The Air Injection System (AIS) is primarily designed to reduce which pollutants during engine warm-up?

• A. NOx and CO2
• B. HC and CO during engine warm-up
• C. NOx only
• D. HC only

Answer: (B)

The AIS works by adding fresh air into the exhaust flow during cold starts to promote oxidation of unburned fuel. That extra oxygen helps burn off hydrocarbons and carbon monoxide while the catalytic converter is still warming up, so HC and CO emissions drop during engine warm-up. While NOx can be formed at high combustion temperatures, the AIS isn’t designed to reduce NOx; it’s specifically aimed at oxidizing HC and CO, which is why the best choice is hydrocarbons and carbon monoxide during warm-up. CO2 isn’t something the AIS targets, since it’s a natural product of combustion, not a pollutant the AIS is intended to reduce.