Fire detection device

Abstract

A fire detection device comprises a power source 12, a signalling circuit 14, an antenna 16 and a heat-activated trigger 15. The trigger activates at temperatures equal to or greater than 60C, and upo

Description

The invention relates generally to a fire detection device. More particularly, but not exclusively, the invention relates to a fire detection device comprising a heat-activated trigger. Background Wildfires pose a significant threat to ecosystems, human life, and property, causing extensive damage worldwide. Rapid detection and response are crucial to minimizing the destructive impact of these fires. Traditional methods of fire detection, such as lookout towers, satellite imagery, and ground patrols, have been employed with varying degrees of success. However, these methods often suffer from limitations including high operational costs, delayed detection times, and restricted coverage areas. Lookout towers require constant human monitoring, which is both labour-intensive and prone to human error. Satellite imagery provides extensive coverage but may not offer the necessary real-time detection capability due to the intervals between satellite passes and potential cloud cover. Ground patrols, while effective in localized areas, are not feasible for continuous monitoring over large, remote forested regions. Recent advancements have introduced automated fire detection systems, leveraging technologies such as thermal imaging cameras, infrared sensors, and smoke detectors. These systems, while promising, are often dependent on fixed installations that require a stable power supply and established communication infrastructure, which may not be available in remote forested areas. Further, for remote detection devices which are left in at-risk areas for prolonged periods of time, the time period before which the devices must be replaced is limited by the lifetime of the power source. It is also necessary to find and remove out-of-use devices to avoid polluting the area. The present invention was derived with the foregoing in mind. Summary of Invention According to a first aspect of the invention, there is provided a fire detection device. The fire detection device may comprise a power source. The fire detection device may comprise a signalling circuit. The fire detection device may comprise an output. The output may be an antenna. The fire detection device may comprise a trigger. The trigger may be configured to activate at temperatures equal to, or greater than, 60°C. The trigger may be configured to activate at temperatures equal to, or greater than, 70°C. The trigger may be configured to activate at temperatures equal to, or greater than, 80°C. Upon activation of the trigger, the power source may be configured to supply power to the signalling circuit to generate an output signal to be transmitted by the antenna. The use of a heat-activated trigger ensures that output signals are transmitted by the device when a fire is nearby. Having an activation temperature equal to or greater than 60°C ensures that air temperatures will only be hot enough to activate the trigger when there is a fire. The trigger may be, or comprise, a phase-change material which undergoes a phase change at temperatures equal to, or greater than, 60°C. The trigger may be, or comprises, a phase-change material which undergoes a phase change at temperatures equal to, or greater than, 70°C. The trigger may be, or comprises, a phase-change material which undergoes a phase change at temperatures equal to, or greater than, 80°C. The phase change may be a solid to liquid phase change. The phase change material may be non-toxic when burned. The use of a phase change material as a heat activated trigger provides a simple method for activation without requiring complex mechanisms. The use of a phase-change material as a trigger can ensure that the device is environmentally friendly by removing metallic wiring and various components and materials which would be present in sensors. The trigger may be part of the power source such that the power source is heat-triggered. This may ensure the power source lasts longer and does not lose charge until the trigger is activated. The power source may comprise an anode and a cathode, wherein the anode and cathode a separated so as to form a gap therebetween. The power source may comprise an electrolyte solution. The power source may comprise a barrier configured to isolate the electrolyte solution from the gap. The barrier may be the trigger. The barrier may be configured, in use, to undergo a phase change to release the electrolyte solution into the gap between the anode and cathode. The power source may comprise a separator disposed in the gap between the anode and cathode. The separator may be configured to prevent contact between the anode and cathode. The separator may be configured, upon release of the electrolyte solution, to absorb the electrolyte solution. The barrier may be configured, in use, to melt at temperatures equal to, or greater than, at least 60°C so as to release the electrolyte solution. The barrier may be configured, in use, to melt at temperatures equal to, or greater than, at least 70°C so as to release the electrolyte solution. The barrier may be configured, in use, to melt at temperatures equal to, or greater than, at least 80°C so as to release the electrolyte solution. The barrier may be formed of, or comprise, wax or a wax composite. The separator may be formed of, or comprise, paper. The separator may be formed of, or comprise, a cellulose-based structure. The cathode may be formed of, or comprise, activated charcoal. The anode may be formed of, or comprise, aluminium. The electrolyte may be formed of, or comprise, a saltwater solution. The power source may consist exclusively of materials which are non-toxic when burned. The signalling circuit may be configured to generate an output signal. The output signal may be a periodic oscillating signal. The output signal may have a periodic "beat" to enable the signal to be identified. The signalling circuit may comprise one or more signal generators. The signalling circuit may comprise a first signal generator, configured to generate a first signal. The signalling circuit may comprise a second signal generator, configured to modify the first signal to provide the output signal. The signalling circuit may comprise a quartz crystal oscillator. The signalling circuit may comprise an organic ring oscillator. The output signal may be a radio-frequency output signal. The output signal may have a frequency range between 3-30MHz. The output signal may have an loT frequency, such as 434MHz or 915MHz. The antenna may be formed of, or comprise, activated charcoal. The antenna may be formed of, or comprise, a composite comprising charcoal, a binding agent, and a cross-linking agent. The binding agent may be Xantham gum or CMC (Tylo powder). The cross-linking agent may be Citric Acid. The fire detection device may comprise a casing formed of, or comprising, a material which is non-toxic when burned. According to a second aspect of the invention, there is provided a system for detection of fires. The system may comprise one or more of the fire detection devices. The fire detection devices may be the fire detection devices defined in the first aspect of the invention. The system may comprise one or more receivers. The receiver may be configured to detect one or more output signal(s) transmitted by the fire detection device(s). The receivers may be dedicated receivers for the system, or they may be pre-exisitng and / or multi-purpose receivers. The system may comprise at least three receivers. The use of at least three receivers may enable the use of triangulation to determine to location of a device transmitting an output signal. The system may comprise a server. The receivers may be configured to communicate with the server in response to detection of one or more output signal(s) transmitted by the fire detection device. The server may be a cloud server. The server may be configured to receive external data, such as weather data or satellite data. The server may be configured to send alerts and / or warnings messages / signals based on data received from the receivers. The server may be configured to send alerts and / or warnings messages / signals based on data received from the receivers together with external data. According to a third aspect of the invention, there is provided a method of detecting a fire. The method of the third aspect may be performed using the system of the second aspect of the invention. The method may comprise deploying one or more fire detection devices. The fire detection devices may be fore detection devices of the first aspect of the invention. The method may comprise transmitting, via the one or more fire detection devices, one or more output signals in response to activation of one or more of the fire detection devices. The method may comprise detecting, via one or more receivers, the one or more output signal(s). The method may comprise determining the location of the source of the one or more output signal(s) using triangulation. The method may comprise sending a warning signal in response to detection of the one or more output signal(s) by the one or more receivers. Optional features of any of the above aspects may be combined with the features of any other aspect, in any combination. For example, features described in connection with the device of the first aspect may have corresponding features definable with respect to the system of the second aspect, and vice versa, and these embodiments are specifically envisaged. Features which are described in the context or separate aspects and embodiments of the invention may be used together and / or be interchangeable wherever possible. Similarly, where features are, for brevity, described in the context of a single embodiment, those features may also be provided separately or in any suitable subcombination. Brief description of the drawings The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of a fire detection device; Figures 2(a) and (b) respectively show regular and sectional perspective views of a fire detection device; Figure 3 shows an exploded view of a power source; Figure 4 shows a schematic view of a signalling circuit; Figure 5 shows a plan view of the internal components of a fire detection device; Figures 6(a) and (b) show partially transparent top and side views of a fire detection device; Figure 7 shows a sectional view of a fire detection device; Figures 8(a) and (b) show the use of a system for detecting fires; Figures 9(a) and (b) show the use of a system for detecting fires; Figures 10(a) and (b) show the use of a system for detecting fires; Figure 11 shows a flowchart representing a method for detecting fires. Detailed description Figure 1 shows a schematic view of a fire detection device 10. The fire detection device 10 comprises a power source 12, a signalling circuit 14, and an output 16. The fire detection device 10 comprises a trigger 15. Although the trigger 15 is shown as a distinct component in device 10, in other examples the trigger 15 can be integral with one of the other components. The fire detection device 10 is configured, in use, to detect the presence of a nearby fire. The fire detection device 10 is configured to activate in response to exposure to high temperatures which result from fires. Activation of the device 10 is caused by activation of the trigger 15. Upon activation of the trigger 15, the power source 12 supplies power to the signalling circuit 14, which generates an output signal which is transmitted by the output 16. In some examples, the output 16 is an antenna. The trigger 15 is configured to activate at temperatures equal to, or greater than, at least 60°C. In other examples, the trigger 15 is configured to activate at temperatures equal to, or greater than, at least 70°C. In other examples, the trigger 15 is configured to activate at temperatures equal to, or greater than, at least 80°C. Figures 2(a) and 2(b) shows perspective views of an example fire detection device 100. Figure 2(b) shows a sectional view of the fire detection device 100. The fire detection device 100 comprises a power source 112, a signalling circuit 114, and an antenna 116. The fire detection device 100 comprises a casing 118 which encloses the power source 112, signalling circuit 114, and antenna 116. The power source 112 is heat-activated. The power source 112 comprises a trigger (not labelled in Figure 2). The power source 112 is shown in greater detail in Figure 3. The power source 112 comprises an anode 120 and a cathode 122. The anode 120 and cathode 122 are positioned such that there is a gap between them to prevent direct contact therebetween. A separator 124 is disposed in the gap between the anode 120 and cathode 122 and prevents contact between the anode 120 and cathode 122. In other examples, the separator 124 can be omitted, and an air gap can present between the anode 120 and cathode 122. The power source 112 comprises an electrolyte solution 128, and a barrier 115 configured to isolate the electrolyte solution from the anode 120, cathode 122, and separator 124. The barrier 115 is the trigger in this example. The barrier 115 is configured, in use, to release the electrolyte solution 128 into the gap between the anode 120 and cathode 122 to be absorbed into the separator 124 (in examples without a separator, the electrolyte 128 enters the gap without being absorbed). The electrolyte solution 128 bridges the anode 120 and cathode to activate the power source 112. The barrier 115 is configured to release the electrolyte solution 128 in response to exposure to high temperatures. The barrier 126 is configured to melt when exposed to high temperatures to release the electrolyte solution 128. In some examples, the barrier is formed of, or comprises, a wax or wax composite. In some examples, the barrier is configured to melt when exposed to temperatures exceeding 60°C. In some examples, the barrier is configured to melt when exposed to temperatures exceeding 70°C. In some examples, the barrier is configured to melt when exposed to temperatures exceeding 80°C. In other examples, the barrier 115 can be formed of, or comprise, alternative materials which undergo a phase-change so as to release the electrolyte solution. In some examples, the separator 124 is formed of, or comprises, paper. In some examples, the separator 124 is formed of, or comprises, any other cellulose-based material. In other examples, the separator 124 can be any material which can absorb the electrolyte solution 128, or can be omitted entirely. In some examples, the separator can be formed of, or comprise, organic polymers with micropores. In some examples, the separator can be formed of, or comprise, polymeric membranes made of polyolefin based materials with a semi-crystalline structure, such as polyethylene, polypropylene, or PVC. In some examples, the cathode 122 is formed of, or comprises, activated charcoal. In other examples, the cathode can be formed of, or comprise, other carbon-rich materials, organic cathodic compounds, or readily oxidizing metals such as zinc and magnesium. In some examples, the anode 120 is formed of, or comprises, aluminium. In some examples, the anode is formed of, or comprises, aluminium foil. In other examples, other conventional anode materials can be used. In some examples, the electrolyte solution is formed of, or comprises, a saltwater solution. In other examples, the electrolyte solution can be any well-known electrolyte. In other examples, alternative heat-trigger mechanisms can be used. For example, a phase change material can melt to enable contact between two conductive portions so as to complete an electrical circuit. Completion of the electrical circuit can activate the power source and / or connect the power source to the signalling circuit. The signalling circuit 114 of the fire detection device 100 of Figure 2 is shown in greater detail in Figure 4. The signalling circuit 114 comprises a first signal generator 114-1 configured to generate a first signal. The signalling circuit 114 comprises a second signal generator 114-2 configured to generate a second signal. The first and / or second signal can be periodic signals oscillating signals, such as sinusoidal signals, square-wave signals, or triangular-wave signals. In the example of Figure 4, the second signal is used to modify the first signal to provide the output signal. In the example of Figure 4, the second signal periodically opens / closes a switch 114-3 which grounds the first signal. As such, there is a periodic grounding of the first signal which creates a detectable ‘"beat”. The periodically grounded first signal is the output signal transmitted by the output 116. In some examples, the periodic "‘beat” from the second signal generator can be used to identify signals from the device 100 relative to background signals from other sources. In some examples, each device has a unique “beat”. In other examples, each device has the same “beat”. In some examples, the first and / or second signal generator 114-1 / 2 is formed of, or comprises, materials which are non-toxic when burned. In some examples, the first and / or second signal generator 114-1 / 2 is formed of, or comprises, organic materials. For example, the first and / or second signal generator can comprise one of a quartz crystal oscillator or an organic ring oscillator. In some examples, one or more of the signal generators are MEMS oscillators. In some examples, the output signal is a radio-frequency output signal. In some examples the output signal has a frequency range between 3-30MHz. In some examples, the first signal generated by the first signal generator 114-1 is a radio-frequency signal, and the second signal generated by the second signal generator 114-2 can have any frequency. In other examples, alternative frequency ranges can be used. In some examples, the output signal has an “internet of things (IoT)” frequency, such as 434MHz or 915MHz. In other examples alternative signalling circuits 114 can be used. The alternative signalling circuits can comprise one or more signal generators. In some examples, the output is an antenna. In some examples, the antenna is formed of, or comprises, an organic material. In some examples, the output is an antenna. In some examples, the antenna is formed of, or comprises, a material which is non-toxic when burned. In the example device 100 of Figure 2, the antenna is formed of, or comprises charcoal or a charcoal composite. In other examples, the antenna can be formed of, or comprise, conventional metals such as copper. In other examples, the antenna can be formed of, or comprise, a carbon fiber composite, an organic conducting polymer composite, or a metallic nanoparticle embedded composite. In some examples, the antenna is formed of, or comprises, a composite comprising processed charcoal powder along with a binding agent and a cross-linking agent. In some examples, the binding agent is Xanthan gum or CMC (Tylo powder). In some examples, the cross-linking agent is Citric Acid. In some examples, the antenna is a composite comprising: • 95% (by wt.) Charcoal Powder • 4% (by wt.) Xanthan Gum • 1% (by wt.) Citric Acid CMC (Tylo powder) and Xanthan Gum are both bio-friendly and “greenly-derived" binding agents. In some examples, the use of citric acid, as a cross-linking agent, enhances this binding agent giving it advanced strength and potentially greater conductivity. The casing 118 encloses the other components of the fire detection device 100. The casing is formed of, or comprises, organic materials which are non-toxic when burned. In some examples, the casing 118 comprises mycelium insulation for heat management and shock protection, together with a biobased composite formed of, or comprising, natural fibres and a natural resource-based resin for structural stability, environmental protection, and shock protection. In some examples, the casing is biobased and nontoxic when burned, with good fire safety, shock protection and structural integrity, and appropriate outdoor ratings (IP, UV, temperature and humidity cycling and shock absorption). Figure 5 shows a plan view of the power source 112, signalling circuit 114 and antenna 116 (i.e., the circuitry of the device 100). The signalling circuit 114 is positioned between the power source 112 and antenna 116. Figures 6(a) and 6(b) respectively show7 partially transparent top and side views of the device 100 to illustrate how the circuitry (power source 112, signalling circuit 114, and antenna 116) fits inside a hollow cavity of the casing 118. Although the circuitry is substantially planar in the example device 100, in other examples the circuitry can be arranged differently and the casing 118 can be reshaped accordingly. Figure 7 shows a sectional view of an example of an alternative fire detection device 200. The main difference between the fire detection device 200 and the fire detection device 100 is that a different trigger is used and the trigger 215 is not part of the power source. The fire detection device 200 comprises a conventional power source 212 which, in some examples, can be a battery. The fire detection device 200 comprises a signalling circuit comprising a first signal generator 214-1 and a second generator 214-2. The power source is 212 is configured to supply power to the signalling circuit when the trigger 215 is activated. The trigger 215 comprises two conductive wires 215-3, 4 which, in some examples, are formed of, or comprise, charcoal. The trigger 215 comprises a conductive spring 215-1 and a barrier 215-2 formed of, or comprising, a phase-change material such as wax. When the barrier 215-2 reaches a high temperature due to proximity of a fire, the barrier 215-2 melts and enables the spring 215-1 to expand to create an electrical contact between the conductive wires 215-3, 4. Creating an electrical contact between the conductive wires 215-3, 4 completes an electrical circuit which enables power to be supplied to the signalling circuit 214 from the power supply 212. The fire detection device 200 comprises an antenna 216 which, in some examples if formed of, or comprises charcoal. The fire detection device 200 comprises a casing 218. The casing 218 encloses the other components of the fire detection device 200. The casing is formed of, or comprises, organic materials which are non-toxic when burned. In some examples, the fire detection device comprises a locating receiver configured to detect locating signals transmitted by a locator. In some examples, the locating receiver is part of the antenna. In some examples, the locating receiver is configured to detect locating signals having a radio frequency. The locating receiver may be configured to harvest energy from a received locating signal and use the energy to output a return signal. For example, RFID technology can be used to passively provide a return signal. In some examples, the return signal can be output using the signalling circuit and antenna. In other examples, the return signal is output using a secondary signalling circuit and / or a secondary antenna. In some examples, the return signal has the same frequency as the output signal would have from the signalling circuit. In other examples, the return signal has a different frequency. In some examples, the return signal has the same frequency as the output signal would have but with a different ‘‘beat”. The return signals can be detected (for example, by the device generating the initial locating signal) to locate the fire detection device. A system 1000 for detecting fires and its operation is described below in relation to Figures 8(a) and (b), 9(a) and (b), and 10(a) and (b) Figure 8(a) shows a plurality of fire detection device 1100 distributed throughout an area at risk of fire damage. For example, areas at risk of fire damage include, but are not limited to, forests, grasslands, and shrublands. The fire detection devices 1100 each comprise: a power source, a signalling circuit, an antenna, and a heat-activated trigger. In some examples, the triggers of each device are configured to activate at temperatures equal to, or greater than, at least 80°C. Upon activation of a trigger, the power source of the relevant device 1100 supplies power to the signalling circuit, which generates an output signal which is transmitted by the antenna. In some examples, the fire detection devices 1100 can be the fire detection device 100 of Figures 2-6 or the fire detection device 200 of Figure 7. In other examples, alternative fire detection devices 1100 can be used. The devices 1110 can be distributed throughout the at-risk area via a plurality of different methods. In some examples, and particularly for large areas, helicopters can be used to drop the fire detection devices 110 across the area. In other examples, the devices 1100 can be dropped using different vehicles, or can be manually dropped by personal. Until the devices are activated, they remain dormant and do not transmit any signals. Figure 8(b) shows a fire 1300 which has begun to spread in the at-risk area. One of the plurality of devices 1100 is proximate the fire and is activated due to temperature increase created by the fire. More specifically, the fire provides sufficient heat to increase the temperature of the device 1100 so as to activate the trigger of the relevant device 1100. Upon activation, the device begins to continually transmit an output signal. As the fire spreads, more fire detection devices 1100 are activated as a result of the heat from the fire. As shown in Figure 9(a), the system 1000 comprises a plurality of receivers 1400. The receivers 1400 are configured to detect output signals transmitted from the plurality of fire detection devices 1100. In some examples, the system 1000 comprises at least three receivers 1400. The use of at least three receivers 1400 enables the location of an activated (i.e., transmitting) fire detection device 1100 to be located via triangulation. Data from the receivers 1400 can be transferred to a server 1700, such as a cloud server. At the server 1700, the data sent from the receivers 1400 is used to determine the presence and preferably the location of activated fire detection devices 1100. In some examples, the server 1700 also receives data from external sources. For example, the server 1700 can receive data from satellites 1600 and / or weather data 1500. The use of weather data 1500 and / or satellite 1600 data can be used to assess the likelihood of a fire in the area for which the fire detection device 1100 is activated in order to identify false positives. As shown in Figure 10(a), in response to detection of a signal from a fire detection device 1100, warning signals can be sent from the server 1700 to relevant people and / or locations. For example, the fire detection device 1100 can send waring signals to nearby communities which would be at risk due to the fire, or the firefighting services. As shown in Figure 10(b), when the fire reaches and engulfs the activated detection device 1100, the device 1100 burns. The fire detection devices 1100 are formed of, or comprise, non-toxic materials which decompose and do not emit toxic gases when burned. As such, the fire detection devices decompose after use without leaving waste behind which could be harmful to the environment. Figure 11 shows a flowchart 2000 representing a method for detecting fires. The method comprises deploying 2100 a plurality of fire detection devices. The fire detection devices can be any of the fire detection devices described herein. The fire detection devices can be distributed across an at-risk area. The method comprises transmitting 2200, via at least one of the plurality of fire detection devices, an output signal. As described above in relation to the description of the system and devices, the devices are activated in response to exposure to heat from a nearby fire and, one activated, they transmit and output signal. The method comprises receiving 2300, at one or more receivers, the output signal(s) transmitted by the activated fire detection devices. The method can comprise receiving the one or more output signal(s) via at least three receivers and locating the activated devices (and hence the location of the fire) via triangulation. In some examples, data from the receivers is transferred to a server. In some examples, the method can comprise receiving weather data and / or satellite data. At the server, the weather data and / or satellite data can be analysed to determine the likelihood of a false positive (i.e., activation of a fire detection device without the presence of a fire). Finally, the method comprises transmitting 2400 one or more warning signals in response to receiving the one or more output signal(s). Warning signals can be transmitted to fire fighters, rescue teams, nearby communities, and / or any other relevant service. From reading the present disclosure, other variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known in the art of fire detection, and which may be used instead of, or in addition to, features already described herein. Although the appended claims are directed to particular combinations of features, it should be understood that the scope of the disclosure of the present invention also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. Features which are described in the context of separate examples may also be provided in combination in a single example. Conversely, various features which are, for brevity, described in the context of a single example, may also be provided separately or in any suitable sub-combination. The applicant hereby gives notice that new claims may be formulated to such features and / or combinations of such features during the prosecution of the present application or of any further application derived therefrom. For the sake of completeness, it is also stated that the term "comprising" does not exclude other elements or steps, the term “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several means recited in the claims and any reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

1. A fire detection device, comprising:a power source;a signalling circuit;an antenna; anda trigger;wherein the trigger is configured to activate at temperatures equal to, or greater than, 60°C; andwherein, upon activation of the trigger, the power source supplies power to the signalling circuit, which generates an output signal which is transmitted by the antenna.

2. The fire detection device of claim 1, wherein the trigger is, or comprises, a phase-change material which undergoes a phase change at temperatures equal to, or greater than, 60°C.

3. The fire detection device of claim 1 or claim 2, wherein the trigger is part of the power source such that the power source is heat-triggered.

4. The fire detection device of claim 3, wherein the power source comprises: an anode;a cathode, wherein the anode and cathode a separated so as to form a gap therebetween;an electrolyte solution; anda barrier configured to isolate the electrolyte solution from the gap;wherein the barrier is the trigger and is configured, in use, to undergo a phase change to release the electrolyte solution into the gap.

5. The fire detection device of claim 4, further comprising a separator disposed in the gap between the anode and cathode, wherein the separator is configured to prevent contact between the anode and cathode; andwherein the separator is configured, upon release of the electrolyte solution, to absorb the electrolyte solution.

6. The fire detection device of claim 4 or claim 5, wherein the barrier is configured, in use, to melt at temperatures equal to, or greater than, at least 80°C so as to release the electrolyte solution.

7. The fire detection device of any of claims 4-6, wherein the barrier is formed of, or comprises, wax or a wax composite.

8. The fire detection device of any of claims 5-7, wherein the separator is formed of, or comprises, paper.

9. The fire detection device of any of claims 4-8, wherein the cathode is formed of, or comprises, activated charcoal.

10. The fire detection device of any of claims 4-9, wherein the anode is formed of, or comprises, aluminium.

11. The fire detection device of any of claims 4-10, wherein the electrolyte is formed of, or comprises, a saltwater solution.

12. The fire detection device of any preceding claim, wherein the signalling circuit comprises:a first signal generator, configured to generate a first signal; anda second signal generator, configured to modify the first signal to provide the output signal.

13. The fire detection device of any preceding claim, wherein the signalling circuit comprises one of a quartz crystal oscillator or an organic ring oscillator.

14. The fire detection device of any preceding claim, wherein the output signal is a radio-frequency output signal.

15. The fire detection device of claim 14, wherein the output signal has a frequency range between 3-30MHz.

16. The fire detection device of any preceding claim, wherein the antenna is formed of, or comprises, activated charcoal.

17. The fire detection device of any preceding claim, further comprising a casing formed of, or comprising, a material which is non-toxic when burned.

18. A system for detection of fires, the system comprising:one or more of the fire detection devices defined in any previous claim; andone or more receivers configured to detect one or more output signal(s) transmitted by the fire detection device(s).

19. The system of claim 18, comprising at least three receivers.

20. The system of claim 18 or claim 19, further comprising a server, wherein thereceivers are configured to communicate with the server in response to detection of one or more output signal(s) transmitted by the fire detection device.

21. The system of claim 20, wherein the server is a cloud server.

22. The system of claim 20 or claim 21, wherein the server is configured to receiveexternal data, such as weather data or satellite data.

23. A method of detecting a fire, comprising:deploying one or more fire detection devices as defined in any of claims 1-17;transmitting, via the one or more fire detection devices, one or more output signals in response to activation of one or more of the ire detection devices; anddetecting, via one or more receivers, the one or more output signal(s).

24. The method of claim 23, further comprising:determining the location of the source of the one or more output signal(s) using triangulation.

25. The method of claim 24, further comprising:sending a warning signal in response to detection of the one or more output signal(s) by the one or more receivers.

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