What substance is commonly tested for in vehicle emissions?

Carbon monoxide (CO) is commonly tested for in vehicle emissions because it is a harmful byproduct of incomplete combustion of fossil fuels, which occurs in gasoline and diesel engines. The presence of carbon monoxide in vehicle emissions is a significant environmental concern, as it can contribute to air pollution and negatively impact public health. High levels of CO can lead to harmful effects such as headaches, dizziness, and at higher exposures, it can be lethal.

Testing for carbon monoxide in vehicle emissions is a critical part of emissions regulation and vehicle inspection programs aimed at reducing air pollution and ensuring that vehicles meet environmental standards. Understanding the concentration of CO in emissions helps regulatory bodies enforce limits and encourages manufacturers to improve vehicle technology for cleaner emissions.

In contrast, while nitrogen dioxide, ozone, and hydrogen are also relevant in discussions about air quality and emissions, carbon monoxide remains a primary focus for vehicle emissions testing due to its immediate health risks related to vehicular exhaust.