Methods and systems for gas detection

• US 20080030352A1
• Filed: 02/20/2007
• Published: 02/07/2008
• Est. Priority Date: 02/27/2006
• Status: Abandoned Application

• Current Assignee: Thorn Security Limited (Johnson Controls International plc)
• Original Assignee: Thorn Security Limited (Johnson Controls International plc)
• Inventors: Shaw, John
• Application Number:
  US11/708,172
• Publication Number:
  US 20080030352A1
• Time in Patent Office: Days
• US Class Current: 340/579
• CPC Class Codes: G01N 27/127 comprising nanoparticles
• CPC Class Codes: G08B 17/117 by using a detection device for specific gases, e.g. combustion products, produced by the fire G08B17/103, G08B17/11 take precedence
• CPC Class Codes: G08B 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence

Abstract

Methods and systems for detecting potential fire related conditions are provided. The system includes a sensor that includes a carbon-based nano-structure, the sensor exhibiting an electronic property that varies in response to a presence of a predetermined gas indicative of a potential fire related condition and an evaluation unit, communicating with the sensor, for analyzing the electronic property to determine whether the potential fire related condition exists.

Claims

1. A system for detecting a fire related condition, comprising:

a sensor that includes a carbon-based nano-structure, said sensor exhibiting an electronic property that varies in response to a presence of a predetermined gas indicative of a fire related condition; and

an evaluation unit, communicating with the sensor, for analyzing the electronic property to determine whether the fire related condition exists.

2. The system in accordance with claim 1, wherein the carbon-based nano-structure constitutes a carbon nanotube structure having carbon atoms linked in a cylindrical framework.

3. The system in accordance with claim 1, wherein the carbon-based nano-structure includes a structure comprising at least one of carbon nanotubes, fullerenes, carbon nanocones, carbon nano-onions, graphene sheet, and nanosized carbon particles of graphitic or amorphous type, and combinations or assemblies thereof.

4. The system in accordance with claim 1, wherein the carbon-based nano-structure including an approximately circular cross-section having a diameter of less than about 100 nanometers.

5. The system in accordance with claim 1, wherein the electronic properties of the carbon-based nano-structure that vary include at least one of current versus applied voltage, resistance, capacitance, impedance, field emission current, diode characteristics, and trans-conductance.

6. The system in accordance with claim 1, wherein the carbon-based nano-structure is responsive to gases that are at least one of generated or consumed by combustion, generated or consumed by fuel pyrolysis, and associated with false fire alarm conditions.

7. The system in accordance with claim 1, wherein the evaluation unit determines when the fire related condition constitutes at least one of combustion, pyrolysis, a leak of a gas of interest, a discharge of a liquid or solid material generating a predetermined gas of interest, and a chemical reaction of interest.

8. The system in accordance with claim 1, wherein said evaluation unit receives electrical sensor signals from the sensor and compares the sensor signals with a predetermined threshold to determine whether the fire related condition exists.

9. The system in accordance with claim 1, wherein said evaluation unit generates a control signal when the fire related condition exists, the control signal being used to at least one of generate an alert signal and initiate an automatic action that facilitates mitigating the fire related condition.

10. The system in accordance with claim 1, further comprising electrodes joined to said carbon-based nano-structure, the electrodes generating electrical sensor signals indicative of the electronic properties of the carbon-based nano-structure.

11. The system in accordance with claim 1 further comprising at least one of a scattered-light sensor, an ionization type smoke sensor, a light obscuration sensor, a flame electromagnetic emission sensor, an electrochemical carbon monoxide sensor, and a temperature sensor.

12. The system in accordance with claim 1 further comprising a housing at least partially surrounding said sensor, said housing comprising a gas permeable filter comprising materials with at least one of a size selective permeability, a physically selective permeability, a chemically selective permeability, an absorbent, a reactive, and a catalytic property wherein the materials are selectable based on a predetermined permeability profile.

13. The system in accordance with claim 1 further comprising a housing at least partially surrounding said sensor, said housing comprising a gas permeable filter that is electrically conductive, said filter configured to provide at least one of physical protection, electromagnetic screening, optical screening, and electrical contact to said carbon-based nano-structures.

14. The system in accordance with claim 1 wherein said carbon nanotube structures comprise at least one junction structure positioned at least one of between one or more carbon-based nano-structures and another electrically conducting or semiconductor material, between carbon-based nano-structures having different electronic properties wherein an electronic response to the presence of a predetermined gas is measured as a change in at least one of diode characteristics, thermoelectric characteristics, and thermoelectric power of the at least one junction structures.

15. The system in accordance with claim 1 wherein said carbon-based nano-structures comprise a field emission structure incorporating one or more carbon-based nano-structures wherein an electronic response to the presence of a predetermined gas is measured as a change in at least one of emission current and emission current versus potential characteristics of the field emission structure.

16. The system in accordance with claim 1 wherein said carbon-based nano-structures comprise a field effect transistor structure comprising three or more electrically conductive or semiconductive contacts disposed at least one of in contact with and adjacent to the carbon-based nano-structures wherein an electronic response to the presence of a predetermined gas is measured using said three or more electrical contacts as a change in at least one of current versus applied voltage, resistance, capacitance, impedance, diode characteristics, and field effect transistor characteristics, transconductance, and a change in applied potential for devices operated with fixed transconductance.

17. The system in accordance with claim 1 wherein said carbon-based nano-structures comprise an electrochemical cell structure incorporating one or more carbon-based nano-structures wherein an electronic response to the presence of a predetermined gas is measured as a change in at least one of electrode potential, cell current, and cell impedance.

18. The system in accordance with claim 1 wherein said carbon-based nano-structures comprise a device incorporating one or more carbon-based nano-structures wherein changes in the electronic properties of the carbon-based nano-structures are monitored using an interaction between the one or more carbon-based nano-structures with electromagnetic radiation.

19. The system in accordance with claim 18 wherein the electromagnetic radiation includes portions of the electromagnetic spectrum extending from ultraviolet to microwave radiation.

20. The system in accordance with claim 18 wherein an electronic response to the presence of a predetermined gas is measured as a change in at least one of radiation absorption, emission, and scattering.

21. The system in accordance with claim 20 wherein a change in at least one of radiation absorption, emission, and scattering includes a change in at least one of Raman, fluorescent, phosphorescent, and luminescent spectra.

22. The system in accordance with claim 1 wherein said carbon-based nano-structure comprises at least one of a single walled structure, a multi-walled structure, a semiconductor characteristic, a metallic characteristic, a band gap characteristic, structural chirality, substantially uniform nanotube lengths, non-uniform nanotube lengths, substantially uniform nanotube diameters, non-uniform nanotube diameters, and a presence of structural imperfections or defects.

23. The system in accordance with claim 1 wherein said carbon-based nano-structure comprises a net of carbon nanotubes having a density controlled such that the net of carbon nanotubes exhibits semiconductor properties.

24. The system in accordance with claim 1 wherein said carbon-based nano-structure comprises a net of single walled carbon nanotubes where net density is sufficiently low to maintain overall semiconductor properties for the nano-structure.

25. The system in accordance with claim 1 wherein said carbon-based nano-structure comprises a mat, net or body of carbon nanotubes, the carbon nanotubes being conditioned by reaction in an environment such that at least a portion of the carbon nanotubes are rendered non-conductive or have low conductivity thereby increasing the overall semiconductor properties of the carbon-based nano-structure

26. The system in accordance with claim 1 wherein said carbon-based nano-structure comprises a mat, net or body of carbon nanotubes that are conditioned by passing a current therethrough such that at least a portion of the metallic carbon nanotubes are thermally damaged or rendered non-conductive or to have low conductivity thereby increasing the overall semiconductor properties of the carbon-based nano-structure.

27. The system in accordance with claim 1 wherein said carbon-based nano-structures comprise at least one material addition such that the addition modifies at least one of the chemical sensitivity and the chemical selectivity of said carbon-based nano-structures.

28. The system in accordance with claim 27 wherein said material additions comprise additions that at least one of coat said carbon-based nano-structures and at least partially fill said carbon-based nano-structures.

29. The system in accordance with claim 27 wherein said material additions comprise additions that are in nanoparticulate form.

30. The system in accordance with claim 27 wherein said material additions comprise additions that are linked to said carbon-based nano-structures by at least one of covalent bonds and pi bonding interactions.

31. The system in accordance with claim 27 wherein said material additions comprise non carbon elements within said carbon-based nano-structures comprising at least one of nitrogen, boron, oxygen, silicon, sulfur, phosphorus, and germanium.

32. The system in accordance with claim 27 wherein said material additions comprise at least one of transition metals, lanthanide metals, catalytic metals, and metal compounds thereof.

33. The system in accordance with claim 27 wherein said material additions comprise at least one of Pt, Pd, Au, Ir, Rh, Ag, Co, Ni, and Cu.

34. The system in accordance with claim 27 wherein said material additions comprise at least one of polymeric material, macromolecular material, electrically conducting polymers, semiconductor polymers, polar polymers, polymers having acidic exchange sites, and polymers having ion exchange sites.

35. The system in accordance with claim 27 wherein said material additions comprise at least one of phthalocyanins, porphyrins, polycyclic aromatics, and organometallic compounds.

36. The system in accordance with claim 1 wherein said sensor includes a reference structure which is at least one of insensitive to and isolated from exposure to a predetermined gas indicative of a fire related condition such that output from said sensor in response to a presence of a predetermined gas indicative of a fire related condition is provided by the difference between variations of an electronic property of a carbon based nano-structure forming a sensing structure within said sensor and variations in the electronic properties of said reference structure.

37. The system in accordance with claim 36 where said reference structure includes a carbon based nano-structure

38. The system in accordance with claim 1 wherein heat or illumination is applied to said carbon-based nano-structures.

39. The system in accordance with claim 38 wherein said application of heat or illumination to said carbon-based nano-structures is varied in level, duration, or frequency.

40. The system in accordance with claim 39 wherein said variation in the application of heat or illumination to said carbon-based nano-structures is controlled in response to variations in the electronic properties of said carbon-based nano-structures.

41. The system in accordance with claim 40 wherein measurement of or of power requirements for said controlled variation in the application of heat or illumination to said carbon-based nano-structures in response to variations in the electronic properties is provided as a sensing input to a system for detecting a fire related condition.

42. A sensor for detecting a gas indicative of a fire related condition, the sensor comprising:

a carbon-based nano-structure configured to respond to the presence of a gas indicative of a fire related condition, the carbon-based nano-structure using a chemically responsive electronic property of the carbon nano-structure; and

an interface configured to transmit a signal indicative of a change in the electronic property in response to a presence of a predetermined gas generated by a fire related condition.

43. The sensor of claim 42, wherein the chemically responsive electronic property includes at least one of current versus applied voltage, resistance, capacitance, impedance, field emission current, diode characteristics, and trans-conductance.

44. The sensor of claim 42, wherein the carbon-based nano-structure constitutes a carbon nanotube structure having carbon atoms linked in a cylindrical framework.

45. The sensor of claim 42, wherein the carbon-based nano-structure including an approximately circular cross-section having a diameter of less than about one hundred nanometers.

46. The sensor of claim 42, wherein the carbon-based nano-structure including an approximately circular cross-section having a diameter of less than about fifty nanometers.

47. The sensor of claim 42, wherein the carbon-based nano-structure including an approximately circular cross-section having a diameter of less than about ten nanometers.

48. A method for detecting a fire related condition utilizing a sensor that includes a carbon-based nano-structure, the method comprising:

measuring an electronic property of the carbon-based nano-structure that varies in response to a presence of a predetermined gas indicative of a fire related condition; and

analyzing the electronic property to determine whether the fire related condition exists.

49. The method of claim 48 wherein analyzing the electronic property to determine whether the fire related condition exists comprises determining the presence of at least one of combustion, pyrolysis, a leak of a gas of interest, a discharge of a material generating a predetermined gas of interest, and a chemical reaction of interest.

50. The method of claim 48 wherein measuring an electronic property of the carbon-based nano-structure comprises measuring a change in an electronic property of a carbon-based nanotube structure wherein the carbon-based nanotube structure includes carbon atoms linked in a cylindrical framework having a diameter of less than about 100 nanometers.

51. The method of claim 48 wherein measuring an electronic property of the carbon-based nano-structure comprises measuring a change in at least one of a current versus applied voltage, resistance, capacitance, impedance, field emission current, diode characteristics, and trans-conductance.

52. The method of claim 48 wherein measuring an electronic property of the carbon-based nano-structure comprises measuring a change in an electronic property due to an interaction of the carbon-based nano-structure with at least one of electromagnetic radiation and ionizing radiation.