page_title: Exhaust gas
section_title: Cold engines
hierarchical_section_title: Exhaust gas / Cold engines
caption_attribution_description: Exhaust from the tailpipe of a car. In this case, it is probably mostly water vapour that is seen.
context_page_description: Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline, petrol, biodiesel blends, diesel fuel, fuel oil, or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack, or propelling nozzle. It often disperses downwind in a pattern called an exhaust plume.
  It is a major component of motor vehicle emissions, which can also include:
  Crankcase blow-by
  Evaporation of unused gasoline
  Motor vehicle emissions contribute to air pollution and are a major ingredient in the creation of smog in some large cities. A 2013 study by MIT indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions. According to another study from the same university, traffic fumes alone cause the death of 5,000 people every year just in the United Kingdom.
context_section_description: During the first two minutes after starting the engine of a car that has not been operated for several hours, the amount of emissions can be very high. This occurs for two main reasons:
  Rich air-fuel ratio requirement in cold engines: When a cold engine is started, the fuel does not vaporize completely, creating higher emissions of hydrocarbons and carbon monoxide, which diminishes only as the engine reaches operating temperature. The duration of this start-up phase has been reduced by advances in materials and technology, including computer-controlled fuel injection, shorter intake lengths, and pre-heating of fuel and/or inducted air.
  Inefficient catalytic converter under cold conditions: Catalytic converters are very inefficient until warmed up to their operating temperature. This time has been much reduced by moving the converter closer to the exhaust manifold and even more so placing a small yet quick-to-heat-up converter directly at the exhaust manifold. The small converter handles the start-up emissions, which allows enough time for the larger main converter to heat up. Further improvements can be realised in many ways,  including electric heating, thermal battery, chemical reaction preheating, flame heating and superinsulation.
caption: Steam from tailpipe of cold car
exif: {"Image ImageDescription": "KONICA MINOLTA DIGITAL CAMERA", "Image Make": "KONICA MINOLTA", "Image Model": "DiMAGE Z20", "Image Orientation": "0", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "DiMAGE Z20 Ver1.00", "Image DateTime": "2006:01:28 07:39:16", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "311", "Image PrintIM": "[80, 114, 105, 110, 116, 73, 77, 0, 48, 50, 53, 48, 0, 0, 4, 0, 1, 0, 22, 0, 22, 0, 2, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0]", "EXIF ExposureTime": "1/100", "EXIF FNumber": "16/5", "EXIF ExposureProgram": "Program Action", "EXIF ISOSpeedRatings": "160", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2006:01:28 07:39:16", "EXIF DateTimeDigitized": "2006:01:28 07:39:16", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "2", "EXIF BrightnessValue": "23/5", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "67/20", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "48", "EXIF SubjectArea": "[1280, 960, 2560, 1920]", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "1600", "EXIF ExifImageLength": "1200", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "1818", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0", "EXIF FocalLengthIn35mmFilm": "290", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "Low gain up", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "3"}