What are the three indicators for exhaust emission testing?
3 Answers
For gasoline vehicles, the HC emission standards for Euro I, Euro II, Euro III, and Euro IV are 1.1%, 1.1%, 0.66%, and 0.46% respectively. Below is relevant information about exhaust emission testing: Introduction: This involves the analysis and measurement of the composition and concentration of exhaust gases emitted by motor vehicles during idling or operating conditions, either on-site or on a test bench. Additional Items: For gasoline vehicles, fuel evaporation testing has been added, along with adjustments to pollutant emission limits. For diesel vehicles, nitrogen oxide emission limits and measurement methods have been introduced, and soot emission limits have been adjusted; requirements regarding compression ignition engines and type approval for newly manufactured vehicles have been removed.
When I first started driving on my own, I was completely clueless about exhaust emissions testing, but later learned about the three main indicators: carbon monoxide, hydrocarbons, and nitrogen oxides. Carbon monoxide is that colorless, odorless gas that can cause headaches or suffocation at high concentrations, mainly produced when the engine burns incompletely; hydrocarbons are the unburned fuel components, often leading to smog or unpleasant odors, indicating poor combustion efficiency in the vehicle; nitrogen oxides can easily trigger respiratory issues and exacerbate urban pollution like smog. Testing these is to ensure the vehicle is environmentally friendly and safe for the road. If the levels exceed the standards, it will definitely fail the annual inspection, so I always check the ignition system and air filter during every maintenance.
I've been on the road for over a decade, dealing with annual exhaust emissions testing. There are three key indicators: CO (carbon monoxide), HC (hydrocarbons), and NOx (nitrogen oxides). High CO levels indicate incomplete engine combustion, possibly due to a clogged carburetor; excessive HC emissions result in black smoke, signaling aged spark plugs or fuel injectors; NOx issues are common in older vehicles, with yellowish exhaust emissions, and regulations are quite strict. I recall one instance when NOx levels exceeded the limit, and the mechanic had me replace the catalytic converter to resolve it. Keeping these indicators in check ensures smooth and eco-friendly driving—the key is diligent routine maintenance.
