What does catalytic converters do?

Reduces the toxicity of internal combustion engine exhaust. It uses a catalyst and a chemical reaction to convert toxic combustion by products into a less toxic substance.
A catalytic converter takes the exhaust gas stream from the engine and breaks the noxious components of the exhaust down to less noxious or harmless components.

== Answer == To reduce auto emissions.
== Answer == The catalyst in a catalytic converter causes unburned hydrocarbons to oxidize. To do so, oxygen must be present in the exhaust mixture. If an engine is running well, there isn't really much for the catalytic converter to do. If the engine is in need of a tune-up, the catalytic converter may get quite a workout and in the process it can get very hot. Also, deposits can build up on a catalytic converter, making it useless. If the engine is running poorly, and a lot of unburned fuel is going out the exhaust, deposits from the fuel can build up on the catalyst. If the engine is burning oil, oil deposits can also build up.
It converts carbon monoxide, which is very deadly to all animals into carbon dioxide, which is not near as bad for the environment and it also helps prevent greenhouse gases because of this.