Which pollutants are primarily measured during a Smog Check?

During a Smog Check, the primary pollutants that are measured include Hydrocarbons (HC), Carbon Monoxide (CO), and Nitrogen Oxides (NOx). These pollutants are significant contributors to smog formation and are regulated to ensure that vehicles meet emissions standards.

Hydrocarbons are a group of organic chemicals that can contribute to the formation of ground-level ozone, which is a major component of smog. Carbon Monoxide is a colorless, odorless gas produced by incomplete combustion of fuel, and it is harmful to human health, particularly in urban areas with high vehicle density. Nitrogen Oxides are produced during high-temperature combustion processes and play a crucial role in the formation of smog and respiratory issues.

The other choices include pollutants that are either not the primary focus of Smog Checks or do not directly contribute to the same extent to smog formation in the context of vehicle emissions. For instance, while sulfur dioxide plays a role in other environmental issues like acid rain, it is not primarily measured during Smog Checks for vehicles. Similarly, particulate matter and ozone are critical for air quality assessments but are measured differently outside the vehicle testing framework.