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Air Filtration Trends that Don’t Work

By March 18, 2022 March 21st, 2022 No Comments
22–27 minutes to read

The COVID-19 pandemic has highlighted the importance of breathing clean air, leading many people both in the United States and across the world to consider air quality for the first time, due to airborne transmission of the disease. In 2021, schools, offices, and other public spaces worked to make it possible for Americans to return to normal activities, while individuals worked to make their homes a safe place for visitors.

As indoor air quality became a prominent public health concern and organizations such as the WHO, the EPA, and the CDC recommended ventilation and air filtration to reduce the spread of the virus, some manufacturers took the opportunity to push products that supposedly combatted the virus. Some of these technologies provide a false sense of security by allowing consumers to think that they are safe when the risk of infection is still high, while other technologies compound air quality issues by releasing ozone, volatile organic compounds (VOCs), and other dangerous chemicals into the air. 

In this article, air filtration experts and engineers from Camfil — a global leader in air filtration technology — highlight  the dangers of some of 2021’s most unreliable air quality trends. 

Using  consumer-grade MERV-13 filters sourced through retail outlets instead of MERV-A-rated filters

Throughout 2020 and 2021, you probably heard the term “MERV-13” used a lot in the news, by government bodies, and by agencies such as the CDC. In some areas, there were mandates that required public buildings such as malls to install MERV-13 filters in the HVAC systems before reopening to the public. 

Although you may be able to easily find MERV-13 filters at your local big box retailer for a low price point, these inexpensive MERV-13 filters don’t maintain their rated efficiency for long, and therefore need to be replaced frequently to provide adequate protection against COVID-19. This is because they rely on an electrostatic charge to increase particle capture efficiency. Once this charge dissipates, which can happen in as little as a month, the filter no longer operates at its rated efficiency. In fact, once MERV-13 filters lose their electrostatic charge, they operate at a particle capture efficiency equivalent to that of a MERV-9 or even a MERV-8 filter.  

Many HVAC systems in commercial buildings only have the capacity for filters that are one,  two, or four inches deep. MERV-13A filters utilize filter media produced with far more fine fibers in those same depths which could increase the pressure drop higher than what the HVAC system is designed to handle. Six- and twelve-inch deep MERV-13A filters can have pressure drops compatible with the HVAC system, but may be physically too large to fit in the unit.

However, if you are unable to replace your HVAC unit to accommodate the depth of a MERV-13A filter with similar pressure drops, and if you are unwilling to incur the added expense of frequent filter changeouts when standard two-inch deep MERV-13 pleats lose efficiency, one strategy to consider is to choose a filter with a MERV-A value lower than MERV 13 such as MERV 8A or 9A. This is because when filter performance drops below  rated efficiency, they lose effectiveness and stop protecting building inhabitants by letting more dirty, contaminated air into the space.This higher dirt load also places a strain on HVAC equipment, which can lead to costly repairs. 

Read about the difference between MERV and MERV-A ratings: What Are MERV Ratings? MERV vs MERV-A Filter Efficiency Ratings Explained   

DIY box filter “air purifiers”

Leading up to the beginning of the academic year, recipes for “DIY air purifiers” using box fans and inexpensive panel filters swept across the internet. Teachers and parents across the country saw this as an inexpensive way to protect their children from contracting the virus at school. One argument proponents of these DIY air purifiers made was the box fan’s high circulation rate meant that the room it was operating in would get more air changes per hour than a high-end HEPA air purifier. 

While this is technically true, more ventilation isn’t necessarily better, because pushing air through ineffective filters over and over again doesn’t mean that the air gets as clean as imagined.  As mentioned above, the consumer-grade MERV-13 filters that you can easily buy on Amazon or from a local big box retailer degrade quickly leaving you unprotected in as little as a month of regular use in an HVAC system.   

“The single biggest objection I have to the claims around these boxes ,” comments Steve Smith, CamCleaner Segment Manager at Camfil USA, “is the MERV 13 pleated filters do not have the particle capture efficiency required to remove a significant amount of potentially virus-laden aerosols from the air stream in a single pass. Expecting this device to be as efficient as a HEPA filter could lead to a false sense of security and actually increase risk.”

While these DIY air purifiers are a creative solution to certain air quality concerns — such as removing pet fur from the air in your home or preventing the buildup of sawdust in your home workshop — they are not an appropriate solution for protection against COVID-19. 

Read Camfil’s full article on the effectiveness of DIY air purifiers: Do “DIY Air Purifiers” Work Against COVID-19 In Schools? Not Exactly, According To Air Filtration Experts

Using cheap “HEPA” air purifiers that lack actual HEPA filters

An effective in-room air purifier with HEPA filters is an excellent way to protect yourself against a wide range of air pollutants, including COVID-19 infected aerosols, allergens such as pet dander, dust,  pollen, and other particulate matter. 

However, due to increased demand for effective HEPA air purification systems, and millions in federal funds,  dozens of new products have appeared on the market to capitalize on public concerns about air quality and infection. The use of the term “HEPA” is somewhat unregulated, meaning that manufacturers  could falsely claim that their products use HEPA filtration. 

HEPA filter stands for high-efficiency particulate  air filter. An actual HEPA filter will be individually factory tested and come with paperwork showing the results of these tests. A scan tested and certified H14 HEPA filter (as found in the Camfil City M) is 99.995% efficient on MPPS-sized particles on a single pass. In other words, when air passes through a HEPA filter just once, a minimum 99.995% of the particles most difficult to capture, (MPPS stands for most penetrating particle size and is typically between 0.1 and 0.2 microns) are removed. 

If you are considering purchasing a HEPA air purifier, be certain to choose one from a well-regarded air filtration manufacturer, and make sure that you can access the factory testing and HEPA certification paperwork. If the only place you can find the word “HEPA” is on the outside of the box, that’s a red flag. Also, if it sounds like it’s too good to be true for its price, it probably is. 

For additional protection against harmful indoor air pollutants, choose an air purifier that uses an activated carbon filter, or other molecular filter that effectively targets gaseous pollutants such as ozone, carbon monoxide, and nitrogen oxides, in addition to HEPA filters. 

Related article: What The Heck Are HEPA Filters – And Why Should You Care?

Using antiviral or antimicrobial filters

Another unnecessary and potentially harmful air filtration trend that took off in 2021 is the use of antibacterial or antimicrobial filters. Air filter manufacturers are offering filtration products that are treated with biocides and other chemicals that are supposed to kill bacteria, viruses, and other pathogens in the air. 

On the surface, this solution might seem reasonable. However, as is the case with ionizers, antimicrobial filters are potentially ineffective, definitely unnecessary, and may cause more harm than they prevent. 

Firstly, many experts in areas such as air filtration and infectious diseases have pointed out questionable science behind the claims these products make. Most of the testing applications that point to the supposed effectiveness of antimicrobial filters against COVID-19 are not relevant to real-life applications or even applicable to air filtration purposes, with many tests using filters submerged in liquid. After conducting research on the effectiveness of antimicrobial filters by applying three different EPA registered treatments to filters, ASHRAE (the American Society of Heating, Refrigeration, and Air-Conditioning Engineers) concluded that “the addition of antimicrobial [coating] on filter fibers had little effect on the growth (or lack thereof) of microbial contaminants on the filter.” Other studies have shown that while some chemical treatments may work to kill pathogens at first, they steadily decrease in effectiveness over time. 

Secondly, antimicrobial treatments for air filters are unnecessary if the filters being used are effective enough to capture infected particles. High efficiency air filters, such as MERV-A rated HVAC filters and HEPA filters, are made of dense filter media configured to capture as much particulate matter as possible. Once infected virus particles are captured by these filters, they are trapped, and cannot escape to infect people. Though the SARS-CoV-2 virus  may be able to survive longer on surfaces outside of the human than originally thought, they will eventually dry out and  die while trapped in a regular filter. 

Finally, the chemicals used in antimicrobial and antiviral filters can be dangerous to humans. Unlike the kinds of antibiotic and antiviral medications that we ingest when we are sick, the chemicals used in these filters are not safe for human consumption, and can be dangerous for us to inhale. When antimicrobial filters are placed in HVAC systems, these chemicals are constantly pushed around the air stream, causing potential harm to building inhabitants. 

It is unpleasant to breathe in the residue left behind after a surface is cleaned with bleach or another heavy-duty disinfectant, and the buildup of these chemicals in the air can cause respiratory irritation, dizziness, and headaches. The long and short-term effects of antimicrobial filters aren’t entirely known, but may cause similar health risks.

Read more on antiviral and antibacterial filters in this article from our colleagues at Camfil Canada: An Analysis of Antiviral/Antimicrobial Filters and Impacts on Indoor Air Quality. 

Using air purifiers with photocatalytic oxidation

Photocatalytic oxidation is a process that involves ultraviolet light and a chemical catalyst to change harmful particles in the air into relatively benign substances (water, carbon dioxide, and detritus). The most common catalyst in air cleaners that use photocatalytic oxidation (PCO) is titanium dioxide (TiO2). While some manufacturers of air cleaners have implemented photocatalytic oxidation as a means of supposedly enhancing protection against COVID-19, organizations including ASHRAE recommend caution when using such devices. 

Firstly, air cleaners and air purifiers that use photocatalytic oxidation can produce small amounts of ozone. Secondly, volatile organic compounds (VOCs), which are commonly found in indoor air, a photocatalytic air purifier may convert them to other unpleasant pollutants, such as formaldehyde and acetaldehyde. It is overall more beneficial to remove these pollutants from the air entirely than to attempt to convert them to other substances. 

Another issue to consider with photocatalytic air purifiers is additional power consumption is required to operate the multiple components within the system. Potentially compounding that issue is the more components a system requires, the higher the likelihood one component will fail which could lead to costly repairs and downtime.  

Air filtration products with dry hydrogen peroxide

Dry hydrogen peroxide (DHP) is a gaseous form of hydrogen peroxide, a powerful disinfectant and antiseptic. “Dry” indicates that it is not a vaporized form of liquid hydrogen peroxide — instead, it is formed using chemical reactions between gases in the air — so it doesn’t have the same corrosive properties or weak acidic pH as liquid hydrogen peroxide. Some  new HVAC technologies  use dry hydrogen peroxide, claiming that it will essentially disinfect the air. 

Several studies have shown that dry hydrogen peroxide is highly effective against SARS-CoV-2 on surfaces, but there is little evidence to suggest that it has any significant effect against the virus when it is airborne. 

Furthermore, dry hydrogen peroxide interacts with other chemicals in the air in a potentially dangerous manner, according to the Socioeconomic Data and Applications Center (SEDAC).  While the concentrations of DHP generated by air purifiers using this technology are not dangerous on their own, the EPA cites the partial reaction between DHP and VOCs in the air as one of the primary concerns when it comes to using DHP for disinfection. These chemical reactions produce harmful byproducts, including nitrogen dioxide, formaldehyde, and carbon monoxide. 

Low wattage UV light with limited exposure time

At the right frequencies, UV (ultraviolet) light kills certain pathogens. UVC light, which has a frequency of 200 to 280 nm (nanometers), has been shown to destroy the outer protein coating of the SARS-CoV-2 virus, essentially inactivating the virus. 

UVC light, however, is more harmful than other frequencies of UV light, with higher risk of more severe side effects. While UVC light is effective for killing viruses in the air and on surfaces, it should not be used while people are in the room. 

UV light is also being used inside of air purifiers. The idea behind UV air purifiers is that they sterilize the air as it passes through. However, air moves through an air purifier at a high velocity, which means that the period of time it is exposed to UV light frequencies is very brief. To compensate for short exposure time, a bulb with a very high intensity would be required, which increases cost and magnifies health side effects associated with UVC light. 

The FDA recommends careful use of UV light as a supplement to adequate air filtration and ventilation, not a replacement. 

When viewing new air filtration products, consider the evolution of technology, the search for a better mousetrap, has taken us from the wheel to internal combustion powered automobiles to rockets and to where we are today; a helicopter flying remotely over the surface of Mars.  At this point in the evolution of air filtration technology, a high quality air filter produced with fine fiber media utilizing the principles of mechanical air filtration, delivers the highest performance. Some of these new technologies are a step backwards. While others have value, they should all be considered supplementary to mechanical air filtration. 

About Camfil Clean Air Solutions

For more than half a century, Camfil has been helping people breathe cleaner air. As a leading manufacturer of premium clean air solutions, we provide commercial and industrial systems for air filtration and air pollution control that improve worker and equipment productivity, minimize energy use, and benefit human health and the environment. We firmly believe that the best solutions for our customers are the best solutions for our planet, too. That’s why every step of the way – from design to delivery and across the product life cycle – we consider the impact of what we do on people and on the world around us. Through a fresh approach to problem-solving, innovative design, precise process control, and a strong customer focus we aim to conserve more, use less and find better ways – so we can all breathe easier.


The Camfil Group is headquartered in Stockholm, Sweden, and has 31​ manufacturing sites, six R&D centers, local sales offices in 30 countries, and about 5,20​0 employees and growing. We proudly serve and support customers in a wide variety of industries and in communities across the world. To discover how Camfil USA can help you to protect people, processes and the environment, visit us at 




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Camfil USA Air Filters 

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