The Colorado Department of Health (CDH) collected CO exhaust emissions data from twenty-one vehicles using three “short” emissions tests, and the Federal Test Procedure (FTP). CO data were also collected from these vehicles using a remote sensing system. Excess carbon monoxide emissions were calculated from the difference between FTP measurements and federal standards. Emissions were then categorized by individual vehicle and by vehicle type. Errors of comission and omission were determined for each of the short tests and remote sensing system.
The CDH226 showed the highest correlation for identifying vehicles emitting excessive CO. Compared to the FTP, it identified the vehicles responsible for 98.5% of all excess emissions. All the “short” tests and remote sensing tests identified the vehicles producing the majority of excess emissions. The current BAR '84 type idle “short” test and the CDH226 demonstrated the lowest errors of comission, or false failures. Both tests had zero false failures for an error of comission rate of 0%. The remote sensing test experienced a 14.3% error of comission, the highest error of comission.
In the Denver metropolitan CO nonattainment area, emissions from mobile sources account for 90% of the carbon monoxide inventory (1). Excess CO emissions, or emissions in excess of permissible standards, contribute significantly to these overall emissions. Identification of excess emissions and a reduction in those emissions is the principle behind Inspection/Maintenance (I/M) programs.
To analyze the ability of EPA approved short” tests and a remote sensing test to identify excess emissions, the Colorado Department of Health (CDH) compared data taken from: an idle mode tailpipe test, a loaded two mode short test, the mass emissions CDH 226 test (2), the remote sensing Fuel Efficiency Automobile Test (FEAT), and the Federal Test Procedure (FTP) (6). Mass emission measurements were compared to the EPA new vehicle certification standards. Concentration measurements were compared to the concentration cutpoints set for the Colorado I/M program.