| Black exhaust smoke | 8 |
| Blue exhaust smoke | 10 |
| Brake specific exhaust emission | 13 |
| Catalytic converter | 18 |
| Crankcase emissions | 4 |
| Emission reduction system | 16 |
| Engine emissions | 2 |
| Engine emission data | 14 |
| Engine emission toxicity | 15 |
| Exhaust emissions | 3 |
| Exhaust gases | 6 |
| Exhaust gas aftertreatment | 17 |
| Exhaust gas recirculation | 22 |
| Exhaust smoke | 7 |
| Exhaust smoke opacity | 11 |
| Flame afterburner | 19 |
| Fuel evaporative emissions | 5 |
| Motor vehicle emissions | 1 |
| Running exhaust emission | 12 |
| Scrubber | 21 |
| Thermal reactor | 20 |
| White exhaust smoke | 9 |