Detect toxic emissions
Most gases (methane, sulfur hexafluoride (SF6), carbon monoxide and hundreds of others) are not visible to the naked eye, like the gases in the air around us. But can toxic emissions be detected with a thermal camera?
The answer is yes, with models specifically for viewing gas leaks. Most thermal imaging cameras cannot detect gases directly, but optical gas detection (OGI) cameras are highly specialized thermal cameras with spectral filters to visualize specific gas emissions.
Many gases invisible to the naked eye can be visualized with optical gas detection.
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How does optical gas detection work?
Many gas compounds absorb some infrared energy, but only within certain wavelength ranges. Most hydrocarbons (benzene, butane, and methane, for example= absorb radiation near the 3.3 μm (micrometer) wavelength, while a compound such as SF6 absorbs energy near 10.6 μm. (Some hydrocarbons have several absorption peaks in the IR spectrum, such as methane, which also absorbs near 7.7 μm, but with a filtered OGI camera it should be easy to visualize these gas leaks).
An OGI camera uses a unique spectral filter mounted on the front of the detector that restricts the wavelengths of radiation that can pass through the detector to a very narrow band called the bandpass.
Within this very narrow range, aimed at a specific gas, OGI cameras can visualize where there is a column of gas, which usually looks like a cloud of smoke, blocking the energy from reaching the IR detector. This cloud is where the gas is absorbing the energy at that wavelength.
For more information on how an OGI camera works, see FLIR's article The Science Behind Optical Gas Detection.
Can all gases be seen with infrared thermal technology?
Since OGI cameras image the gas as an absence of infrared energy, if a gas does not absorb infrared radiation in the bandpass, it cannot be imaged directly with an optical gas detection camera. For example, noble gases such as hydrogen, oxygen and nitrogen cannot be imaged directly. And even if a camera can image a specific gas, hydrocarbon gases, for example, it will not image another gas that has radically different infrared absorption properties, such as SF6. That is why FLIR has a range of OGI cameras for the detection of different gases.
Can a gas be identified with thermography?
OGI cameras are excellent for detecting gas leaks. However, this process does not lead directly to gas identification: it is necessary to know in advance which spectral filter should be used for the specific absorption band of the gas in question. Nor can a camera specify which gas of a gas "family" is being detected. For example, a camera viewing hydrocarbon gases will not be able to tell you which hydrocarbon is being viewed.
Carbon dioxide is made visible with a gas detection camera.
Learn about the gas detection cameras offered by FLIR to learn more about how these cameras are used to detect gas leaks quickly and safely.
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