What Are The Different Types of Filters?

We come across filters every day in one form or another. Now and then, we come across them in obvious locations; other times, they hide inside different pieces. Generally, filters were developed to enable total removal of impurities like sediments, dirt, electromagnetic interference, bacteria, and chemicals among fluids.

Some people believe that filters are only used in decontaminating gases and fluid, but it's far from the complete truth. With the growth and advancement of modern technologies, filters can discard things as complex as optical and electrical problems. In this article, we'll examine a list of varying filters and where you might likely need them.

What are the types of filtration? (Types of filters)

Air Filters

The major work they do happens to be the purification of the air that flows through any medium. An air filter is a fibrous entity that eliminates gaseous and even solid impurities from incoming air. It has diverse applications, from engineering to even medicine. Industries first have to cleanse the fume-filled air they produce before letting it flow into the surroundings, to avoid a severe health crisis.

This equipment comes in diverse forms and dimensions, and it is dependent on the features of the machine they fit into possesses. Air filters discard varying impurities like exhausts, lubricants, germs, and dirt.

An air filter comprises basically of two parts – a filter element that is built specifically to match the equipment they fit into, and a casing that houses the filter. Vital requirements considered before assembling an air filter include the filter characteristics as well as the dimension, type, filter medium, rate at which the air flows (flow rate), and the planned use or application.

Appliances that incorporate air filters in their designs include:

  • Automobile engines.
  • Vacuum cleaners.
  • Furnaces.
  • Refrigerators.
  • Air conditioners.

Fuel Filters

This equipment is designed to fit perfectly along an engine's fuel line. Their main job happens to be the complete eradication of small particles and fluid impurities like water and oil. A standard fuel filter serves the function of getting rid of dust gathered over a while in an internal combustion engine. These filters have cartridge like designs, having the filter paper placed inside the cartridge.

Fuel filters serve a crucial purpose in eliminating rubble from an internal combustion engine. If these impurities enter the engine, they might, in a short while, cause rapid wear and tear, causing untimely fuel pump and injector failure.

The main requirement when assembling a standard fuel filter includes dimensions of the filter, filter type, filter medium, flow rate, and the planned use. Fuel filters are built with their overall dimension being a key factor in maximizing their efficiency.

Electronic Filters

Not designed like other filters, as the name implies, these pieces of apparatus are circuits whose primary purpose entails classifying series of electronic signals, discarding interfering and undesired frequencies, while enhancing the frequencies needed.

Electronic filters work best under radio frequency (RF). The range of frequencies they function in is between audio frequencies and intermediate frequency.

The primary functions for these filters include:

  •  High and low pass
  •  Analog and digital.
  •  Passive and active.

Electronic filters are also used to minimize or completely eradicate electrical sounds.

Water Filters

These types of filters are specifically designed to get rid of impurities like dust, sediments, mineral, and chemical contaminants from water supplies employing either a chemical process of filtration or a physical barrier. Often employed in purifying household water, water filters come in a wide array of different shapes and dimensions.

The main requirements for water filters include the particle's size, filter type, filter medium, water flow rate, physical specification, and the planned application. Water filters are present and used in areas like:

  • Agricultural irrigation
  • Swimming pools
  • Water resorts
  • Personal and Public aquariums
  • Fish ponds
  • Refrigerators and water dispensers
  • Wastewater companies

Microwave and RF Filters

Designed in the form of a circuit, these devices are designed with the sole purpose of either permitting or blocking certain frequencies. Primarily employed in eradicating certain frequencies and amplify others, these circuits, similar to RF filters that operate at radio frequencies, run on microwave frequencies. They work at a certain frequency range, megahertz, and gigahertz, to be precise.

Hydraulic Filters

To clean hydraulic fluids properly, you make use of hydraulic filters fitted inside hydraulic pumps and cylinders. Hydraulic cylinders have filters placed in them to clean the hydraulic oil that lubricates them. Hydraulic fluid filters remove dirt and other solid debris, ensuring that the hydraulic oil flowing in the machine is dirt and contaminant free. Dependent on the fluid to be filtered, engineers build hydraulic fluid filters with different materials to maximize their efficiency while maintaining a high overall lifespan.

Fluid Filters

We employ fluid filters in cleaning and removing solid debris, sediments, and chemical contaminants from all types of fluids. The filtration process starts when the fluid flows through the filtering elements. The contaminants are kept form flowing through, and the contaminant-free fluid flows out.

There are two parts to a standard fluid filter device. The first part would be the element that holds back the debris, and the second happens to be the filter casing. Fluid filters come in a different size, shape, and material depending on the sort of fluid and the fluid's density.

The main requirement for building a standard fluid filter includes the type, medium, contaminant dimension, fluid flow rate, and the intended application. The materials used in constructing a standard fluid filter include:

  • Filtering foam
  • Filtering cloth
  • Steel (stainless steel)
  • Carbon

Optical Filters

They convey light having various wavelengths. Placing a plastic material or specific glass plane in the light's path helps achieve this. Different color dyes coat the plastic material or glass plane used. The optical characteristics of these filters depend solely on how they respond to different frequencies that pass through them. These filters are mostly used in photography.

There are two kinds of optical filters, both having unique features – the absorptive filter and dichroic or interference filter.

The main requirements for optical filters include the type of material used, frequency response rate, filter dimension, and wavelength features. Some optical filters only allow a certain range of wavelength pass through them. These include:

  • Ultraviolet (UV)
  • Infrared
  • Bandpass

Electromagnetic Interference Filters

EMI stands for electromagnetic interference. These filters also referred to as radio-frequency filters (RFI for short), are electrical circuits that alleviate electromagnetic noise of high frequencies. The noise is usually between 9KHz to 10GHz.

The key requirement when building EMI filters includes voltage, bandwidth, current, and specified frequency.

Primarily used by them between the telecommunication or electronic device and an AC power line, EMI filters design makes it capable of protecting all types of electronic systems.

Smaller models can also go on PCBs, connectors, or stand-alone components for affixing in utility cabinets. There are various types of electromagnetic filters available, and they all possess unique wavelengths. These filters including:

  • Low pass
  • High pass
  • Bandpass
  • Reject pass

Applications of Different Filters

Liquid and gaseous filters depend heavily on some absorptive material like foam, paper, or synthetic cloths. The physical property these materials have in common is their pore size. This is to ensure that only clean fluid or gases pass through them while contaminants are held at bay.

Fuel, Air, Fluid filters are generally replaceable. They are built, having varying patterns from the spiral, to pleated, to baffled. You can buy such filters as complete accessories, or you can choose to purchase only the filtering element.

To understand the sort of filter to buy that would best match the machine, you need to first take into consideration the flow rate and the pressure drop. this is because restrictive filters drastically reduce pressure and flow rate.

Any machine that takes in the air needs an air filter to purify the air flowing into it not to clog the machine. Vacuum cleaners, combustion engines, and all types of compressors need air filters to clean the air flowing in and out of them. They need to remove dust, dirt, and other solid particles.

Compressed air systems also have built-in air filters. The unique process of air filtration is by powering a compressed mechanism.

Industries also incorporate air filters into the majority of their processes. They make use of air filters to purify the fume-filled the air before returning into the environment. This is because most industrial fumes are toxic and negatively affect humans, plants, animals, and the environment at large.

Respiratory masks have inbuilt air filters. They are developed as replaceable filter cartridges that help purify the air that the wearer breathes.

Water companies purify the water they distribute using water purifying filters. Swimming pools, refrigerators, water parks, and homes also use water purifiers too. The water filters in residential and commercial buildings are put in place to purify the water used in cooking, drinking, and showering. They remove impurities, particles, chemicals, minerals, and harmful bacteria, and supply healthy water.

Industries also employ water filters to cleanse the water that cools down various machines. They do this to avoid clogging their machines. The filtering element present in water filter varies depending on what the application may be. Charcoal, filtering cloth, sintered metals, these are some of the few valuable filtering elements used.

Combustion engines make use of cartridge styled replaceable fuel filters. These disposable filters are easy to change. Their main function is to discard oil, dirt, water, and solid particles from diesel and petrol.

Hydraulic fluid filters present in hydraulic pumps help remove particles that could clog the pumps and spoil them. They are built with the pump pressure in mind too. 100, 3000, and 6000 psi are the common pressure capacities noted when choosing hydraulic filters. They are mainly built as spin-on systems, just like those in an internal combustion engine. Industries like power plants and steel mills use hydraulic filters for their pumps.

The filters mentioned above can clean fluids, but fluid filters dissect the distinctive forms of fluid filtration. These filters can filter items such as liquid food, beverages, wines, and other subcategories.

A common application of optical filtration is seen in photography, but other things make use of optical filters. Searchlight is another prime example of a device that uses optical filters.

Electronic filters are built in circuits rather than in capsules. The military and technological companies and telecommunication industries use these filters to extinguish undesired sounds, frequencies, and signals.

It is important to note that some filters do not come with filter elements. For example, industrial-grade water filters depend on the sand for filtering the water supplied.

Reverse osmosis filtering employs high-pressure mechanisms to push water through membrane like panels forcibly. This process is unique as it is capable of removing salt from seawater.

Significant Attributes of Filter

Planned Application

Knowing where and what the filter needs to do goes a long way in selecting the right type of filter that will fit properly. You need to know the specific job you want the filter to do so you would pick the one that is best effective.


This describes the substance that is flowing through the filter. Knowing the specific substance that needs to be filtered automatically indicate what type of filter to use

Filter element

The filter element is the main equipment that does the filtrating. The filter element removes filtrates and leaves a clean flowing substance.


Filtrand is the name given to the substances that are filtered away. Filtrands include things like bacteria, grime, dirt, dust, and even chemicals and minerals in water purification. For example, taking oil as the filtrate and sand as the filtrands, the desired filter chosen would be a filter that discards sand and allows clean oil to flow through it.

Filter Types

The filter types, commonly referred to as types, decides the element to be used. For EMI filters, the different types available determines what type of signal it filters out and what type of signal it retains.

Flow Rate

The two standard units in which flow rate is measured in is:

  • cubic feet/min (cfm) for air/gas filters.
  • gallon/minute (gpm) for liquid filters.

Filter Media

Most people are not able to differentiate the filter element and the filter media, even with the knowledge they have gathered over time. The filter element refers to the materials in which the filter is created out of, while the filtering agent is referred to as the filter media. If you are looking for a specific type of filtering agent irrespective of the filter element, you would have to search the filtering agent section to find what you are looking to purchase.

In conclusion, it is a wise idea to verse yourself with the different classes of filters and their functionality. Having proper knowledge of the workings of a filter and how best to maximize them will help you keep your machines and engines in top condition.

It is essential to eliminate contaminants as they could pose a threat to hydraulic pumps, combustion engines, fuel pumps, compressors, injectors, and other equipment.

Filter buyers must be able to differentiate the different parts that they need. Whether it is the filter element or the casing, they need to ascertain which part they require and which form it should take.

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