You can turn a standard box fan into a functional air filter by attaching a furnace filter to it. This creates a simple, DIY air cleaner often referred to as a "filter fan."
What is a DIY Filter Fan?
A DIY filter fan is an easy and affordable way to improve air quality at home. It typically consists of a box fan with a standard HVAC (heating, ventilation, and air conditioning) furnace filter attached to the back (intake) side. As the fan pulls air through the filter, airborne particles are trapped, resulting in cleaner air being blown out. According to experts, one easy and affordable way to make your own air cleaner at home is with a box fan and a furnace filter. These "filter fans" are particularly effective at filtering out small particles that are common in wildfire or wood smoke.
Why Build One?
- Cost-Effective: Much cheaper than commercial air purifiers.
- Accessible: Uses readily available materials.
- Effective for Particles: Good at capturing dust, pollen, pet dander, and smoke particles.
Materials You Will Need
Building your own filter fan requires just two main components:
- Box Fan: A standard 20-inch box fan is common and effective. Choose one with multiple speed settings.
- Furnace Filter: A 20x20x1 inch or 20x20x2 inch filter is ideal for a standard box fan. The filter's Minimum Efficiency Reporting Value (MERV) rating indicates its ability to capture particles.
- MERV 8-13: Good for general household dust, pollen, pet dander, and mold spores. MERV 13 is often recommended for better capture of finer particles like smoke.
- MERV 14-16: More efficient but can restrict airflow significantly, potentially straining the fan motor.
- Avoid HEPA filters designed for residential HVAC systems; they are too dense for a standard box fan.
| Item | Description | Recommendation |
|---|---|---|
| Box Fan | Standard square fan | 20-inch size |
| Filter(s) | HVAC furnace filter(s) | 20x20 inches, MERV 8-13 |
| Fasteners | Duct tape, bungee cords, or clamps | Secure method to attach filter to fan |
Note: Some designs use multiple filters to create a cube shape for increased surface area and airflow efficiency.
Step-by-Step Guide to Building Your Filter Fan
Here’s how to assemble your DIY air cleaner:
- Gather Materials: Get your box fan, appropriate size filter(s), and fasteners.
- Identify Airflow: Determine which side of the fan pulls air in (the intake side, usually the back with the motor visible). Furnace filters have an arrow indicating airflow direction. Ensure the arrow on the filter points towards the fan.
- Attach the Filter:
- For a single filter: Place the filter flush against the intake side of the fan. The filter should cover the entire back of the fan.
- For a multi-filter cube: Tape or clamp filters together to form a cube shape that fits snugly around the fan's intake. This increases filtration area.
- Secure the Filter(s): Use duct tape, bungee cords, or clamps to firmly attach the filter(s) to the fan. Make sure there are no gaps where air can bypass the filter. Duct tape is a common and effective method for creating a seal.
- Position and Operate: Place the filter fan in the room where you want to improve air quality. Position it away from walls or furniture that could block airflow. Turn the fan on to a medium or high setting.
How it Works and What it Filters
The fan's motor draws air through the filter material, which physically traps airborne particles like dust, pollen, pet dander, certain mold spores, and yes, the small particles found in wildfire or wood smoke. The cleaned air is then circulated back into the room.
It's important to note that this DIY air purifier is primarily effective for particulate matter. It does not effectively remove gases, odors, or volatile organic compounds (VOCs). For those pollutants, you would typically need activated carbon filters found in commercial air purifiers.
Maintenance Tips
- Check the Filter: Regularly inspect the filter. When it appears visibly dirty or airflow significantly decreases, it's time to replace it.
- Filter Life: Filter lifespan varies depending on air quality and fan usage, but they typically last from a few weeks to a couple of months.
- Fan Safety: Ensure the fan is on a stable surface and the filter does not obstruct airflow so much that it causes the motor to overheat.
Building a filter fan is a practical, budget-friendly approach to filtering airborne particles in your home.
