional functions - although it could be either switch block if flow through the rebreather was reversed. Switch block 6 additionally comprises the demand valve 104 and exhaust valve 105, as elaborated upon below.

[0056] Each switch block 6; 7 includes a one-way valve 29 at its distal end from the face mask 100, which serves to ensure the correct direction of flow of gas around the rebreather I reclaim unit 5, but is also so located to prevent flooding of the rebreather

[0057] I reclaim unit 5. As shown in Figures 4a; 4b; 5a; 5b, the one-way valve 29 is located between the switch block 6 and the corresponding hose 8 - and switch block 7 and hose 9 are arranged the same way. The one-way valve 29 may be integrated as part of the switch blocks 6; 7, or indeed as part of the hoses 8; 9 but are preferably separate components. By being separate, and easily interchanged or turned around, direction of flow around the closed-circuit can be switched, or one can easily substitute different versions having different connections for use with a variety of different rebreather I reclaim units. These one-way valves 29 are preferentially positioned in a location that will minimize bidirectional flow of gas (and, so, prevent re-inhalation of carbon dioxide), yet also prevent the inadvertent intake of water into the rebreather I reclaim unit 5. The one-way valves 29 are preferably check valves.

[0058] As shown in more detail in Figures 4a and 4b, internal valve 10a includes a valve housing 18, movable valve member 19 and various seals (not shown) I sealing surfaces between the two. The valve member 19 is, essentially, cylindrical but hollowed, and includes a valve aperture 20 formed in a cylindrical side wall of the valve member 19, the position of which can be rotated through rotating handle 11a so as to open and close passageways for gas through the valve 10a. The valve member 19 and valve housing 18 may be sealed by sealing means such as O-rings, or simply by a tight fit, and may optionally contain means to lubricate its surfaces to keep out salt water or other debris. Internal valve 10b (within switch block 7) operates in this context in the same manner as internal valve 10a by rotating handle

[0059] I I b. Switch block 6 is operatively connected to the supply of compressed gas 3. Movable valve member 19 directs the aperture 20 either: towards the rebreather unit 2; or towards the demand-valve 104, lever arm mechanism 104a and exhaust 105 of the supply of open circuit gas 3. Switch block 6 also includes the exhaust 105, making exiting exhaust gas in open circuit use very convenient. Conversely, in closed-circuit use, exhaust valve 105 is disconnected from the breathing system along with open circuit gas supply 3.

[0060] Switch block 6 uniquely houses inlets from the rebreather 5 and from open circuit gas supply 3. Through rotating valve member 19, both inlets and exhaust 105 can be opened I closed at the same. When rebreather 5 is selected, it provides a source of breathable gas to the face mask 100, and open circuit gas supply 3 and exhaust 105 are automatically blocked off. Conversely, hen open circuit gas supply 3 is selected, exhaust 105 is also accessible but rebreather 2 is automatically blocked off.

[0061] As shown in more detail in Figures 5a and 5b, switch block 7 is operatively connected to the supply of rebreather 5. Movable valve member 19 directs the aperture 20 either towards hose 9 of the rebreather system 2 or towards the front of the valve housing 18 of switch block 7, which provides a blank 18a. Switch block 7 includes just an outlet to the rebreather 5 and, so, by rotating valve member 19, only the outlet to the rebreather 5 is accessible. When rebreather 5 is not selected, switch block 7 is blocked and impassable, allowing the demand valve 104 and exhaust valve 105 of switch block 6 to operate correctly.

[0062] The face mask or helmet 100 further includes relocated auxiliary port 30 which may be used for communications and / or drinking / feeding functions. The port 30 if used for communications allows cables for a microphone to pass inside the mask 100, and further may include a push-to-talk button 33 allowing the diver to both talk and listen to communications via a through water communications unit. The invention provides the advantage that speech and verbal messages are uninterrupted by the loud noises associated with open-circuit SCUBA diving, namely the emission of compressed gas through the demand valve, and the escape of bubbles through the exhaust. Thus, far clearer communications are possible. Further, port 30 is configured such that any additional communications and / or drinking I feeding functions are unhindered by operation of the one or more valves.

[0063] The apparatus of the invention may include flexible or rigid hoses, or a combination thereof. In the case of the invention being a full-face mask 100, hoses 8; 9 are preferably flexible to allow movement of the head. Conversely, in the case of the invention being a helmet 100, hoses 8; 9 may be flexible or more rigid as the user may rotate their head within the helmet 100. The position of the external handles 11 a; 11 b may indicate a direction to which the corresponding valve is operative. For example, and as shown in Figures 4a; 4b; 5a; 5b, the elongate part of the handle 11 a and 11 b points towards the rebreather hose 8, indicating closed-circuit use. Whereas, if the handle 11 a and 11 b are rotated 180 degrees to their second condition, the elongate part of the handle 11 a and 11 b points towards the demand valve 104 1 exhaust valve 105, indicating open-circuit use.

[0064] In an alternative, switch blocks 6; 7 may be mounted directly to a face mask or helmet if auxiliary ports are unavailable.

[0065] Figure 6 shows a support bar 200, for securing the switch blocks 6; 7 together. The support bar 200 may be secured to the switch blocks 6; 7 with any durable fastening, for example screws, and may be supplied with appropriate apertures 201 for that purpose. The support bar 200 may also include an aperture 202 for receipt of the manual purge 32.

[0066] Sides braces or brackets 203 may be secured to the support bar 200, for improving torque resistance during switching supply. The braces 203 are securable to a frame of the mask 100 with any durable fastening, and may be supplied with apertures 201 for that purpose.

[0067] In use, switching between closed-circuit use and open-circuit use is easily achieved. Owing to the integration between switch block 6 and the supply of compressed gas 3 - through aperture 20 - and between switch block 6 and the exhaust 105 by simply turning handle 11 a through 180 degrees, a first valve means (valve 10a for the inlet or outlet of the rebreather) is closed and, simultaneously, the connections to the source of compressed gas 3 and exhaust 105 are opened. Further, by simply turning handle 11 b through 180 degrees, the second valve means (valve 10b for the other of the outlet or inlet of the rebreather) is closed. In these conditions of the valves, the user breathes compressed breathable gas from cylinders or external supply (not shown). As each of the handles 11 a; 11 b is conveniently located at a side region of the face mask I helmet 100, each can be easily operated at the same time (simultaneously) by a user’s hands.

[0068] Moreover, switching between open-circuit use and closed circuit use simply involves rotating the handles 11 a; 11 b in an opposite manner. This has the effect of opening both valve means (valves 10a; 10b) which opens hoses 8;9 to the rebreather unit 5, closes the gas path to the demand regulator 104 supplying compressed gas 3, and closes the gas path to the exhaust 105. In these conditions of the valves, the user breathes reprocessed air from the rebreather unit 5.

[0069] It should be noted that the above is the preferred mode of operation, but the operation of the apparatus may be simply adapted to provide additional functionality.

[0070] Those skilled in the art will understand that the direction of movement of gas through the breathable gas supply apparatus 1 may be reversed without significant change to the apparatus 1 . Those skilled in the art will also understand that the operation of the switch blocks 6; 7 may be reversed, such that switch block 7 is operatively connected to one or more of the supply of compressed gas and / or the exhaust.

Claims

Claims:1 .) Breathable gas supply apparatus, for connecting with a diving face mask or helmet, the gas supply apparatus is connectable with a rebreather or reclaim unit for a first supply of breathable gas for closed-circuit use, and connectable with a second supply of breathable gas for open-circuit use, wherein the apparatus comprises first valve means configured for: a) sealing or opening supply from said rebreather or reclaim unit; and b) opening or sealing supply from said second supply of breathable gas; wherein, the apparatus is configured such that sealing supply from said rebreather or reclaim unit corresponds to opening supply from said second supply of breathable gas, and vice-versa, enabling switching between two sources of breathable gas without interruption in supply.2.) The apparatus as claimed in claim 1 , wherein the first valve means is configured to be movable between: a first condition in which said diving face mask or helmet is provided in fluid communication with a first supply of breathable gas for closed-circuit use; and a second condition in which said diving face mask or helmet is provided in fluid communication with a second supply of breathable gas for open-circuit use.3.) The apparatus as claimed in any preceding claim, wherein the first valve means is configured for: c) opening or sealing supply of gas to an open circuit exhaust valve.4.) The apparatus as claimed in any preceding claim, wherein a first switch block comprises the first valve means, a demand valve and an exhaust valve.5.) The apparatus as claimed in any preceding claim, wherein, when the first valve means is in a first condition, a / the first switch block comprises a rebreather or reclaim unit supply passageway, which is interruptible by the first valve means.6.) The apparatus as claimed in any preceding claim, wherein, when the first valve means is in a second condition, a / the first switch block comprises a second supply passageway, which is interruptible by the first valve means.7.) The apparatus as claimed in claim 6, wherein, in the second condition, the second supply passageway is configured to be in fluid communication with a / the demand valve and / or an / the exhaust valve.8.) The apparatus as claimed in any preceding claim further comprising a second valve means configured for sealing or opening supply of gas to said rebreather or reclaim unit.9.) The apparatus as claimed in claim 8, wherein a second switch block comprises the second valve means.10.) The apparatus as claimed in any preceding claim, wherein the first and / or second valve means is / are located at side region(s) of the diving face mask or helmet, being configured to minimise protrusion in front of a user's mouth.11.) The apparatus as claimed in any preceding claim further comprising a support bar for connecting first and second switch blocks, being configured to reduce torque applied to said diving face mask or helmet during switching supply.12.) The apparatus as claimed in claim 10, further comprising one or more support brackets, extending from the support bar to said diving face mask or helmet, providing additional torque resistance during switching supply.13.) The apparatus as claimed in any one of claims 4 to 12, wherein the first and / or second switch block comprises a hand moveable member for manually opening and / or closing its respective valve means.14.) The apparatus as claimed in any one of claims 4 to 12, wherein the first and / or second switch block comprises an actuator, operable electronically, for automatically opening and / or closing its respective valve means.15.) A method for switching between two sources of breathable gas without interruption in supply, the method comprising:an apparatus as claimed in any one of claims 1 to 14; wherein the method further comprising: rotating or actuating a moveable member of the first valve means and, thereby: a) sealing or opening supply from a rebreather or reclaim unit; and b) opening or sealing supply from a second supply of breathable gas.16.) The method as claimed in claim 15 comprising rotating or actuating a moveable member of the first valve means and, thereby: c) opening or sealing supply of gas to an open circuit exhaust.17.) The method as claimed in claim 15 or claim 16 comprising rotating or actuating a moveable member of the second valve mean and, thereby: d) sealing or opening supply of gas to the rebreather or reclaim unit.18.) The method as claimed in any one of claims 15 to 17 comprising simultaneous rotation or actuation of moveable members of the first and second valve means.19.) Breathable gas supply apparatus connected with a diving face mask or helmet, the gas supply apparatus being connect with a rebreather or reclaim unit for a first supply of breathable gas for closed-circuit use, and connected with a second supply of breathable gas for open-circuit use, wherein the apparatus comprises first valve means configured for: a) sealing or opening supply from the rebreather or reclaim unit; and b) opening or sealing supply from the second supply of breathable gas; wherein, the apparatus is configured such that sealing supply from the rebreather or reclaim unit corresponds to opening supply from the second supply of breathable gas, and vice-versa, enabling switching between two sources of breathable gas without interruption in supply.20.) The apparatus of claim 19 further comprising one or more apparatus features of claims 2 to 14.21 .) Use of a breathable gas supply apparatus comprising a valve means with a diving face mask or helmet, the gas supply apparatus being connected with a rebreather or reclaim unit for a first supply of breathable gas for closed-circuit use, and connected with a second supply of breathable gas for open-circuit use, wherein the use comprises: a) sealing or opening supply from the rebreather or reclaim unit; and b) opening or sealing supply from the second supply of breathable gas; wherein, sealing supply from the rebreather or reclaim unit corresponds to opening supply from the second supply of breathable gas, and vice-versa, enabling switching between two sources of breathable gas without interruption in supply.

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