Find out more about catalytic converters
Many states and localities have legislated annual automobile emissions testing that checks the actual emissions content. It's illegal in some states and localities to remove a factory-installed catalytic converter. A mechanic can sometimes temporarily remove it and replace the catalytic converter with a test pipe, but the rules on this can vary from place to place.
This kind of device which is attached to vehicles became a major advancement and helpful to citizens in the country because it can help the governments resolve their environmental problems such as addressing air pollution.This kind of device is very helpful to countries where air pollution is a pressing problem. This is now widely used in large countries such as the United States of America.