Improvised filtration devices

I knew I had encountered a list of filtration efficiencies for a number of materials. The point was that in a contamination episode, you had access to any number of improvised filters that were better than nothing. I finally found a book of the handouts for my Physics 468-B class decades ago, and lo and behold!

Respiratory protection provided by common household and personal items against aerosols of 1 to 5 µ particle size

Item# of thicknessesResistance: mm H2O# of ObservationsEfficiency, Geometric mean99% confidence, lower99% confidence, upper
Handkerchief, man’s cotton16363294.292.6395.5
Toilet paper3133291.489.892.8
Handkerchief, man’s cotton8183288.985.591.6
Handkerchief, man’s cottoncrumpled3288.185.190.5
Bath towel, Turkish2113285.183.386.8
Bath towel, Turkish153073.970.778.8
Bed sheet, muslin122327268.874.9
Bath towel, Turkish1 (wet)33170.26872.3
Shirt, cotton1 (wet)>150 (a)1565.957.972.3
Shirt, cotton273065.560.869.6
Handkerchief, woman’s cotton4 (wet)84 (a)326357.358.7
Handkerchief, man’s cotton1 (wet)98 (a)3062.65767.5
Dress material, cotton1 (wet)180 (a)3156.349.662
Handkerchief, woman’s cotton4 (wet)23255.552.258.7
Slip, rayon16325046.253.6
Dress material, cotton153147.641.453.2
Shirt, cotton133234.62939.9
Handkerchief, man’s cotton123227.52232.5

(a) Resistance obtained when checked immediately after hand wringing. This resistance began to decrease after about one minute when the material started to dry.

I’m not sure of the original source. It may be an old version of an OSSHA handbook.

How to Develop the Situational Awareness of Jason Bourne | The Art of Manliness

Source: How to Develop the Situational Awareness of Jason Bourne | The Art of Manliness

Further Reading and Resources on Situational Awareness

Podcast: Situation Awareness With Patrick Van Horne: We talked with Patrick Van Horne about how situational awareness skills can be used beyond the battlefield.

Left of Bang by Patrick Van Horne and Jason A. Riley. Patrick has spent his career researching and teaching situational awareness to Marines through the Marine Combat Profiling system that he helped create. This book, coupled with the articles at his site and a personal interview with him went a long way in helping answer my questions. This is Patrick’s company website. He has tons of free content that provides insanely useful information on developing your situational awareness. If you’re looking for something more structured, he also offers online courses.

“Toward a Theory of Situation Awareness” by Dr. Mica Endsley. Dr. Mica Endsley is the Chief Scientist at the U.S. Air Force. While Dr. Endsley’s paper is pretty technical, she does a fantastic job explaining the minutia and nuances of situational awareness that helped clarify a few things for me. I highly recommend you check it out.

Streetlights and Shadows: Searching for the Keys to Adaptive Decision Making by Gary Klein

The Gift of Fear by Gavin de Becker