Cheap Air Filter – How to Enjoy Fresh, Clean Air Using a Box Fan

Creating an Air Purifier on a Budget

Cheap Air Filter DIY-Box-Fan-Home-Air-Filter

Are you on a budget and looking to have cleaner, fresher air in your home with the help of a cheap air filter?

If so, you can have an odor eliminator that is very budget friendly.

Air purifiers can be quite expensive.

It is very likely that in your search for a more cost effective way to purify the air in your home, you have seen suggestions to put a 20”x20”x1” air filter onto a box fan.

While this proves to be very effective, there is a small issue with using it this way.

Box fans are not meant to be run all of the time with a filter added to them. What happens is that the filter essentially restricts the air flow going through the fan. Over time, this puts a strain on the motor. The excess strain that is put on the motor will require more electricity to be used. This can present a fire hazard. Also, the higher the cleaning efficiency of the filter that is used, the more strain it puts on the fan.

We are going to tell you how to build a cheap air filter that is safe and easy.

It is still possible to have an air purifier that fits easily into your budget.

All you have to do is increase the filter area so that you are decreasing the overall effect of air resistance. For example, rather than using one filter that is 20x20x1, you can use two filters that are 20x25x1. This will increase the surface area of the filter. It will cost a bit more because you are using two filters rather than one, but it is still budget friendly. Having the surface area increased will also make your filter last longer before it becomes clogged.

There are many reasons that people want to purify the air in their home. These reasons can include home projects such as painting or remodeling. Using this type of air purifier will help to pull the odors out of the air, making it easier to breath. Let’s face it, many people do not want to use expensive air purifiers and filters in their home when doing dusty renovation projects because it can become quite costly very quickly.

So, let’s talk about how to make your own air purifier.


  • 2 Odor reducing air filters 20x25x1
  • 20” box fan
  • Cardboard
  • Tape (duct tape or clear tape)
  • Plug in timer (this is optional and will prevent the fan from running constantly)

Tools Needed:

  • Scissors or box cutter

About Filters:

One of the best things about using this type of air purifier setup is that you can use any type of filters that you want to. If you are mainly concerned with catching larger particles such as you would have when cutting wood, then you can use filters with much lower MERV ratings.

However, if you are more concerned with finer particles in the air such as mold or allergens, then you will want to use filters with a higher MERV rating. This is all going to depend on personal preference.

If you are looking to remove odors in the area with your air purifier, you will want to search for filters that contain activated carbon. These types of filters will help to remove the odors in the room.

Step One Open Your Filters
Credit: Tom Builds Stuff

Step One: Open Your Filters

This may seem like a silly step to describe but, it is important. Depending on how your filters are packaged, you will need to save the cardboard. If you order your filters from Amazon, they usually come well packaged in a cardboard box.

Be careful when opening your package, as you will need the cardboard as part of the project.

Credit: Tom Builds Stuff

Step Two: Hinge the Filters

Lay your filters one on top of the other with the air flow indicators pointing toward each other. Make sure your filters are lined up evenly and tape one of the short edges. This is going to create a hinge between the filters. The kind of tape that you use for this is going to be about your own personal preference. If you want a more finished look, you can match the color of your tape to the color of your filter edges.

Step Three Tape the Filters to the Fan
Credit: Tom Builds Stuff

Step Three: Tape the Filters to the Fan

During this step, you want to place the box fan face down on a flat surface. Then, you are going place the filters on the back of the fan. You want to make sure that the bottom part of your filters are even with the bottom part of the fan. Ensure that they do not go past the bottom part of the fan. When they are lined up correctly, use tape to secure them to the fan.

Step Four Attach Cardboard
Credit: Tom Builds Stuff

Step Four: Attach Cardboard

During this step, you are going to cut a piece of the cardboard. Place it over the top of filters and attach it with tape. It is not important that it is perfectly placed, just try to get it as even as possible. Use a pencil and trace around where the filters are. This is used to indicate where you need to cut the cardboard at. After you have marked the cardboard, cut along the lines that you made.

When marking your cardboard, do not forget about the feet on the bottom of the fan. You will need to allow space for them. During this step, you want to make sure that you tape everything securely so that it holds well.


Step Five Seal Everything
Credit: Marshall Hansen Design

Step Five: Seal Everything

Check the back and make sure that everything is taped well. Pay close attention to the hinged area of the filters. It is a good idea to add an additional strip of tape for good measure. Take a look all around the fan to make sure there are not any gaps, if you notice any, add tape to that area.

Replacing Filters

When it is necessary to replace your filters, simply use a utility knife to cut the filters away. When you do this, leave the cardboard in place and add the new filters.

Written by JustDIY


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