Motorist’s safety is a top priority in Texas; as a result, vehicles registered in Texas are required to pass an annual inspection to ensure compliance with safety standards. While safety inspections are required throughout the state, emissions testing is required of vehicles inspected in 17 Texas counties to comply with federally mandated clean air requirements. Vehicle inspections are performed at Official Vehicle Inspection Stations licensed by DPS.
Vehicle Emissions Inspection Types and Certified Analyzers
Descriptions of the types of vehicle emissions inspections and certified emissions testing analyzers in use in Texas by area.
Types of Vehicle Inspection
On-Board Diagnostics (OBD) II Station Only
Vehicle Emissions Inspection Types
ASM: A vehicle emissions inspection for nitrogen oxides (NOx), carbon dioxide (CO2), hydrocarbons (HC), and carbon monoxide (CO) for vehicles model-year 1995 and older. The ASM inspection uses a dynamometer (a set of rollers on which a vehicle's tires rest) which applies an increasing load or resistance to the drive train of a vehicle, thereby simulating actual tailpipe emissions of a vehicle as it is moving and accelerating. The ASM inspection is comprised of two phases:
(1) the 50/15 mode, where the vehicle is inspected on the dynamometer simulating the use of 50% of the vehicle's available horsepower at a constant speed of 15 mph and
(2) the 25/25 mode, where the vehicle is inspected on the dynamometer simulating the use of 25% of the vehicle's available horsepower at a constant speed of 25 mph.
OBD: Computer system installed in a vehicle by the manufacturer which monitors the performance of the emission control equipment, fuel metering system, and ignition system. The OBD system detects malfunction or deterioration in performance of components that would cause the vehicle not to meet emissions standards.
TSI: A vehicle emission inspection for CO2, HC, and CO for vehicles model-year 1995 and older. The TSI inspection is an idle inspection comprised of two phases:
(1) a high speed inspection at 2,200-2800 revolutions per minute (RPM) and
(2) an idle inspection at 350-1,200 RPM.