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Clean Dry Air and Zero grade air are used for both dilution and analyzer support gas in exhaust gas analysis for emission testing. Variation in the oxygen content can make a significant impact on the accuracy of test results evaluated for Super Ultra Low Emission Vehicle (SULEV) standards. “Air” is often assumed to retain a constant ratio of nitrogen and oxygen - yet typically the oxygen content is not measured on a real time continuous basis. Production, treatment and distribution methods - the compression, purification and pressure management of air, have been shown to be capable of modifying the transient oxygen concentration by more than 10%. The results of the testing performed identify the oxygen variation behavior of several components found in Zero Air systems.

As automakers begin to develop and certify vehicles that meet the California Air Resources Board LEV II and Environmental Protection Agency Tier II Regulations, emissions test cells must be designed and implemented that are capable of accurate low-level measurements. A new test cell has been installed at Ford Motor Company for use in testing vehicles that meet the stringent Partial Zero Emission Vehicle tailpipe requirements (NMOG = 10 mg/mile, NOx = 20 mg/mile). This test cell includes a redesigned Bag Mini-Diluter (BMD), improved analytical benches, an ultrasonic exhaust flow meter with an integrated tailpipe pressure control system, a conventional constant volume sampler (CVS), and a moveable electric dynamometer. The Bag Mini-Diluter will be used as the primary sampling system for the tailpipe measurements. The moveable electric dynamometer enables the test cell to be configured so that the vehicle is moved to the test equipment rather than moving the test equipment to the vehicle.