What’s the Deal With Catalytic Converters?

By Angela Monroe - September 7, 2021

What’s the Deal With Catalytic Converters H1

Catalytic converters, aka cats, are a hot topic in the car world. But what are they? How do they work? And, why are they so important?

Here are the answers.

Firstly, what is a catalytic converter?

A catalytic converter is an emission control device located within a car’s exhaust system. A noticeable bulge towards the rear of the exhaust pipe, the catalytic converter converts harmful gases into less harmful ones.

To do this, they use specific compounds to create a chemical reaction which converts dangerous carbon monoxide into less-harmful carbon dioxide. Additionally, they fight nitrogen oxide as well.

All petrol and diesel vehicles have cats fitted as per regulations introduced in Australia in 1986.

catalytic converter

How do catalytic converters make toxic gases safe?

In essence, the ‘cat’s’ job is to speed up the process of breaking down harmful molecules in exhaust gas into relatively harmless ones.

Catalytic converters use a ‘catalyst’, in the form of specific elements, to ‘convert’ these gases.

In cats, the catalysts are elements that can trigger a chemical reaction without being affected themselves.

These elements are;

Palladium – a rare silvery-white chemical element. It’s also used in electronics, fuel cells and hydrogen purification.

It can convert as much as 90% of a car’s harmful gases into less harmful ones.

Rhodium – an extremely rare chemical element. It is one of the rarest and most valuable precious metals out there. 80% of world rhodium production is used in catalytic converters.

At the time of writing;

  • Gold price per gram: A$79
  • Palladium price per gram: A$105
  • Rhodium price per gram: A$522

That means rhodium is around 560% MORE expensive than gold!

But back to the work of catalytic converters.


Using the above mentioned elements, cats convert the following gases;

Nitrogen oxide – a harmful gas that causes damage to human respiratory systems, increases the severity of asthma and can cause chronic lung disease.

In the catalytic converter, nitrogen oxide is broken down by removing nitrogen atoms from the nitrogen oxide molecules. This lets the oxygen atoms become oxygen gas – no pain there.

The nitrogen atoms form nitrogen gas. This is only dangerous in high concentration which isn’t the case when it comes out of a car’s exhaust.

This is done with the rhodium catalyst.

Carbon monoxide – a very harmful gas that is colorless, odorless, tasteless, and non-irritating which means the early signs of poisoning are difficult to detect.

The gas attaches to red blood cells, meaning they carry carbon monoxide instead of oxygen. This can lead to serious tissue damage and even death.

In a catalytic converter, oxygen atoms are added to break carbon monoxide down into less-harmful carbon dioxide and water.

Carbon dioxide is a colorless and odorless gas that quickly dissipates throughout the atmosphere. It can be dangerous in high concentration in confined spaces – which usually isn’t the case from a car’s exhaust.

This process is done with the palladium catalyst.

To recap the catalytic converter’s job

Harmful Gas From Engine > Catalyst Element > Less-Harmful Gas At Exhaust
Nitrogen oxide Rhodium  Nitrogen gas / oxygen gas
Carbon monoxide Palladium  Carbon dioxide / water

Cat burglars

When you have precious metals (worth more than gold), thieves get interested.

There’s been a rise in catalytic converter theft all over the world in recent years. Criminals are able to saw through a car’s exhaust pipes, often with battery-powered hacksaws, to remove the cat.

They then sell the units to recyclers or even as spare parts. Catalytic converters can range from a few hundred to well over a thousand dollars to replace.

There have even been reports of catalytic converters being stolen while owners are in a shopping centre.

Vehicles at risk

Hybrid vehicles typically have cleaner cats as they don’t have as many fumes passing through them. This is even more so the case on newer vehicles.

Vehicles with higher ground clearance can also be more at risk as they allow criminals room to maneuver tools underneath.

For example, a relatively new hybrid SUV parked in a dark, rarely visited area might be at higher risk.

Keep your cat safe

Try to park in well-lit areas where sounds can be heard by people. This deters thieves due to the sound that sawing through an exhaust pipe makes.

CCTV and/or a locked garage are the best options for most car owners.

Life without cats


If your catalytic converter is stolen, you’ll know. Your car’s engine will be dramatically louder, especially upon acceleration.

Furthermore, you’ll likely get a check engine light or other warning light.

If no cars had catalytic converters installed, things would be much worse.

These devices hugely reduce pollution – the visible kind and the dangerous kind.

With no catalytic converters, our cities would be much hazier and smoggier. Buildings near busy roads would have dark stains on them too.

Worse still are the health effects. Without cats, air pollution would be a much more serious issue, even here in Australia where we have relatively clean air.

Walking around a busy underground car park at a shopping centre, for example, could pose serious health risks without catalytic converters.

Angela Monroe
Angela Monroe is the Community Manager at The Positive Group, specialising in giving people the information that they need when they need it, and putting you on the path to a fair financial future. She has 8 years of experience in helping Australians find the right finance solutions, and regularly contributes articles to empower Australians with the knowledge they need to become financially healthy.


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