List of Instruments in Measuring Emission

by Erin Moseley

Vehicles generate potentially harmful and toxic emissions through their exhaust pipes, especially when they are not properly maintained. Many states require that vehicles pass emissions testing before they are deemed road-worthy. Special instrumentation is used to analyze emissions and detect gases like nitrogen oxides (NOx), carbon dioxide (CO2), carbon monoxide (CO) and hydrocarbons (HC).

5-Gas Analyzers

Gas pipe exhaust is measured using special equipment such as the range of DyneSystem five-gas portable analyzers. These instruments test and measure the amount of engine exhaust for specific gas components, including CO, CO2, NO, HC and oxygen. Equipment is first calibrated using ambient air prior to each use to ensure accurate measurements. Analyzers feature a sample line to collect exhaust gases and a two-stage filter system that is capable of detecting and capturing both large and small particles. Systems have touch-screen interfaces that offer control over manual operations. Wall-mounted enclosures are optional equipment to house instruments when not in use.


A dynamometer is an electronic roller device used inside vehicle inspection bays to measure tailpipe emissions. The test vehicle is driven onto the dynamometer rollers and then testing begins. This instrument simulates the actual exhaust that the vehicle produces while in driving at low speed (15 mph) and when accelerating, all while still sitting in the bay. It's used in conjunction with a five-gas analyzer for instant data readout.

Scanning Tools

Many vehicles manufactured post-1980, and all models manufactured after 1996 have some form of on-board computerized diagnostic systems (OBDs). These computers can monitor vehicular subsystems like exhaust sensors and oxygen sensors. Scanning tools developed to exploit OBD technology can be readily connected to these on-board computers to test emissions. Hand-held electronic scanning instruments can provide real-time assessments when measuring vehicular emissions.

Gas Cap Testing

Gas cap testing checks for leaks from around vehicle gas cap seals. Invisible gasoline or diesel fumes are volatile gases and seepage into the atmosphere may go otherwise undetected if inspections are not made. According to the Illinois Environmental Protection Agency, about 40 percent of hydrocarbon emissions in the air is due to evaporation of gasoline from leaky gas caps. The instrument used for testing consists of a short, wide tube with a pressurized gauge attached. One end of the tube connects to the uncovered gas cap on the vehicle, and the gas cap that was removed is screwed onto the other end. Pressure is applied and the reading on the gauge reveals any leaks.

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