Indoor air quality is of paramount importance, especially when you consider that Americans spend the majority of their lives inside. The quality of the air you breathe at home, in classrooms, and workplaces can significantly impact your health and well-being. While high-quality air purifiers, such as HEPA devices, have gained popularity for their effectiveness in filtering out allergens, indoor pollutants, and even viruses like COVID-19, they often come with a hefty price tag.
Fortunately, there is a cost-effective solution that can provide clean air without breaking the bank. Dr. Richard Corsi, Dean of the College of Engineering at the University of California-Davis, and Jim Rosenthal, CEO of Tex-Air Filters, have collaborated to develop a simple, homemade air filtration system that costs less than a third of the price of many commercial HEPA devices.
These DIY air cleaners, known as Corsi-Rosenthal boxes, are constructed using readily available materials, including cardboard, tape, furnace filters, and a box fan. Surprisingly, early research suggests that these DIY air filters might outperform HEPA purifiers in some aspects, making them a practical and affordable solution to enhance indoor air quality, particularly in spaces with inadequate ventilation.
The Corsi-Rosenthal Box: How Does It Work?
The Corsi-Rosenthal box is ingeniously constructed using four MERV 13 air filters and a standard box fan. The box is assembled by sealing the filters with tape and affixing the fan on top. When the fan is turned on, it draws air into the box through the sides and forces it to pass through the filters, subsequently expelling cleaner air back into the room.
Initially, researchers were baffled by why the Corsi-Rosenthal box appeared to work more efficiently than high-efficiency particulate air (HEPA) filters. Despite HEPA filters being more adept at capturing particles in a single pass, the Corsi-Rosenthal box consistently outperformed HEPA filters across various particle sizes.
One theory put forth by experts is that the Corsi-Rosenthal box benefits from the exceptionally high airflow generated by the fan. This high flow rate enables the air to pass through the filters multiple times in a short period, gradually improving the overall particle capture efficiency. While it might only capture around 50% of particles during the first pass, it significantly enhances its performance with each subsequent pass.
Effectiveness of Corsi-Rosenthal Boxes
Several studies have highlighted the remarkable effectiveness of Corsi-Rosenthal boxes in improving indoor air quality. A study conducted in an academic building at Brown University found that these DIY air purifiers significantly reduced the concentration of certain chemicals, such as PFAS and phthalates, in the air. Concentrations of PFAS decreased by 40%-60%, while phthalates dropped by 30%-60% during the two-month trial period.
Another smaller-scale study compared the clean air delivery rate (CADR) of Corsi-Rosenthal boxes to that of a HEPA filter. Surprisingly, the Corsi-Rosenthal box demonstrated a notably better CADR, indicating that it could clean the air in rooms more rapidly. Additionally, the cost-effectiveness of the Corsi-Rosenthal box was evident, with a substantially lower “cost per air unit cleaned” compared to HEPA air cleaners.
The Environmental Protection Agency (EPA) advises that the best way to enhance indoor air quality is to eliminate pollutant sources and ventilate indoor spaces with outdoor air. Portable air cleaners like HEPA purifiers and Corsi-Rosenthal boxes are recommended as supplementary measures. However, it’s important to note that DIY air purifiers lack performance testing, unlike their commercial counterparts. Consequently, the EPA does not recommend Corsi-Rosenthal boxes as a long-term solution.
While indoor air cleaners can help reduce the spread of airborne viruses, they are not a substitute for measures like wearing masks and practicing social distancing in the context of COVID-19 prevention.
Building Your Corsi-Rosenthal Box
Constructing your Corsi-Rosenthal box is a straightforward process, and you can purchase all the required materials at a local hardware store. To create your DIY air purifier, you will need:
- Four MERV 13 filters.
- Duct tape.
- A 20-inch box fan.
- A cardboard box (such as the one the fan came in).
- Scissors.
The cost of the materials is typically less than $100, making this a cost-effective and accessible solution for many individuals. The step-by-step process is as follows:
1. Tape the four filters together to create the sides of the box, ensuring that the air intake direction is inward, as indicated by arrows on the filters.
2. Cut a piece of cardboard to serve as the base and securely tape it to the bottom of the box formed by the filters.
3. Position the fan on top of the filters so that it blows air outward and secure it with tape to create the top of the box. If your fan has rounded edges that do not align with the sides, you can use small wedges of cardboard and tape to fill the gaps.
4. To prevent backflow through the fan’s edges, cut more cardboard wedges and tape them to create “shrouds” for the fan’s corners. Ensure that only the circular area formed by the fan blades remains exposed.
5. Throughout the process, use ample tape to seal the edges thoroughly, ensuring that there are no air leakages.
In total, constructing a Corsi-Rosenthal box typically takes around 15 minutes.
Maintaining Your Corsi-Rosenthal Box
The longevity of your Corsi-Rosenthal box depends on several factors, primarily the environment in which it operates. Consider how often you run the device, the duration of operation, and the air quality in the area. In cleaner environments where the device runs only during the day, the filters can last for approximately 15 months. However, even when the filters appear soiled, there may still be some life left in them. It’s advisable to consult the manufacturer’s recommendations for the specific brand of filters used.
In more challenging situations, such as regions affected by wildfires, you may need to replace the filters more frequently. Replacing the filters is a straightforward process – simply cut off the old filters and attach new ones. This can typically be completed in about 10 minutes, making maintenance hassle-free.
Noise Levels of Corsi-Rosenthal Boxes
Corsi-Rosenthal boxes produce approximately 51 decibels (dBA) of noise when running, making them quieter than the average refrigerator. However, they may be slightly louder than some commercially available air purifiers, especially when the fan is set to high speed. This noise level is akin to white background noise and may be desirable in certain environments.
In conclusion, Corsi-Rosenthal boxes represent a cost-effective and innovative solution to improving indoor air quality. These DIY air purifiers, made with easily obtainable materials, offer a practical means of reducing airborne pollutants, chemicals, and particulates in indoor spaces. While they are not a replacement for established measures such as ventilation and source control, Corsi-Rosenthal boxes can serve as valuable supplementary devices for those seeking to enhance the quality of the air they breathe. By constructing your Corsi-Rosenthal box and maintaining it appropriately, you can take a proactive step towards breathing cleaner, healthier air in your home and other indoor environments.