Do not park your car over tall grass or piles of dry leaves. Your catalytic converter gets very hot (which is normal), and it is hot enough to start a fire in the dry grass and leaves.
The catalytic converter beneath your car is part of the automobile exhaust system. It converts harmful compounds in exhaust into harmless compounds. In a typical passenger car, the catalytic converter, which is similar in shape to your muffler, is between the engine and the muffler. The unit relies on receiving the proper mix of exhaust gases at the proper temperature. Any additives or malfunctions that cause the mixture or the temperature of the exhaust gases to change reduce the effectiveness and life of the catalytic converter.
Catalytic converters have been standard on U.S. automobiles since the mid-1970s. The catalytic converter helped push toward the exclusive use of "unleaded gasoline". Leaded gasoline contaminates the catalyst used inside a catalytic converter, destroying its usefulness and leading to a clogged converter.
After the engine exhaust gases pass through the catalytic converter, the gases go through the muffler. Some vehicles use a pre-converter as well, to perform a similar function. The catalytic converter generally lasts the life of the vehicle, actually it is rare to experience a problem with it being clogged or plugged or poisoned, during its lifetime.
The inside of the catalytic converter resembles a bee hive with tunnels and passage ways coated with catalysts. There are many passages for the exhaust gases to flow, allowing for a maximum amount of surface area for the hot gases to pass.
Catalytic converters become useless in the presence of lead due to catalyst poisoning. Catalytic converters must only be run on unleaded gasoline. Catalyst poisoning occurs when a chemical in the engine exhaust coats the surface of the catalyst, preventing further exhaust access to the catalytic materials. Poisoning can sometimes be reversed by running the engine under a very heavy load for an extended period of time to raise exhaust gas temperature Common catalyst poisons are lead, sulfur, zinc, manganese, silicon and phosphorus.
Removal of sulfur from a catalyst surface by running heated exhaust gases over the catalyst surface is often successful; however, removal of lead deposits in this manner is usually not possible because of lead's high boiling point. In particularly bad cases of catalyst poisoning by lead, the catalytic converter can actually become completely plugged with lead residue.
Of late, the theft of converters has skyrocketed, due to the precious (Platinum, Palladium and Rhodium) metals used in the production of the converters. Unfortunately, the units are easily removed, especially on SUV's, which are easy to crawl underneath for quick removal of the unit.
As to being able to tell of your catalytic converter is functioning properly, the only way to find out if a catalytic converter is malfunctioning (plugged) is to remove it and check the change in engine performance, this of course being done by a mechanic. Although, sometimes you can tell that a converter is clogged because your car will not go any faster when you push the gas pedal. Also, there usually is a noticeable drop in gas mileage associated with a clogged catalytic converter.