Anaesthetic gas capture system

Abstract

An anaesthetic gas capture device housing two reusable canisters that safely capture volatile agents from the exhaust of an anaesthetic machine while maintaining a safe connection to a hospital AGSS and enabling the anaesthetic machine to continue to work in an active AGSS mode, without alteration, the device comprises or can be connected to suction means for drawing gas exhausted from a machine to the device, the suction means operates upstream of the capture canisters, the device is configured so that the suction means pushes gas through the canisters under positive pressure in series and agent extraction occurs under positive pressure, the device is pneumatically decoupled from the anaesthetic machine so that the device cannot apply vacuum pressure to the anaesthetic machine.

Description

[0001] ANAESTHETIC GAS CAPTURE SYSTEM

[0002] The present invention relates to generally to the capture of anaesthetic agents (e.g. halocarbons) and more particularly, although not exclusively, to apparatus (systems and / or parts thereof) for use in the capture of anaesthetic agents in medical environments.

[0003] This application claims priority from UK patent application number 2410777.3, the contents of which are incorporated by reference.

[0004] Examples of agents for which systems can be configured, adapted or provided include e.g. halogenated ethers (such as isoflurane, desflurane, and sevoflurane), halogenated hydrocarbons (such as halothane), nitrous oxide or xenon.

[0005] A halocarbon is an organic chemical molecule composed of at least one carbon atom bound covalently with one or more halogen elements. Halocarbons have many uses and are used in several industries as solvents, pesticides, refrigerants, fire-resistant oils, ingredients of elastomers, adhesives and sealants, electrically insulating coatings, plastics and anaesthetics. An alternative term for halocarbons is “halogenated fluorocarbons” when halogen elements other than fluorine are included in the molecule.

[0006] Volatile anaesthetic agents are typically halogenated fluorocarbons, examples of which include desflurane, isoflurane, sevoflurane and halothane. Volatile anaesthetic agents are liquid at room temperature but evaporate easily to produce a vapour for inhalation by a patient to induce anaesthesia. Anaesthetic agents are used extensively in modern healthcare and represent a significant cost. They are also potent greenhouse gases due to their ability to absorb infrared light and their upper atmospheric persistence. Isoflurane and Halothane also contain Chlorine and Bromine groups that contribute to ozone depletion.

[0007] Examples of halocarbons which are used as anaesthetic agents typically include desflurane, isoflurane, sevoflurane, halothane and enflurane. These anaesthetics may be referred to as volatile anaesthetic agents because they are liquid at room temperature but evaporate easily to produce a vapour for inhalation by a patient to induce anaesthesia. These agents are administered to patients using the breathing circuit of an ananaesthetic machine, also known as a Boyle’s machine. The primary function of the anaesthetic machine is to mix oxygen with volatile anaesthetic agent, at a clinician-specified concentration, for delivery to the patient via the breathing circuit.

[0008] The present invention seeks to provide improvements in or relating to the capture of anaesthetic agents from medical environments.

[0009] An aspect of the present invention provides an anaesthetic gas capture device for extracting anaesthetic agent from a gas flow, the device has an inlet and an outlet, the inlet receives flow from the exhaust of an anaesthetic machine, the device has a bypass mode and a capture mode, in the bypass mode a shut-off valve is closed and a fan is not running, the outlet is connectable to an Anaesthetic Gas Scavenging System (AGSS), flow is drawn through the device but no flow can enter through an air break because the shutoff valve blocks the route, and cannot reverse flow through the fan due to a non-return valve upstream of the fan, in the capture mode the shut off valve is open and the fan is running, the flow goes through an active canister first and then into a guard canister, on exiting the guard canister the flow is then drawn toward the AGSS (if fitted) through the open shut-off valve, the additional air that the AGSS is drawing is supplied via the air brake, there is no flow through the bypass, a flowmeter is now positioned downstream of the shut off valve to monitor fan and air brake flow magnitude, the non-return valve positioned at the air break inlet to prevent reverse flow (e.g. if the AGSS is low or not fitted).

[0010] In some embodiments the device is fitted with valves that allow canisters to be swapped while in operation.

[0011] In some embodiments, in a condition where both canisters have been removed the device automatically moves to the bypass condition so there is no interruption to gas flow through the device.

[0012] Load cells and canister sensors may be provided and work together to determine the presence and mass of individual canisters so that their capacity can be tracked and an indication of when they need to be replaced can be provided. An anaesthetic sensor may be provided at the inlet side of the device.

[0013] One or more fans may be provided upstream of the canisters and downstream of the sensor.

[0014] In some embodiments the sensor activates the fan / s when the level of anaesthetic detected in gas flow pulled from the anaesthetic machine is above a predetermined threshold.

[0015] The device may be automatically switchable between the capture mode and the bypass mode.

[0016] The device may be manually switchable between the capture mode and the bypass mode.

[0017] Some devices are configured for bi-directional flow, such that in-series filling of the two canisters can occur in either order.

[0018] A further aspect provides an anaesthetic gas capture device for extracting anaesthetic agent from a gas flow, the device has an inlet and an outlet, the inlet receives flow from the exhaust of an anaesthetic machine, the device housing two reusable canisters, Canister 1 and Canister 2, that safely capture volatile agents from the exhaust of an anaesthetic machine while maintaining a safe connection to a hospital AGSS and enabling the anaesthetic machine to continue to work in an active AGSS mode, without alteration, the device has a bypass mode and a capture mode, in the bypass mode a shut-off valve is closed and a fan is not running, the outlet is connectable to an Anaesthetic Gas Scavenging System (AGSS), flow is drawn through the device but no flow can enter through an air break because the shut-off valve blocks the route, and cannot reverse flow through the fan due to a non-return valve upstream of the fan, in which the capture mode has a forward flow mode and a reverse flow mode, in the forward flow mode the shut off valve is open and the fan is running, the flow through the fan is set to draw a required flow from the anaesthetic machine, the AGSS is connected to the outlet and is still flowing, two 3-way valves are both positioned to allow the flow path through Canister 1 first and then into Canister 2, on exiting Canister 2 the flow is then drawn toward the AGSS through the open shut off valve, the additional air that the AGSS is drawing is supplied via the air brake, air coming from the local environment, there is no flow through the bypass, the flowmeter is positioned downstream of the shut off valve to monitor fan and air brake flow magnitude, the non-return valve is positioned at the air break inlet to prevent reverse flow if the AGSS is low or not fitted, in the reverse flow mode the shut-off valve is open and the fan is running, the flow through the fan is set to draw a required flow from the anaesthetic machine, the AGSS is connected to the outlet and is still flowing two 3-way valves switch positions at the same time, both now allowing flow to the secondary port, the flow is now directed to Canister 2 first and then into Canister 1 , the flow can only flow into canister 2 as the flow toward shutoff valve is blocked by the 3-way valve, on exiting canister 1 flow is toward the shutoff valve and cannot flow toward the fan due to the 3-way valve, the additional air that the AGSS is drawing is supplied via the air brake, there is no flow through the bypass, the flowmeter is again positioned downstream of the shut off valve to monitor fan and air brake flow magnitude, the non-return valve positioned at the air break inlet to prevent reverse flow (e.g. if the AGSS is low or not fitted).

[0019] A further aspect provides an anaesthetic gas capture device housing two reusable canisters that safely capture volatile agents from the exhaust of an anaesthetic machine while maintaining a safe connection to a hospital AGSS and enabling the anaesthetic machine to continue to work in an active AGSS mode, without alteration, the device comprises or can be connected to suction means for drawing gas exhausted from a machine to the device, the suction means operates upstream of the capture canisters, the device is configured so that the suction means pushes gas through the canisters under positive pressure in series and agent extraction occurs under positive pressure, the device is pneumatically decoupled from the anaesthetic machine so that the device cannot apply vacuum pressure to the anaesthetic machine.

[0020] Devices may be formed as a mobile trolley.

[0021] Devices may be wall mountable.

[0022] The present invention also provides a mobile anaesthetic gas scavenging device comprising a device as described herein. The present invention also provides a medical environment provided with one or more devices as described herein.

[0023] Methods of extracting anaesthetic agent from a gas flow using an anaesthetic gas capture device are also provided.

[0024] Systems for extracting anaesthetic agent from a gas flow using an anaesthetic gas capture device are also provided.

[0025] The present invention relates, in some aspects and embodiments, to a waste volatile anaesthetic gas capture machine, housing reusable capture canisters (e.g. one, two, three or four) that safely capture volatile agents from the exhaust of an anaesthetic machine.

[0026] Devices may be configured to maintain a safe connection to the hospital anaesthetic gas scavenging system (AGSS) enabling the anaesthetic machine to continue to work in the active AGSS mode, without alteration.

[0027] Some aspects and embodiments of the present invention provide or relate to an anaesthetic gas capture device for extracting anaesthetic agent from a gas flow.

[0028] The device may comprise or may be connectable to suction means for drawing gas flow to the device.

[0029] The device may be configured to receive one or more capture canisters through which gas can flow.

[0030] The suction means may operate upstream of the capture canister / s whereupon the suction means pushes gas through the or one or more of the canisters under positive pressure and agent extraction occurs under positive pressure.

[0031] A reusable canister that captures available waste volatile anaesthetic agents through adsorption onto a sustainable carbon material.

[0032] Some embodiments may be configured for use with Desflurane, for example. The device may be configured or configurable to fill multiple canisters in series.

[0033] The (e.g. two) canisters in the device may fill up in series. One reason for this is that Desflurane, which is the most volatile anaesthetic agent (with a boiling point of 23C), is relatively easily displaced by the other anaesthetics. Using a "series" plumbing arrangement in a two canister system, for example, means that any Desflurane is merely displaced onto the 2ndcanister, rather than out of the device.

[0034] Embodiments of the present invention may be provided in the form of a Class 1 medical device that is easily installed and integrates simply, seamlessly and universally between the anaesthetic machine and the hospital anaesthetic gas scavenging system (AGSS).

[0035] The dock / device may house two reusable cans / canisters that safely capture volatile agents from the exhaust of an anaesthetic machine, while maintaining a safe connection to the hospital AGSS and enabling the anaesthetic machine to continue to work in the active AGSS mode, without alteration.

[0036] Some embodiments are configured to hold only two capture canisters. Other embodiments are configured to hold and use two or more capture canisters.

[0037] Example Safety Features

[0038] • Conforms to all required safety standards

[0039] • Failsafe bypass system to hospital AGSS

[0040] • Visual and audible indicators and safety alarms

[0041] • Enables high flows, nitrous oxide and oxygen flushing practice

[0042] • Automatic shut-off valves (enabling intraoperative SID-Can exchange)

[0043] • British Standard AGSS safety hoses

[0044] • Tamper-proof power cable connection

[0045] Example Sustainability Features

[0046] • Houses two reusable canisters

[0047] • No consumables required

[0048] • Low power consumption SID-lnsights and data capture

[0049] Example Ease of Use Features

[0050] • Integration without adaptation or calibration to the anaesthetic machine or hospital AGSS system

[0051] • Compatible with all major anaesthetic machine manufacturers

[0052] • No change to clinical practice and safety procedures operating in the active AGSS mode

[0053] • Intraoperative SID-Can exchange (‘hot-swap’)

[0054] • Touchscreen display with SID-Can percentage fill level and AGSS flow indicator

[0055] • Low maintenance with self-diagnostics and auto-calibration

[0056] • Wall mountable or free-standing options with small footprint

[0057] Example Features / Benefits

[0058] • Compatible with all major global anaesthetic machine brands

[0059] • Integrates into existing anaesthetic equipment without alteration

[0060] • Automatic failsafe bypass

[0061] • Requires no change in clinical practice

[0062] • Intraoperative SID-Can exchange (‘hot-swap’)

[0063] • Touchscreen display with SID-Can percentage fill level and AGSS flow indicator

[0064] • Visual and audible safety alarms

[0065] • Wall mountable or free-standing options

[0066] • Low maintenance with self-diagnostics and auto-calibration

[0067] • Small and compact design

[0068] • Reusable, lightweight and recyclable at end of life

[0069] • Safe to handle, store and transport

[0070] • Captured agent recorded

[0071] • Large capacity for fewer canister exchanges

[0072] The device may be configured to draw gas from an anaesthetic machine.

[0073] The device may be configured to draw from a patient.

[0074] The device may be configured to draw from a patient mask. The device may be pneumatically decoupled from the gas flow source so that the device cannot apply vacuum pressure thereto. An air break may, for example, be provided by the device and / or the source.

[0075] The device may comprise a sensor for sensing the presence of anaesthetic agent in gas flow.

[0076] The sensor may be provided on an inlet side of the device,

[0077] The suction means may be provided upstream of the capture canister / s and downstream of the sensor.

[0078] In some embodiments the sensor can activate the suction means when anaesthetic agent is detected.

[0079] The sensor may activate and / or deactivate the suction means based on detection of a threshold agent concentration or amount.

[0080] Devices of some embodiments have a capture mode and a bypass mode.

[0081] The device may be automatically switchable between the capture mode and the bypass mode. Alternatively or additionally the device may be manually switchable between the capture mode and the bypass mode.

[0082] The device may be connectable to a gas scavenging system.

[0083] The device may, for example, be connectable to an Anaesthetic Gas Scavenging System (AGSS).

[0084] In some embodiments the device may be configurable to be an AGSS replacement. The device may, for example, be configured to be pneumatically decoupled from a scavenging system when connected. An air break may, for example, be provided by the device and / or a scavenging system.

[0085] The device may be configured such that canisters can be removed / replaced during operation of the device.

[0086] Devices may comprise means for determining the remaining capacity of a canister.

[0087] Devices may comprise means for detecting the presence of a canister.

[0088] The suction means may, for example, be one or more of a vacuum source, a venturi pump or a fan.

[0089] In some embodiments, for example, the suction means comprises one or a plurality of fans.

[0090] Some devices comprise or can be associated with one or more air breaks.

[0091] Some embodiments comprise an air break formed within or between flow conduits.

[0092] Some embodiments comprising a bypass to receive flow when the suction means is inactive and / or to act as a high-pressure bypass.

[0093] Device may be formed as a mobile trolley.

[0094] Devices may be wall mountable.

[0095] The present invention also provides for a medical environment provided with one or more devices or systems as described herein.

[0096] In some embodiment canisters (e.g. two) fill up in series. The system may use a vacuum source. This could be an external or internal vacuum source, venturi pump, or fans. The vacuum pressure may be between 10-20kPa vacuum pressure with a flow rate between 50-80lpm, for example. These values could increase or decrease if there are changes to legislation.

[0097] An air break system may be provided that effectively pneumatically de-couples each of the systems so no over-pressure or vacuum condition can affect the patient.

[0098] The device may be fitted with valves that allow canisters to be swapped while in operation. In a condition where all canisters have been removed, the system moves to a bypass condition so there is no interruption to gas flow through the systems.

[0099] Load cells and canister sensors may be provided and work together to determine the presence and mass of individual canisters so that their capacity can be tracked and an indication of when they need to be replaced can be provided.

[0100] An anaesthetic sensor (e.g. a VOC sensor) may be provided at the inlet side of the device.

[0101] A vacuum source, such as a fan, may be provided upstream of the canisters (and downstream of the sensor).

[0102] The sensor may activate the fan when the level of VOC (anaesthetic) detected in gas flow pulled from the anaesthetic machine is high.

[0103] Because the fan is at the inlet side of the canister in some embodiments it pulls flow from the anaesthetic machine and pushes gas through the canister.

[0104] This means the system is not pulling a vacuum across the canister. This results in more efficient binding of anaesthetic agent onto the canister filter, because binding is happening in a positive and not a negative pressure environment. This also reduces duty of the vacuum source because it is not having to fight airway resistance provided by the filters in the canisters. Switching between capture and bypass modes, where provided, may be achieved manually and / or automatically.

[0105] Different aspects and embodiments of the invention may be used separately or together.

[0106] The present invention is also described, by way of example, with reference to the accompanying drawings.

[0107] All orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting on the invention or its connection to a closure.

[0108] Example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

[0109] Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed and as well as individual embodiments the invention is intended to cover combinations of those embodiments as well. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

[0110] The terminology used herein to describe embodiments is not intended to limit the scope. The articles “a,” “an,” and “the” are singular in that they have a single referent; however, the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and / or “including,” when used herein, specify the presence of stated features, items, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and / or groups thereof.

[0111] Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein.

[0112] The figures illustrate capture systems based on a medical device that is easily installed and can be integrated simply, seamlessly and universally between an anaesthetic machine and a hospital anaesthetic gas scavenging system (AGSS), for example.

[0113] Figures 1 to 8 shows a capture device 10 formed in accordance with an aspect of the present invention and comprising a main body 15.

[0114] The device 10 houses two reusable canisters 20, 25 that safely capture volatile agents from the exhaust of an anaesthetic machine, while maintaining a safe connection to the hospital AGSS and enabling the anaesthetic machine to continue to work in an active AGSS mode, without alteration.

[0115] The device comprises or can be connected to suction means for drawing gas exhausted from a machine to the rig.

[0116] The device is pneumatically decoupled from the anaesthetic machine so that the device cannot apply vacuum pressure to the machine.

[0117] Canister sensors are provided to detect the presence / absence of a canister in each canister bay.

[0118] A graphical user interface (GUI) 30 is provided on the body 15.

[0119] Schematic flow diagrams of an example capture device formed in accordance with embodiments of the present invention are shown. In the schematics the rig has been shown with a vacuum source. This could, for example, be an external or internal vacuum source, venturi pump, or fan / s. The vacuum pressure may, for example, be between 10- 20kPa vacuum pressure with a flow rate between 50-80lpm, for example.

[0120] Variant 1 - SID-Dock CV1

[0121] In this variant the flow through the canisters is in parallel.

[0122] Bypass mode - Figure 9A

[0123] • Shut off valve is closed and the fan is not running

[0124] • The AGSS is connected to the outlet and is nominally flowing at a rate of 60 to 100L / min

[0125] • Flow is drawn through the SID-Dock as shown by the red line, this is a short low impedance route

[0126] • No flow can enter through the SID-Dock air break because the valve blocks the route and cannot reverse flow through the fan due to the non-return valve.

[0127] Volatile capture flow - Figure 9B

[0128] • Shut off valve is open and the fan is running

[0129] • The flow through the fan is nominally 50L / min (this is set to draw the reguired flow from the Anaesthetic machine), the AGSS is connected to the outlet and is still flowing a nominal 60-100L / min

[0130] • The flow is egually split between the Canisters and flows in the same direction

[0131] • On exiting the Canisters the flow is then drawn toward the AGSS through the open shut off valve.

[0132] • The additional air that the AGSS is drawing being supplied via the air brake, air coming from the local environment (theatre air).

[0133] • No flow through the bypass

[0134] • Flowmeter positioned to monitor air brake flow magnitude and direction. Alarm conditions for low or reverse flow.

[0135] • Volatile capture flow shown by the red line.

[0136] Variant 2 - SID-Dock CV2

[0137] In this variant the flow through the canisters is in series. Bypass mode - Figure 10A

[0138] • Shut off valve is closed and the fan is not running

[0139] • The AGSS is connected to the outlet and is nominally flowing at a rate of 60 to 100L / min

[0140] • Flow is drawn through the SID-Dock as shown by the red line, this is a short low impedance route

[0141] • No flow can enter through the SID-Dock air break because the valve blocks the route, and cannot reverse flow through the fan due to the non-return valve upstream of the fan.

[0142] Volatile capture flow - Figure 10B

[0143] • Shut off valve is open and the fan is running

[0144] • The flow through the fan is nominally 50L / min (again set to draw the reguired flow from the anaesthetic machine), the AGSS is connected to the outlet and is still flowing a nominal 60-100L / min

[0145] • The flow now goes through the active canister first and then into the guard canister.

[0146] • On exiting the guard canister the flow is then drawn toward the AGSS through the open shut off valve.

[0147] • The additional air that the AGSS is drawing being supplied via the air brake, air coming from the local environment (theatre air via the internal SID-Dock air volume)

[0148] • No flow through the bypass

[0149] • Flowmeter now positioned downstream of the shut off valve to monitor fan and air brake flow magnitude. Alarm conditions for low flow.

[0150] • Non return valve positioned at the air break inlet to prevent reverse flow if the AGSS is low or not fitted.

[0151] • Volatile capture flow shown by the red line.

[0152] Variant 3 - SID-Dock CV2 with bi-directional Canister flow

[0153] Flow through the canisters is in series; flow can be directed through canister 1 then 2 or reverse flow through canister 2 and then 1 .

[0154] Bypass mode - Figure 11 A • Shut off valve is closed and the fan is not running

[0155] • The AGSS is connected to the outlet and is nominally flowing at a rate of 60 to 100L / min

[0156] • Flow is drawn through the SID-Dock as shown by the red line, this is a short low impedance route

[0157] • No flow can enter through the SID-Dock air break because the valve blocks the route and cannot reverse flow through the fan due to the non-return valve upstream of the fan.

[0158] Volatile capture forward flow - Figure 11 B

[0159] • Shut off valve is open and the fan is running

[0160] • The flow through the fan is nominally 50L / min (again set to draw the required flow from the anaesthetic machine), the AGSS is connected to the outlet and is still flowing a nominal 60-100L / min.

[0161] • The 2 off 3-way valves are both positioned to allow the flow path as indicated by the red lines.

[0162] • The flow now goes through Canister 1 first and then into Canister 2.

[0163] • On exiting Canister 2 the flow is then drawn toward the AGSS through the open shut off valve.

[0164] • The additional air that the AGSS is drawing is supplied via the air brake, air coming from the local environment (theatre air via the internal SID-Dock air volume)

[0165] • No flow through the bypass

[0166] • Flowmeter again positioned downstream of the shut off valve to monitor fan and air brake flow magnitude. Alarm conditions for low flow.

[0167] • Non return valve positioned at the air break inlet to prevent reverse flow if the AGSS is low or not fitted.

[0168] • Forward volatile capture flow shown by the red line.

[0169] Volatile Capture reverse flow - Figure 11 C

[0170] • Shut off valve is open and the fan is running

[0171] • The flow through the fan is nominally 50L / min (again set to draw the required flow from the anaesthetic machine), the AGSS is connected to the outlet and is still flowing a nominal 60-100L / min. • The 2 off 3-way valves are now switch position at the same time, both now allow flow to the secondary port, flow path as indicated by the red lines.

[0172] • The flow now directed to Canister 2 first and then into Canister 1 .

[0173] • The flow can only flow into canister 2 as the flow toward shutoff valve is blocked by the 3-way valve. On exiting canister 1 flow is toward the shutoff valve and cannot flow toward the fan due to the 3-way valve.

[0174] • The additional air that the AGSS is drawing is supplied via the air brake, air coming from the local environment (theatre air via the internal SID-Dock air volume)

[0175] • No flow through the bypass

[0176] • Flowmeter again positioned downstream of the shut off valve to monitor fan and air brake flow magnitude. Alarm conditions for low flow.

[0177] • Non return valve positioned at the air break inlet to prevent reverse flow if the AGSS is low or not fitted.

[0178] • Reverse volatile capture flow shown by the red line.

[0179] Dimensions, where shown, are merely by way of example and not limiting in any way.

[0180] Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention.

Claims

CLAIMS1 . An anaesthetic gas capture device for extracting anaesthetic agent from a gas flow, the device has an inlet and an outlet, the inlet receives flow from the exhaust of an anaesthetic machine, the device has a bypass mode and a capture mode, in the bypass mode a shut-off valve is closed and a fan is not running, the outlet is connectable to an Anaesthetic Gas Scavenging System (AGSS), flow is drawn through the device but no flow can enter through an air break because the shut-off valve blocks the route, and cannot reverse flow through the fan due to a non-return valve upstream of the fan, in the capture mode the shut off valve is open and the fan is running, the flow goes through an active canister first and then into a guard canister, on exiting the guard canister the flow is then drawn toward the AGSS through the open shut off valve, the additional air that the AGSS is drawing is supplied via the air brake, there is no flow through the bypass, a flowmeter is positioned downstream of the shut off valve to monitor fan and air brake flow magnitude, the non-return valve positioned at the air break inlet to prevent reverse flow if the AGSS is low or not fitted.

2. A device as claimed in claim 1 , in which the device is fitted with valves that allow canisters to be swapped while in operation.

3. A device as claimed in claim 1 or claim 2, in which in a condition where both canisters have been removed, the device automatically moves to the bypass condition so there is no interruption to gas flow through the device.

4. A device as claimed in any preceding claim, in which load cells and canister sensors are provided and work together to determine the presence and mass of individual canisters so that their capacity can be tracked and an indication of when they need to be replaced can be provided.

5. A device as claimed in any preceding claim, in which an anaesthetic sensor provided at the inlet side of the device.

6. A device as claimed in claim 5, in which the fan is provided upstream of the canisters and downstream of the sensor.

7. A device as claimed in claim 5 or claim 6, in which the sensor activates the fan when the level of anaesthetic detected in gas flow pulled from the anaesthetic machine is above a predetermined threshold.

8. A device as claimed in any preceding claim, in which the device is automatically switchable between the capture mode and the bypass mode.

9. A device as claimed in any preceding claim, in which the device is manually switchable between the capture mode and the bypass mode.

10. A device as claimed in any preceding claim and configured for bi-directional flow, such that in-series filling of the two canisters can occur in either order.

11. An anaesthetic gas capture device for extracting anaesthetic agent from a gas flow, the device has an inlet and an outlet, the inlet receives flow from the exhaust of an anaesthetic machine, the device housing two reusable canisters, Canister 1 and Canister 2, that safely capture volatile agents from the exhaust of an anaesthetic machine while maintaining a safe connection to a hospital AGSS and enabling the anaesthetic machine to continue to work in an active AGSS mode, without alteration, the device has a bypass mode and a capture mode, in the bypass mode a shut-off valve is closed and a fan is not running, the outlet is connectable to an Anaesthetic Gas Scavenging System (AGSS), flow is drawn through the device but no flow can enter through an air break because the shutoff valve blocks the route, and cannot reverse flow through the fan due to a non-return valve upstream of the fan, in which the capture mode has a forward flow mode and a reverse flow mode, in the forward flow mode the shut off valve is open and the fan is running, the flow through the fan is set to draw a required flow from the anaesthetic machine, the AGSS is connected to the outlet and is still flowing, two 3-way valves are both positioned to allow the flow path through Canister 1 first and then into Canister 2, on exiting Canister 2 the flow is then drawn toward the AGSS through the open shut off valve, the additional air that the AGSS is drawing is supplied via the air brake, air coming from the local environment, there is no flow through the bypass, the flowmeter is positioned downstream of the shut off valve to monitor fan and air brake flow magnitude, the nonreturn valve is positioned at the air break inlet to prevent reverse flow if the AGSS is low ornot fitted, in the reverse flow mode the shut-off valve is open and the fan is running, the flow through the fan is set to draw a required flow from the anaesthetic machine, the AGSS is connected to the outlet and is still flowing two 3-way valves switch positions at the same time, both now allowing flow to the secondary port, the flow is now directed to Canister 2 first and then into Canister 1 , the flow can only flow into canister 2 as the flow toward shutoff valve is blocked by the 3-way valve, on exiting canister 1 flow is toward the shutoff valve and cannot flow toward the fan due to the 3-way valve, the additional air that the AGSS is drawing is supplied via the air brake, there is no flow through the bypass, the flowmeter is positioned downstream of the shut off valve to monitor fan and air brake flow magnitude, the non-return valve positioned at the air break inlet to prevent reverse flow if the AGSS is low or not fitted.

12. An anaesthetic gas capture device housing two reusable canisters that safely capture volatile agents from the exhaust of an anaesthetic machine while maintaining a safe connection to a hospital AGSS and enabling the anaesthetic machine to continue to work in an active AGSS mode, without alteration, the device comprises or can be connected to suction means for drawing gas exhausted from a machine to the device, the suction means operates upstream of the capture canisters, the device is configured so that the suction means pushes gas through the canisters under positive pressure in series and agent extraction occurs under positive pressure, the device is pneumatically decoupled from the anaesthetic machine so that the device cannot apply vacuum pressure to the anaesthetic machine.

13. A device as claimed in any preceding claim and formed as a mobile trolley.

14. A device as claimed in any preceding paragraph and being wall mountable.

15. A mobile anaesthetic gas scavenging device comprising a device as claimed in any preceding claim.

16. A medical environment provided with one or more devices as claimed in any of preceding claim.

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