# US 2017/0108381 A1 · Flame detectors and associated methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0108381 A1 - Document ID: US20170108381A1 - Status: Published application - Kind: A1 - Application number: 15/297,325 - Filed: 2016-10-19 - Published: 2017-04-20 - Earliest claimed: 2015-10-19 - Assignees: FFE Limited - Applicants: FFE Limited - Inventors: Daniel Waldron - Web page: https://patentgrep.com/patent/US20170108381A1 ## CPC - G01J 5/0801: Means for wavelength selection or discrimination - G01J 5/0018: {Flames, plasma or welding} - G08B 17/12: Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions - G08B 29/185: {Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS ## Abstract A flame detector (1) including: a fire sensor (2a), capable of detecting a characteristic blackbody-type radiated heat signature emitted by a flaming material; and a guard sensor (2b), for detecting an at least further part of the spectrum emitted by the material and which serves to assist in rejecting false alarms, wherein, in use during detection of a flame, the guard sensor (2b) detects an amount of radiation G and the fire sensor (2a) detects an amount of radiation F, and positive detection of a flaming material depends upon the following criteria: F>0; G>0; and F>G. ## Claims ### Claim 1 A flame detector comprising: a fire sensor, capable of detecting a characteristic blackbody-type radiated heat signature emitted by a flaming material, the fire sensor being configured to detect an intensity of radiation F in a fire band range of wavelengths; and a guard sensor, for detecting an at least further part of a spectrum emitted by said material and which serves to assist in rejecting false alarms, the guard sensor being configured to detect an intensity of radiation G in a guard band range of wavelengths, and the guard sensor being configured to detect radiation of shorter wavelength than the fire sensor, wherein the guard band range of wavelengths is narrower than the fire band range of wavelengths and each band range of wavelengths is distinct from the other, and positive detection of the flaming material depends upon the following criteria: F>0; G>0; and F>G. ### Claim 2 (depends on 1) The flame detector as claimed in claim 1, wherein the fire sensor and/or guard sensor are arranged to operate in a wavelength region of less than 4 μm, less than 3.2 μm, less than 3 μm, or less than 2.55 μm, or, the fire sensor and/or guard sensor are arranged to operate in a wavelength region of from 0.6 μm to 3.2 μm, from 1 μm to 3.2 μm, or from 1 μm to 2.2 μm. ### Claim 3 (depends on 1) The flame detector as claimed in claim 1, wherein the guard band range of wavelengths and fire band range of wavelengths are separated by a sensory gap of 0.1 μm to 1 μm, of 0.2 μm to 0.8 μm, of 0.5 μm to 0.7 μm, or of 0.6 μm. ### Claim 4 (depends on 1) The flame detector as claimed in claim 1, wherein the guard band range of wavelengths detects over a range of 0.2 μm and the fire band detects over a range of 0.4 μm. ### Claim 5 (depends on 1) The flame detector as claimed in claim 1, wherein the fire sensor is configured to detect radiation having a wavelength range of: from 1.6 μm to 2.4 μm; from 1.7 μm to 2.3 μm; or from 1.8 μm to 2.2 μm. ### Claim 6 (depends on 1) The flame detector as claimed in claim 1, wherein the guard sensor is configured to detect radiation having a wavelength range of: from 0.6 μm to 1.4 μm; from 0.7 μm to 1.3 μm; from 0.8 μm to 1.2 μm; or from 1 μm to 1.2 μm. ### Claim 7 (depends on 1) The flame detector as claimed in claim 1, wherein the fire sensor and the guard sensor comprise a common sensor comprising PbS or InGaAs. ### Claim 8 A method for flame detection comprising: detecting an intensity of radiation F in a fire band range of wavelengths from a characteristic blackbody-type radiated heat signature emitted by a flaming material; and detecting an intensity of radiation G in a guard band range of wavelengths from an at least further part of a spectrum emitted by said material which serves in assisting rejection of false alarms, wherein, the guard band range of wavelengths are shorter than the fire band range of wavelengths, and the guard band range of wavelengths is narrower than the fire band range of wavelengths and each band range of wavelengths is distinct from the other, and detecting a flame if the following criteria are met: F>0; G>0; and F>G. ### Claim 9 (depends on 8) The method as claimed in claim 8 comprising detecting in a wavelength region of the spectrum of less than 4 μm, less than 3.2 μm, less than 3 μm or less than 2.55 μm, or, detecting in a wavelength region of from 0.6 μm to 3.2 μm, from 1 μm to 3.2 μm, or from 1 μm to 2.2 μm. ### Claim 10 (depends on 8) The method as claimed in claim 8 comprising arranging the guard band range of wavelengths and fire band range of wavelengths to be separated by a sensory gap of 0.1 μm to 1 μm, of 0.2 μm to 0.8 μm, of 0.5 μm to 0.7 μm, or of 0.6 μm. ### Claim 11 (depends on 8) The method as claimed in claim 8 comprising detecting the guard band range of wavelengths within a range of 0.2 μm and detecting the fire band range of wavelengths within a range of 0.4 μm. ### Claim 12 (depends on 8) The method as claimed in claim 8 comprising detecting fire band radiation having a wavelength range of: from 1.6 μm to 2.4 μm; from 1.7 μm to 2.3 μm; or from 1.8 μm to 2.2 μm. ### Claim 13 (depends on 8) The method as claimed in claim 8 comprising detecting guard band radiation having a wavelength range of: from 0.6 μm to 1.4 μm; from 0.7 μm to 1.3 μm; from 0.8 μm to 1.2 μm; or from 1 μm to 1.2 μm. ### Claim 14 (depends on 1) The flame detector as claimed in claim 1, wherein the fire sensor and the guard sensor are arranged to operate in infrared regions of the spectrum, wherein the guard sensor comprises a first guard sensor and a second guard sensor, the first guard sensor being configured to detect radiation of shorter wavelength than the fire sensor, and the second guard sensor being configured to operate in the infrared regions of the spectrum; wherein, during detection of a flame, the first guard sensor is configured to detect an intensity of radiation G1 in a first guard band range of wavelengths that is narrower than the fire band range of wavelengths and each band range of wavelengths is distinct from the other, and the second guard sensor is configured to detect an intensity of radiation G2 in a second guard band range of wavelengths, and positive detection of a flaming material depends upon the following criteria: F>0; G1>0; G2>0; F>G1; and F>G2. ### Claim 15 A flame detector comprising: a first sensor for detecting a characteristic blackbody-type radiated heat signature emitted by a flaming material, being configured to detect radiation is having a wavelength range of 1.6 μm to 2.4 μm; and a second sensor for detecting an at least further part of a spectrum emitted by said material and which serves to assist in rejecting false alarms, the second sensor being configured to detect radiation having a wavelength range of: from 0.6 μm to 1.4 μm, wherein each sensor comprises lead sulphide (PbS) or indium gallium arsenide (InGaAs). ### Claim 16 (depends on 15) The flame detector as claimed in claim 15, additionally comprising a third sensor for detecting within either the infrared or ultraviolet part of the spectrum. ### Claim 17 (depends on 15) The flame detector as claimed in claim 15, wherein the first sensor is configured to detect radiation having a wavelength range of 1.7 μm to 2.3 μm. ### Claim 18 (depends on 15) The flame detector as claimed in claim 15, wherein the first sensor is configured to detect radiation having a wavelength range of 1.8 μm to 2.2 μm. ### Claim 19 (depends on 15) The flame detector as claimed in claim 15, wherein the second sensor is configured to detect radiation having a wavelength range of 0.7 μm to 1.3 μm. ### Claim 20 (depends on 15) The flame detector as claimed in claim 15, wherein the second sensor is configured to detect radiation having a wavelength range of 0.8 μm to 1.2 μm. ### Claim 21 (depends on 15) The flame detector as claimed in claim 15, wherein the second sensor is configured to detect radiation having a wavelength range of 1 μm to 1.2 μm.