People who’ve operated a vehicle powered by an internal combustion engine are probably at least somewhat familiar with an air filter, if for no other reason than it is periodically replaced in standard maintenance. Air filters are also essential components in heating and cooling, electronic, and mass transportation systems, to name a few. Clean particle-free air is crucial for such mechanical systems to function as designed.
Owing to their inherent proximity to a palette of toxic compounds, liquids, and gasses, elite high-power rocketeers are well-versed in the critical importance of air filters in protecting one’s personal physical well-being.
- When sanding wooden components of rockets, such as plywood bulkheads or fins, we use a “N95” US-made respirator which successfully filters 95% of airborne particles which are three microns or larger in size. The designation “KN95” indicates a N95 respirator manufactured in China.
- When sanding fiberglass, carbon fiber or polyparaphenylene terephthalamide (trade name Kevlar) components we use an “N99” respirator—which successfully filters 99% of airborne particles three microns or larger in size.
- When using materials and methods which emit harmful gases, such as when making solid propellant, degreasing components, or using automotive paint, we use a full-face gas mask with two activated-carbon filters.
Mechanically, the COVID-19 pandemic exists because harmful airborne microbes enter and infect human bodies when people take a breath of air by mouth or nose.
From a public health perspective it is thus crucial that all people understand:
- A face mask (FM) is an air filter.
- The function of a FM is to prevent or limit the exchange of unfiltered exhaled air between people.
- The objective of a FM is to safeguard human health and help end the pandemic.
Properly worn, personal air filters reduce the chance of acquiring from others, and/or transmitting to others, COVID-19 and other pathogenic airborne microbes.
Here are two articles reporting that FM mandates can and do rapidly reduce the number of new COVID-19 cases and deaths.
There two ways to wear a FM: correctly or incorrectly.
Failing to wear a FM, or wearing a FM incorrectly, increases the likelihood that one’s exposure to an airborne pathogen will have negative health consequences.
- Worn correctly the FM fits snugly over the nose and mouth, and little or no unfiltered exchange of breathed air, or of air exhaled by others occurs.
- If a FM fits poorly—for example, fails to cover one’s nostrils, or leaves gaps anywhere due to a loose or misaligned fit, then protection is compromised.
I personally use two types of FMs.
My favorite type of FM has an elastic strap which fits behind my head on my neck, and another elastic strap that fits on the crown of my head. This type of FM is easy to adjust so that it fits comfortably and snugly on my face.
- If I have a dangerous appointment, such as a meeting at a medical center, I wear a N95 or KN95 FM with straps.
- If I had unlimited funds, I’d wear a single-use N99 strap FM on every occasion. As dear Aunt Irka was fond of saying, “better safe than sorry.”
In more benign situations I wear a more economical four-ply, two-ear-loop FM: one loop “fits” behind each ear. Loops are constructed of an elasticized cord which stretches less than strap, and is attached to the FM less securely than is strap.
Instructions for many ear-loop FMs state: “One size fits most.” I use four-ply ear-loop FMs of various brands, none of which fit me perfectly.
- Sometimes the ear loops are too short—thus invalidating their use.
- Sometimes the ear loops are too long, ceaselessly exposing one’s nose and/or mouth, and requiring reorientation via hand manipulation—thereby potentially exacerbating the spread of pathogenic microbes.
Accordingly, described below, I created a reliable, simple, inexpensive, reusable method requiring only three rubber bands, which makes every ear-loop FM that I’ve yet tried fit me perfectly.
Here is a photo of the “raw” materials used in this demonstration: one ear-loop face mask, and one 2” and two 3.5” rubber bands (1/16” or 1/8” wide bands are best).
After washing one’s hands the first step is folding the FM in half, and keeping all materials on a clean surface, as seen in the following photo.
Next, overlay the two long rubber bands as illustrated in the following photo.
Next, thread the part of the right-hand rubber band which is underneath the left-hand rubber band over the right-hand-edge of the left-hand rubber band, and then under the right-hand-edge of the right-hand rubber band, as seen in the next photo.
Pulling on the ends of both rubber bands, cinch the knot tight as seen below.
Pick up the FM by the ear loops, and then pass the cinched rubber bands (seen above) through the ear loops, with the cinch knot in the middle, as seen in the next photo.
Next, pass the 2” rubber band beneath the two longer rubber bands, as seen below.
Pull the left end of the 2” rubber band over the top of both of the longer rubber bands, and then through the right end of the 2” rubber band, as seen in the following photo.
Cinch the 2” rubber band just tight enough to close the knot. The knot won’t slip, and it makes it easier to disassemble this “choke” (as it was called by an elevator electrician who saw this rig) so it may be used again when needed.
Put the FM on before putting anything else on or into your hair: then pull the FM down beneath your chin, finish preparing yourself, and pull the mask up before opening the door to go outside.
The type and quantity of adhesive used to attach ear loops to the face-covering-component of the FM is generally weak (I’ve checked customer reports for many brands on Amazon Prime). Ear loops thus dislodge easily if they are pulled—ruining the FM.
However, using the rig described in this post, one can avoid detaching the ear loops by firmly holding the right- and left-hand ear loops, and stretching the rubber bands without applying pressure to the ear loop connections to the face covering component.
There is a bit of a learning curve for this rig. I still accidentally tear ear loop cords off the body of the FM—mostly when I forget my headband is on. When my headband is off and I pay attention to what I’m doing, I rarely ruin a FM by dislodging an ear loop cord.
After trying a handful of methods, I stopped after discovering the three-band-choke system described in this post. It’s not perfect, but it is simple, cheap, fast, and it reliably keeps the FM over my nose and mouth.
If one develops or uses a simpler or more reliable—and equally (or more) economical solution, I’d be honored to invite an article on the subject in this forum.
Update (2/14/2021): The CDC is now recommending that people wear face masks correctly, covering mouth and nose, without gaps. They recommend typing a knot in the ear loops, and tucking in the gaps, as shown in the following video: https://www.prevention.com/health/a35480274/how-to-make-face-mask-fit-better-covid-19/
After a multitude of attempts I concluded that this method does not work for me.
Other photos and videos which I’ve seen show health care workers twisting the loop once, placing the bottom loop on the top of the ear, and the top loop on the bottom. In these videos, there a 1″-wide gap in the mask on each cheek.
My rubber-band method draws the mask closely to my face, and it never slips.
“The human face is, after all, nothing more nor less than a mask.” (Agatha Christie)
Making a Facemask Fit Perfectly
Paul R. Yarnold, Ph.D.
January 27, 2021