Air Filters in Automotive: Type and Function

The anatomy of the human body and an automobile are quite similar when it comes to the requirement for air. We need it for breathing; a car needs it for combustion.

To function optimally, a car engine requires hundreds of cubic metres of air. However, the air within the cabin and used by a car engine must be free of any impurities. Both of these are taken care of by air filters on the intake system of automobile engines and the ventilation system.

Keep scrolling to understand what car air filters are, their different types, their purposes and more.

Automotive air filters take care of the air quality and quantity used by a car engine and the air quality within the cabin. They primarily maintain an optimum airflow to enhance the overall engine performance and keep the cabin free of dust, pollen and other air pollutants.

You can find them in different shapes, including cylindrical, panel-like or circular and are made of synthetic paper or foam, cotton or a pleated material for maximum filtration.

Modern cars commonly come with two types of air filters, depending on the functionality. They are:

1. Cabin Air Filter

This rectangular-shaped small pleated filter is a component of the ventilation system. It is made of multi-fibre paper cotton or other material and is located under the dash, instrument panel, or hood behind the glove compartment. 

It has four types:

• Charcoal Cabin Air Filter

It features a porous material and an extra carbon layer to accelerate the absorption of any microscopic pollutant. Moreover, it tackles gaseous toxins like exhaust fumes and smoke.

• Particulate Cabin Air Filter

This also comprises a porous fibre capable of trapping particles as tiny as 0.3 microns. It is the most basic type used in most cars.

• Electrostatic Cabin Air Filter 

It is the most efficient of the lot since it uses static charge to capture ultra-fine particles. The layers of electrostatically charged material activate as the air flows through them. Moreover, it takes care of the musty or mouldy odours inside the cabin.

• Activated Carbon Filter

It is similar to a particulate filter but has an additional layer of specially activated carbon or charcoal. Such carbon has high absorption efficiency for gaseous contaminants such as carbon monoxide. Additionally, it traps bacteria and other similar micro-organisms.

2. Engine Air filter:

This air filter is an essential part of the combustion system. You can find it under the hood and open it by releasing the latches or tabs with your hands, a socket set, or a screwdriver.

These air filters can be categorised into three types based on the material they are made of:

• Paper Engine Air Filters:

These are the most common types for being affordable, reusable and replaceable. However, it is primarily used in small cars for regions with low pollution levels. 

• Gauze Engine Air Filters:

Further classified into two categories- oiled gauze and synthetic gauze, these are long-lasting and can be cleaned easily.

• Foam Engine Air Filters:

It serves as an additional layer of protection to keep any dirt or debris away from a car’s combustion system.

Let us understand the function of cabin and engine air filters individually.

1. Functions of Cabin Air Filter

Also known as a car pollen filter, it is a vital component of the Heating, Ventilation and Air Conditioning System (HVAC). Before air moves inside the cabin of your car, it goes through this filter which:

• Prevents Allergen Build-up:

The filter traps all sorts of contaminants, including bacteria, viruses, mould spores, dust, debris, pollen, pet fur, and the toxins of exhaust gases. This way, it prevents harmful pollutants, keeping the cabin clean.

• Ensures Optimum Air-conditioning:

It maintains the efficiency of the AC system by keeping the pollutants away. A clogged cabin air filter causes reduced airflow, foul smells from the vents and fogged windows. These may cause the blower motor to need more power to perform, disrupting mileage.

2. Functions of Engine Air Filter

Located under the hood on the top or side of the engine, a fully working air filter: 

• Lowers emissions

It maintains the airflow to the engine since polluted air is a prime reason behind faulty spark plugs. It controls engine depositions and the exhaust emission levels in check. 

• Improves fuel economy

A car engine requires over 10,000 litres of oxygen to burn one litre of fuel. In this respect, an engine air filter ensures optimum airflow quality and quantity, enhancing acceleration.

• Increases engine’s life

A perfectly working engine air filter prevents even the tiniest particle, as small as a grain of salt, from entering the internal engine components like valves, cylinders and pistons. This keeps the engine's health and performance in check. 

Though the purpose of the cabin and engine air filters are the same, their mechanism is different. 

Here's a detailed overview of how the different car air filters work.

1. How Does a Cabin Air Filter Work?

After you close your car's windows, the air enters the cabin through the ventilation system. Now, the air passes through the ventilation system to the vent, heater, defroster and air conditioner.

Nonetheless, before entering the air conditioning and heating housings, the air flows through the cabin filter to trap allergens and similar substances without hampering the airflow. 

2. How Does an Engine Air Filter Work?

Engines require air for the combustion process. The cold-air intake tube in the fender, grille, or hood scoop pulls air from the atmosphere into the engine manifold. 

Before entering an engine, this air passes through the engine filter. All unwanted particles get trapped inside this filter medium and separate from the passing cleaner air at that stage. 

Next, these particles form a layer on the upstream side of the filter medium to screen for other pollutants. This way, an engine air filter maintains an optimum airflow level in a car's engine.

Over time, air filters get clogged and trigger several vehicular concerns that may cost hefty repair and replacement bills. Such circumstances call for an immediate replacement service. However, though quick and affordable, given an extensive range of options available, you must pick an Original Equipment Manufacturer (OEM) product for your car. For that, check your car's owner's manual to determine its type and location as per your vehicle model.