I test several common protective face masks in a cleanroom of my own design.

This video is long because I choose to be thorough and transparent. To demonstrate this requires procedure and patience. If you are in a hurry and want to bypass all the “meat” of the video and go directly to my findings – then feel free to do so by skipping ahead to the time index of 39:17

The back story: in the early summer of 2020 I noticed many mask tests being conducted by different scientists to demonstrate the effectiveness of wearing masks to protect us from COVID-19 (and other nasty infectious diseases such as Influenza). Below is an example of one of these mask demonstrations from Dr. Rich Davis -the regional director of microbiology at Providence Health Care in Spokane, Washington.

Dr. Davis’s example along with others (listed below) inspired me to attempt a similar mask test in my classroom for my students in the attempt to show the effectiveness – and the necessity – of wearing a mask during a global pandemic.

To do this I acquired some Petri dishes (from an Amazon supplier), then – with a mask off and a petri dish held at arm’s length – I coughed, sneezed, sang, and yelled at the open dishes.  I then put on a two layer cotton face  mask and repeated the demonstration exactly as the first time. 

I labeled the dishes and let them incubate for a few days in a warm area – I did not have an incubator at the time but it was June so it was warm in the classroom, therefore – growth happened…LOTS of growth, far more than I expected…it was really gross actually and it smelled really funky. 

The odd thing was that, while the dish that was exposed to my respiratory droplets/aerosols without a mask did in fact have more colonies of growth – so did the plate I had coughed on while wearing a mask.  At first it appeared that the mask did little to stop the spread of respiratory droplets. 

I wrongly assumed my error was in the growth media of the petri dishes so I acquired some new dishes with the same growth media used by many of the other researchers – 5% sheep’s blood – and I repeated the demonstration.  This time I also added a table and placed several dishes out at 1′, 3′ and 6′ in an attempt to show how droplets travel outward from the body. 

Again, the results were the same – not much difference between masked and unmasked. 

I was perplexed. 

I compared my results to the others and came to the only possible conclusion: my samples had been contaminated by the classroom environment.  The natural dust and dirt on our feet, bodies, and hair that the students and I bring inside with us from the nearby forest and garden, our sloughed off human skin cells and hair, animal/bird dander (we have several free-range chickens), the fact that the building is an old log cabin.  Along with all this fun with particulates – the classroom is host to many different species of reptile, amphibian, fish, arachnid, and sometimes even an Opossum. Then there are the billions of free-floating fungal spores and pollen grains from the forest all around us as well as the occasional wandering house fly or gnat – and all the fun little friends that hitchhike on their feet and faces. All these contaminants and contaminant vectors were, well – everywhere.

So, my samples were contaminated by the nature of nature.

What to do? How could I reduce the natural contamination factor of my classroom environment to produce a more un-contaminated result?

A room air filter you say?  Yes, I already had one of those – a big one.  Obviously, it could only do so much.

Since it would be next to impossible to make my classroom free of natural environmental contaminants – the only option I could see was to build a Cleanroom myself in the hopes of ruling out some of the environmental contamination in the hopes of obtaining a better result – so, that is what I did.

The embedded video shows the results of my efforts and I hope it serves to demonstrate the how and the why of why masks work and why it is important to wear them during a global pandemic.

Watch to the end if you are interested in learning how I built the Cleanroom.

Special Thanks to:

Hardy Diagnostics for assisting us with this demonstration:

Beth Banks

Marian O’Neil

Jaelyn Crews Steverson

Matt Piper

My students and co-workers

More special thanks to my inspirations for this demonstration: Dr. Rich Davis, the Clinical Microbiology Lab Director at Providence Sacred Heart Medical Center in Spokane, Washington… On YouTube:…

Dr. Nwadiuto Esiobu, microbiologist, Florida Atlantic University…

Lourdes Aguilar of UMC of El Paso, TX: On YouTube:

Dr. Joe Hanson of It’s Ok To Be Smart On YouTube:

     How Well Do Masks Work:…

     COVID-19 & Mask Myths DEBUNKED!:…

My Outdoor Research Mask:…

COVID-19 Resources…………………

Even more special thanks to Matt Piper for graciously allowing the use of his wonderful song: Orbital Horizons

Please Support Matt via……

Please visit the Earthshine Nature Programs website and consider supporting our nonprofit work with a donation:

Visit our GoFundMe page:…

Support us on Patreon:


My mask protects you, your mask protects me. 

Wear your mask. 


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