What is a Pre-Filter? Does My Air Purifier Need a Pre-Filter?

What is a Pre-Filter, and Does My Air Purifier Need a Pre-Filter? 

What Is A Pre Filter

By now, you’ve probably learned what an air purifier does, and, odds are, you’ve found some units which have a “pre-filter”, but you may not know what a pre-filter is. What is a pre filtrer? A pre-filter is a filter that captures large particles from the air before they clog your main filter, which is commonly costlier than the pre-filter, and meant to deal with smaller particles. Pre-filters serve to save you money over the long term, which can more than make up for their cost.

A pre-filter is generally an affordable, or washable filter which is utilized in some air purifiers to maximize your main filter’s lifespan. We recommend purchasing an air purifier with a pre-filter simply because of the fact that they can save you money over the long run. They are not required, but they extend the life of your main filter, which means your air will be cleaner, for a longer time. 

Today, we will share with you what a pre-filter is, what they do, and why they are important. Many air cleaning models come with a standard pre-filter simply because of how beneficial they are.

What Is A Pre Filter

Right off the bat, let’s address the question “What is a pre-filter?” 

A pre-filter is, quite literally, a filter that comes before your main filter. Meaning the air that your air purifier is cleaning has to travel through this pre-filter before it can get all the way to your more delicate main filter, like a HEPA filter. 

Pre-filters are commonly made of materials that are either cheap and disposable or (more commonly) they are made of a more durable and washable material. More often than not, a pre-filter will have a very long lifespan because they are made to be cleaned, rather than thrown out. This is different than most air filters on the market, including HEPA filters. Read on below for information on the different types of pre-filters!

Because your pre-filter is the front-line against all of the filth in your air, it has been specially designed for the job. But, what is all-important this job?

Extend The Life Of Your Main Filter

A pre-filter’s purpose is to maximize the lifespan of your main filter, which can prove to save you a lot of money over the life of your air purifier. Your main filter is commonly one of the more expensive pieces on your air purifier, and they need replacing every so often. These filters generally range from rather inexpensive, to moderately expensive, and their replacement schedules can vary greatly. 

Generally, air purifiers that have pre-filters utilize a HEPA filter, or a comparable filter, which is made to filter out some of the smallest particles out there. Some HEPA filters only last several weeks, while others last several months. Across the board, the best way to get the longest lifespan out of your main filter is to get an air purifier that has a pre-filter. 

HEPA filters, among the various other filters you’ll find out there, are what make air purifiers useful. A pre-filter serves to increase the lifespan of these costlier filters. Check out our article on the importance of air filters to learn more about them! You’ll learn a lot, including the fact that there are several different levels of HEPA filters out there!

What is a pre filter? Pre-filters sift out the largest particles which will be running through your air purifier, which leaves the smallest particles to your HEPA filter. These large particulates in the air include things like pet fur, dust, and a lot of the other things you can see floating around in the air.

If all of these particles get sucked directly into your HEPA filter (rather than the pre-filter), then your HEPA filter’s effectiveness and lifespan will be greatly reduced, making the pre-filter invaluable. 

Pre-filters are ideal for people who have issues with pet fur, as they will save you a lot of money in the long run. Check out our article on the best air purifier for pet owners to see what else your air purifier will need! We will also share why certain filters are needed, and more!


Wash them as necessary, if you run your air purifier around the clock, then it is recommended to wash your filter at least once a month. Generally, all of the washing that these filters will require is a quick vacuuming to rid the filter of all of the particles it has collected. More often than not, you’ll be able to see the improvement between when you started with a dirty pre-filter, and when you finish. 

Not all manufacturers make a pre-filter which can be vacuumed. Some may need rinsed with water, or cleaned in some other way. Not all pre-filters are washable either, so it is best to follow the procedures laid out by the manufacturer of your specific unit. 

Even if you treat your pre-filter perfectly, and clean them well, they will still wear out some point. Some pre-filters can last decades (namely the screens), while most will likely last just a decade or so, depending upon how much they are used. Regardless, these filters with the shorter lifespans are generally rather cheap to replace. 


pre filter

One of the most common types of pre-filter looks a lot like your standard filter, and it is commonly made out of either a fabric or paper product. These filters can usually be vacuumed clean. A less common, but still very good type of filter is a grid or screen which captures larger particles out of the air. Some air purifiers may also utilize a spongy-looking pre-filter which is very effective. 

Fewer air cleaning units utilize a static-charged collection grid, which has one of the longest pre-filter lifetimes. These static grids work very well but are commonly a lot more expensive than the other types of pre-filters, which makes them less desirable. 

Some air purifiers even utilize specialized pre-filters which may include activated carbon, which can be an invaluable extra. However, the drawback to some of these filters is that they may, in fact, need replaced.

This can result in an added expense, which may be a drawback to such a design. However, there are many air purifiers on the market which have a separate pre-filter and carbon filters. This means that you can have the best of both worlds, namely a washable pre-filter that won’t need to be replaced, in addition to a separate carbon filter.

What is a Pre-Filter? Does My Air Purifier Need a Pre-Filter? 1

Here’s an air purifier that we love that’s super cheap and has a pre-filter of sorts, and a HEPA filter AND an activated carbon filter!

It has a little bit of everything and costs less than a meal at a fancier restaurant.

Check it out here!

And, if you’ve already bought one, or if you’re thinking about it, you can get replacements for your main filter here.


HEPA filters are made to meet rigorous standards set in place by both European and US governments. These standards ensure that your HEPA filter lives up to its name: High-Efficiency Particle Arresting (HEPA) filter. 

These standards ensure that the HEPA filter (which has several different levels) truly sifts out some of the smallest particles in the air (all the way down to .3 microns) while cleaning the air of more than 99.9% of the particulates from the air that passes through it. This makes these particular filters a lot costlier than normal filters which don’t do nearly as good of a job at cleaning the air. 

Your pre-filter, on the other hand, does not have to follow such stringent guidelines. Essentially, all they have to be is a filter that comes before your main filter. This shouldn’t be anything to worry about, however, as a pre-filter’s job is easy. All they need to do is stop large things from clogging up your main filter. 

Because of this nuance, there are countless different kinds of pre-filters on the market, as we previously have covered. They may work in different ways, but at the end of the day, they do the same job. 

More often than not, companies will put in a cheap fabric filter, paper filter, or screen which is easy to manufacture and serves its purpose very well. Most of these filters, despite being cheap, are still rather durable, and will likely last years. When it comes time to replace them, their price point will likely be nothing to balk at. 


Yes, pre-filters can help with cleaning some dust out of the air, but they shouldn’t be your only filter. By definition, pre-filters come before your air purifier’s main filter. They can’t sift out all of the dust in the air (again, that’s what your main filter is for), but they do capture larger particles of dust. This includes dust bunnies, hair, and generally just larger visible particulates. 

If you are in the market for an air purifier that captures dust effectively, check out our article “Do Air Purifiers Reduce Dust?” This article will walk you through how they work at cutting down on the amount of dust in your home. 

Just about every air purifier on the market can reduce the amount of dust in the air. Some are a lot more effective than others at doing this. However, air purifiers come in at countless different price points, many of which are outside of a lot of people’s budgets. Check out our article on finding an affordable air purifier worth buying, since not every cheap unit is worth your hard-earned money!

Air purifiers come in all shapes and sizes. Some are personal and portable, while others can take care of massive buildings. They also address a large variety of air quality issues that you may want to see fixed in your own home. If dust is the only thing you want to be fixed, then you can purchase some really cheap air purifiers that’ll do that very well. 

One air purifier that we find works great at reducing dust at a very low price point actually uses water as it’s filter! This means you won’t have to purchase expensive replacement filters every so often, instead, you just need to change out your unit’s water. These units don’t usually need a pre-filter, but some units do have them. Some water-based air purifiers even use the water as a pre-filter, which is interesting. 

To learn more about water-based air purifiers, visit one of our posts on them! They answer questions like what water-based air purifiers do, and what water-based air purifiers are. These air purifiers aren’t as effective as their more expensive counterparts (i.e. units with HEPA filter), but at their price point, they are great. They also can double as oil diffusers, and even can work as a light humidifier! 

What is a Pre-Filter? Does My Air Purifier Need a Pre-Filter? 2

Here’s another air purifier that has a pre-filter, HEPA filter, and activated carbon filter. Its pre-filter is washable, and you can get different color ones to change the color of your machine if you want!

Check it out here.

Frequently Asked Questions

Why Should I Buy an Air Purifier?

Why shouldn’t you? (We jest)

This truly depends on where you live, and your health needs. We highly recommend using an air purifier to those of us who live in cities and suburbs in order to combat all of the gross stuff in the air around us. We also recommend purchasing one if you suffer Every. Single. Snotty. Spring Fever in agony as you (literally) blow your way through boxes of tissues. 

Can Air Purifiers Take Care of Cat Hair?

Yes, air purifiers take care of car hair, dog hai, and hare hair! They can capture stuff a lot smaller than that too, including pet dander. Air purifiers also freshen up your home’s air, cutting down on common odors that plague pet owner’s homes. Now you can have your furry family members indoors and not have to worry about what guests will smell.

What is the Best Air Purifier for Pet Fur?

The best air purifier for someone who has pets, and has an issue with said pet’s fur, will need a pre-filter. These filters will maximize the lifespan of your main filter, which ought to be a HEPA filter in order to sift allergens and odors caused by your pet. If odors are an issue with your pet, then you may need to purchase an air purifier with a carbon filter as well. 

Jonathon Silva

Jonathan Silva is our longtime Air Purifier Essentials author. He has been writing on air purification technologies for his entire professional career.

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