What is the Emission System? –  Emission System Components in Modern Cars

Do you ever go out and realize what we have done to this world? The last time the world was cleaner was during the time of lockdowns. Everything was closed, including industries, retail businesses, and cars were parked in garages. You will be surprised to know that the Air Quality Index (AQI) score dropped significantly within a month during that time. The rivers got cleaner. The trees were greener, it was something that nobody had witnessed in the near past years. Don’t you wish to live in that environment without being locked in at home?

We can definitely make the world better again if we minimize the sources of harmful pollutants and emissions. Our vehicles are one of the major sources of those toxic pollutants damaging our environment and emission control systems are designed to keep that low. Let’s get into the details of ‘what is the emission system’, ‘evaporative emission system’ and ‘what is the purpose of an exhaust emission system’.

What is the Emission System in a Car?

The emission system of a vehicle ensures the smooth performance of the vehicle without releasing excessive output. It performs a series of functions in order to keep the discharge of toxic gases as low as possible. To be precise, it controls the emission of gases like carbon monoxide (CO), nitrogen oxide (NOx) and Hydrocarbons (HC).

Due to tech advancements, automotive engines have become much more advanced. The latest technologies have helped reduce the emission output with minimal advancements. For instance, using the right air/fuel ratio, efficient combustion techniques, variable fuel ratio, etc.

What is the Main Purpose of an Exhaust Emission System?

What is the Main Purpose of an Exhaust Emission System

An emission control system in vehicles is deployed to control the release of toxic gases from the internal combustion system and other components. The primary sources of toxic gasses include fuel tanks, crankcases, and carburetors.

An emission control system is mainly designed to control that in order to make the environment cleaner and safer for everyone. In the absence of this system, car pollution would be much worse and pose a greater threat to humans.

Factors that Affect a Car’s Emission System

Following are some factors that can be detrimental to a car’s emission system. They include:

  • Atmospheric conditions and driving.
  • Mileage
  • Vehicle age
  • Material of electrode in a spark plug
  • Bad vehicle maintenance
  • Bad quality fuel
  • Damaged sensors
  • Cracked or dry-rotted vacuum hoses

Next, we have discussed more impactful and essential emission control methods that we must comply with rigid emission norms as well as revealed several other components of the emission system.

What are Catalytic Converters in the Emission System?

What are Catalytic Converters in the Emission System

Catalytic converters are an integral part of your car’s emission system located close to the engine upstream of the muffler. Its main purpose is to convert toxic gases into more benign ones. While they have been used since the 1970s, drastic improvements have been made to them to improve their efficiency.

There are two types of catalytic converters, two-way and three-way. The former can only control the emission of HC and CO while the latter can also minimize the release of NOx and thereby, it is used in most modern cars. It comes in a cylindrical canister shape fixed on the exhaust pipe. It comprises some valuable metals like Palladium (Pd), platinum (Pt), and Rhodium (Rh) to carry out the oxidation process and convert extremely damaging gases into Carbon dioxide and water.

What is the Evaporative Emission System?

What is the Evaporative Emission System

The evaporative emission system in a car is made to store and release fuel vapors before they are emitted into the environment. Not just it help achieve fuel efficiency, but it keeps that weird gasoline smell out of your car’s cabin. It controls the emission and evaporation of hydrocarbons from a vehicle’s fuel tank and transmits them into the combustion chamber.

A carbon canister is the key component of the emission system as it stores hydrocarbons, absorbs fuel vapors, and discharges them through the purge solenoid.

What does Exhaust Gas Recirculation (EGR) do?

What does Exhaust Gas Recirculation (EGR) do

Exhaust Gas Recirculation (EGR) is an advanced emission control technology that lowers emissions and keeps the engine’s temperature cool.  While petrol engines had adopted this technology far earlier, it is now available with diesel and turbocharged petrol engines.

Talking about the working mechanism, it returns some amount of exhaust gas to the vehicle’s combustion chambers via the intake manifold to lower the temperature inside and eventually reduce the emission of NOx.

What is Diesel Particulate Filter (DPF)?

What is Diesel Particulate Filter (DPF)

A Diesel Particulate Filter (DPF) is a part of a car’s emission system and helps capture and store soot traps or exhaust sots to minimize the harmful emissions from diesel cars. However, since they have limited capacity, the trapped soot must be emptied periodically to regenerate the DPF.

Check out the best diesel engine suggestions by car experts.

What’s the role of Selective Catalyst Reduction (SCR)?

Selective Catalyst Reduction (SCR) provides means to convert NOx gas into diatomic nitrogen and water with the help of a catalyst. It is categorized under the advanced method of emission control and is typically used in higher-capacity diesel engines. SCR, also known as Adblue, is a type of liquid urea that works jointly with the DPF to control the discharge of Nitrogen gas. The converter nitrogen gas is less harmful than NOx and released from the exhaust pipe.

It is due to the presence of SCR that modern vehicles are capable of minimizing NOx by 90%.


That is how complex an emission control system is. It requires several components working simultaneously to perform with full efficiency. Moreover, it needs proper maintenance and routine visits to continue operating well because even a single damaged part or poor care can affect its performance and eventually lead to bigger problems.

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