Coronavirus Technology Solutions

September 10, 2020

Filters and HVAC Choices to Mitigate COVID-Webinar Overview

Filters and HVAC Choices to Mitigate COVID-Webinar Details

Freudenberg Air Filter System Used by Ford

Can Purdue Photosensitizer be Used in Vehicles as Well as Classrooms?

More Efficient Filters are Worth the Cost


Filters and HVAC Choices to Mitigate COVID-Webinar Overview

This 90 minute webinar covered ways to filter the air in buildings and vehicles using the most cost effective products and technologies. The benefits include protection from air pollutants as well as viruses.  Christine Sun of Waterloo Filtration Institute outlined the potential benefits. Bob McIlvaine provided evidence that most COVID transmission is through small aerosols. Some of these aerosols are generated when larger droplets are only temporarily captured by inefficient masks and filters.

Bob Burkhead of Blue Heaven Technologies then described the testing rig which could be adapted to test filter efficiency over time and not just measure what is temporarily captured.  This rig allows recirculation of up to 1000 cfm and can measure degradation of meltblown media over time, ozone levels when ionizers are utilized, and other contaminants which need to be assessed over time.

Barry Kellar, Saru Dawar, and Uwe Haffner of Freudenberg talked about the needs in vehicles where conditions are rapidly changing. The company is addressing the potential for aerosols generated from surfaces as well as directly from people and has an efficient filtration system which includes a surface layer of a proprietary citric acid compound which inactivates the virus.

Freudenberg recognizes the role of very fine particles (smaller than 0.3 microns) and is looking at capture rates on activated carbon due to diffusion. There was a brief discussion on the potential to spray citric acid in vehicle interiors similar to the Purdue concept of spraying food dyes into classrooms. Bob McIlvaine then summarized market aspects such as the much higher efficiency of H13 filters than MERV 16 in capturing small particles and virus. The decision on which product to choose is enhanced by a value system which takes into account lives saved and sickness reduced compared to the economic and life quality costs.

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Filters and HVAC Choices to Mitigate COVID-Webinar Details

Indoor air quality is important for many reasons in addition to COVID. WFI just held a webinar on the subject  which can be viewed at  Open Educational Webinar  


Bob  Burkhead described the testing rig  which is used to test filter efficiency over time.  It is has the capability to treat 1000 cfm.  It also has a conditioning loop to control temperature and humidity.


The unit has lots of uses. One could be the testing of filters to capture virus over time.  If large droplets are continuously sprayed into the system there would likely be an initial higher efficiency than later when droplets are evaporating and generating aerosols.

Freudenberg Air Filter System Used by Ford

The Ford micronAir proTect filter, developed by Freudenberg’s experts, is highly effective in capturing a wide range of harmful germs, allergens and even viruses, which can cause significant health problems.

The advanced system uses carbon combined with a special active layer obtained from a secret recipe that includes citric acid, present in lemons. This system provides protection against unwanted bacteria, yeasts and fungi, while also offering antiviral properties.

“For many drivers and their passengers, allergies to pollen and dust can cause great discomfort, as well as serious health problems,” said Nigel Brackenbury, Vice President, Ford Customer Service Division, Ford of Europe. “This filter is an economical but effective measure that could protect health and offer greater comfort to anyone traveling in a Ford vehicle.”

The Ford micronAir proTect is capable of trapping very small particles down to 0.05 microns – less than a thousandth the thickness of a human hair. If mounted on the vehicle’s ventilation system, it can dilute the concentration of harmful particles entering the cabin and remove droplets containing viruses as quickly as possible, reducing the possibility of further contamination and infection.

The filter features an activated carbon element designed to offer additional protection against harmful pollution, such as particles and acid gases, and a multilayer microfiber barrier that retains the smallest particles, dust and pollen.

In addition, the filter acts actively against some agents that are located in the passenger compartment, demonstrating a 99.9% effectiveness in inactivating the viruses that come into contact with the special active layer. These include swine flu (H1N1) and the HCov-229E virus. Current conditions make it too dangerous to test the filter against SARS-CoV-2, the coronavirus that causes COVID-19-related disease, but Freudenberg estimates 99.9% effectiveness in this case too.

Coronaviruses spread in droplets produced when affected people sneeze, cough or breathe and can remain contagious on surfaces for hours or even days. Wind, changes in temperature and humidity can put these particles back into circulation, which, at that point, can be picked up by the filter.

The Ford micronAir® proTect filter has an anti-viral surface protection developed through the use of a functional filter layer based on fruit extract (active ingredient citric acid CAS-Nr. 77-92-9 and / or 5949- 29-1) for use in air treatment/conditioning systems. Safe bacteriostatic and fungistatic surface protection against a multitude of gram-positive and gram-negative bacteria, yeasts and fungi, as well as proven antiviral properties (Influenzavirus H1N1 and Coronavirus HCoV 229E) according to ISO 18184.

Can Purdue Photosensitizer be Used in Vehicles as Well as Classrooms?

This point was briefly discussed  with Barry Kellar, Uwe Haffner, and Saru Dawar of Freudenberg. There would seem to be potential for decontaminating a vehicle in the same manner as a classroom

Photodynamic therapy uses a photosensitizer, a chemical that reacts with oxygen in the presence of light, to produce oxygen free radicals. These radicals are highly reactive, meaning they trigger other chemical reactions, including ones that kill harmful pathogens.

Instead of using expensive medical photosensitizers, Purdue has identified several FDA-approved food coloring dyes that can be used to generate free radicals in visible light. The system uses ultrasound to generate small aerosols containing the food coloring so that the dyes can float and linger in the air. The aerosols are barely visible, and their small size and short lifespan in light means they don’t stain surfaces.


A humidifier-like device dispensing mist in a classroom


More Efficient Filters are Worth the Cost

This was the webinar conclusion based on using a value rating system.






This net value ranking is completely at odds with what has been advised by CDC and WHO.  However, it is consistent with the ranking to fight air pollution or measles. In both cases the assumption is that if there is a source it will be airborne for long distances.

There are some who argue that there is not sufficient proof that the virus will remain viable after being airborne. There has been lots of indirect evidence where other causes were eliminated. Now we are seeing direct evidence where with new sampling methods which do not damage the virus there are viable specimens being captured.

There are some who argue that the small amount of virus conveyed by small droplets is not going to be infectious. New evidence shows that the quantity of virus in small droplets emanating directly from lungs is much higher than in cough droplets which are composed of mucus with diluted virus quantities.

The fact that surfactants make up about 4% of large droplets means that as these droplets evaporate on the mask or filter surface the surfactant concentration will increase and the surface tension be reduced to make the formation of smaller droplets easier.