DIY Air Purifiers to Improve IAQ
Cesar Collado
January 18, 2023
DIY Air purifiers Hero

Is Indoor Air Quality Essential? Can DIY Air Purifiers Help?

The Corsi Rosenthal Box became a viral sensation on social media for people to contribute DIY Air Purifiers to schools, churches, and other large indoor meeting places curing the pandemic.   Clean air is the single most important contributor to health that has not seriously taken into consideration by us nor our physicians.  As a result of the pandemic, IAQ awareness has improved.  Furthermore, clean air is critical to health because it helps to protect against a variety of respiratory and other health problems.

When Indoor Air Quality (IAQ) is contaminated with pollutants, it can cause or exacerbate health issues such as asthma, allergies, and other respiratory conditions. In addition, exposure to certain chemical pollutants has been linked to an increased risk of heart disease, stroke, and other serious chronic illnesses.  As a result, poor air quality with mold contamination can also impact the immune system, making people more vulnerable to infections, disease, and other health problems. It can also be the underlying cause of fatigue, headaches, and other symptoms that can impact quality of life.

Mold Problems

Mold contamination due to excess moisture can also have a significant impact on occupant health due to a genetic predisposition. As a consequence, mold exposure may impact one person in a home without impacting others. Visual mold or a musty smell is practically a no-brainer when it comes to determining whether you have a mold problem.

The most important next step is to find the source of the water or moisture problem and repair it. Inevitably, you will find damp or discolored building materials or visual mold. A DIY air purifier is not a sole solution to address issues.  In combination with removing the mold source, It will help filter large particulates from air and contribute to improved air exchanges.

There are a variety of tests you can perform to qualify the presence of allergenic or toxic mold. Often mold inspectors with special equipment are required to quantify the mold problem. Overall, it is not practical or necessary to try to quantify the number of mold spores. Instead, the focus should be on preventing amplified mold growth by addressing any moisture issues and removing existing mold problems in a home.

You can be assured that if you can see it or smell mold or musty smells, it is a significant problem. Single mold spores are microscopic and unseeable to the naked eye. To illustrate, approximately 250,000 spores can fit on a pin head. As a result, a person can easily inhale as many as 750,000 of these airborne spores per minute.

Mold inspectors use a variety of precise testing methods to determine the type and severity of mold present in your home. Testing methodologies include DNA testing multiple samples as well as lab microscopy.

DIY Testing

Perhaps the easiest and least expensive method is DIY mold testing. If you suspect mold, ImmunoLytics Mold Test Kits provide a very comprehensive and easy-to-understand tool for the DIYer. Homeowners can verify mold existence through visual results or obtain a detailed lab report identifying mold species and potential dangers. You can simply follow directions to send mold test plates or swabs to the lab for testing.

DIY air purifiers. Immunolytics test kits

Clean Air Heals

Alternatively, breathing clean air can help to improve overall health and promote healing. It can help to reduce the risk of respiratory and other health problems. Toxic mold exposure can be the cause of severe symptoms like those created by serious chronic illnesses. These symptoms mimic other chronic illnesses and misdiagnosis is not uncommon.

Air Purification

If you are experiencing severe chronic symptoms, I believe that an important step in improving the quality of your air at home is to add air purification where you spend your time and sleep. You can purchase a commercial air purifier or make your own DIY air purifier.

While this does not solve the mold or pollutant source problem, it will help to answer the simple binary question on whether clean or purified air makes you feel better. A carefully placed air purifier will help address your immediate air. It is important to note that HEPA air filters remove 99.7 pf particles down to .3 microns (µm). There are many gas particles and microorganism (such as viruses) that are considerably smaller that can get through the filter. The filter are effective in collecting many these smaller particles when present in airborne respiratory droplets; however, there is no guarantee they will remove them all.


Size in µm

Mold Spores 2-5
Bacteria 0.3-10
Viruses 0.02-0.3
Hepatitis B 0.045
Adenovirus 0.08
Influenza 0.08-0.12
Coronavirus including SARS-CoV-2 0.125
Droplet nuclei from sneeze/cough 0.125-20
Droplet nuclei from influenza room <1-4
Water molecule 0.0003
Hydrogen sulfide 300 pm/0.3 nm
Carbon dioxide 0.00036
Smoke particles 3.6 A/360 pm/0.36 nm
Denatonium- quaternary ammonium cation (Bitrex) (MW) 0.0025-1.0 2.5-1.000 nm

About Commercial and DIY Air Purifiers

Air purifiers come in a variety of sizes and prices. There are several types of air purifiers that can be purchased and placed is specific areas of your home to help improve your immediate air source for healthier living or healing.

Not Recommended:

Charcoal Air Purifiers:

These air purifiers utilize charcoal to absorb gasses and other chemical compounds in the air. Charcoal purifiers are often used to eliminate odors in specific areas. Although helpful, they do not do enough by themselves to improve overall air quality. However, they are perfectly acceptable to be used in conjunction with HEPA filtration.

UVC Air Purifiers:

These products filter the air through an ultraviolet light that is supposed to kill bacteria and other microbes. As with Charcoal Air Purifiers, they are typically fine to use, but should be paired with other air purification techniques. One point of caution, ensure that ozone is not being produced by the UVC Air Purifier. Ozone is easily detected by its odor.

“New Patented” Technology Air Purifiers:

These air purifiers have entered the market at both low- and high-priced segments. Current reviews suggest limited efficacy when compared to HEPA filter air Purifiers. Many come with novel “Ionic” or “Ozone” descriptions. Ozone technology has merit but also brings potential harmful elements to the consumer. Ozone is best used only by professionals in unoccupied environments.

Do Not Mistake the Following for an Air Purifier!


These appliances add humidity to the air. These are often problematic as the filters effectively combine dust and moisture to become extremely moldy. The fan then redistributes mold into the air. If using a humidifier, it should be inspected and cleaned every couple of days to prevent the growth of biologic material, which would then be dispersed by the humidifier fan.


Dehumidifiers are excellent additions to HVAC system, crawlspaces, and inside homes. The appliance may have a filter to be rinsed on occasion; however, these are by no means adequate to filter air of microparticles.

Essential Oils or Aromatic Diffusers:

Like all chemical fragrances, adding odors into the air in order to mask other smells simply adds VOCs to the pollutant count being inhaled. Chemically sensitive individuals may have symptoms when exposed. However, if tolerated, several essential oils do have antimicrobial properties that make them suitable for treating mold and bacteria contaminated environments.

DIY Air Purifiers: Recommendations

True HEPA Air Purifiers: These air purifiers contain High Efficiency Particulate Air (“HEPA”) filters. These high quality, multilayer, pleated filters will remove 99.97% of particulates 0.3 µm and larger.

Consumer Quality HEPA Filters:

These HEPA filters are effective in maintaining air quality in multiple room sizes and include brands like Honeywell, Filtrete, Shark, PureAir, and many others. A large unit that will serve up to 1000 sq. ft. can cost anywhere from $150-350 at a Walmart, Home Depot, or Costco. You can expect these brands to have a 1-year warrantee and last 1-3 years.

Commercial Quality Air Purifiers

These units are built to be used 24/7. They are quieter and will last up to 5 years or more. Brands like IQ AIR, Austin Air, Blue Air, other European and Asian brands. The costs can range from $600-$1000 or more. They also have warranties up to 10 years.

Corsi-Rosenthal Box -DIY Air Purifiers

Finally, there are solutions for those who want to experiment with the idea that the air in their homes can help them feel better. There are low-cost alternative that carry no guarantees; however, these DIY units have been tested and have impressive performances, although less effective than a portion of the purchased purifiers.

The most notable of DIY air purifier was created in 2020 by researcher (Dr. Richard Corsi) and the CEO of an air filter company (Jim Rosenthal). The two men creatively combined efforts to develop an extremely effective and inexpensive air cleaner.  This open-source design uses 4 filters and a cardboard bottom to eliminate the pressure and stress of a single filter DIY unit and has been used extensively in schools, churches, homes, and office buildings to remove particles like dust and smoke from wildfires. The cost to build a Corsi-Rosenthal Air Purifier is estimated at less than $100.

DIY Air Purifier Materials:

  • A box fan (20”x 20” is preferable) Cost est. $20-30
  • Four furnace or heat pump filters (20” x 20”) are easy to find (MERV (10-12) Cost est. $12-20 each
  • Roll of Duct Tape or Clear Boxing Tape. Cost: $5

DIY air purifiers. Corsi-rosenthal Box instructions

Rosenthal, J (2020, November 4) How to Improve the Efficiency of the Corsi-Rosenthal Box Air Cleaner

Rosenthal, J (2020, August 22) A Variation on the “Box Fan with MERV 13 Filter” Air Cleaner

Twitter: @corsiIAQ, @jimrosenthal4, @kprather88


This Corsi/Rosenthal DIY air purifier may not be as effective as some commercial air purifier; however it outperformed many. It can clearly improve the air quality in a room. You may need to replace the air filter every 3-6 month or so, depending on the level of pollution in your home and the size of the filter. Discoloration will indicate the need to replace.

This open-source design uses 4 filters and a cardboard bottom to eliminate the pressure and stress on the fan motor when a single filter attached to a fan. Thee use of these boxes went viral in 2020 and have been used extensively by communities in schools, churches, homes, and office buildings to remove particles like SARS-Cov-2 and smoke from wildfires. Cost est. <$100. These filters must be replaced every 3-6 months or when they are visually dirty. It must be noted that airborn viruses are significantly smaller than the .3 microns; however, respiratory droplets that contain the viruses will be captured by the filters. In summary, the filters will not remove all viruses; bit the area will benefit from the air exchange.

DIY air purifiers. Corsi-Rosenthal Box

These purifiers have been tested side by side with other commercial and residential grade air purifiers. These DIY air purifiers outperformed several commercial brands; but quality commercial air purifiers are the most efficient. It is important to note that Corsi-Rosenthal Air Purification Boxes are cost effective on a cost/ cu. ft. of air filtered. It can cost as little as 1/10th the price of high quality air purifiers. You can also make a DIY air purifier with 1, 3, 4, or 5 filters with the same materials. Simply use the box that the fan comes in to fill in the blanks.