Emissions standards are regulations set by governments to limit the amount of pollutants that can be released into the air from various sources, such as vehicles and industrial facilities. These standards aim to protect public health and the environment by reducing harmful substances like carbon monoxide, nitrogen oxides, and particulate matter. Different countries and regions have their own specific emissions standards, which can vary based on the type of source and the pollutants involved. For example, the Environmental Protection Agency (EPA) in the United States establishes standards for automobiles and power plants to ensure they operate within safe limits for air quality.