Constructing a Face Mask with a Polypropylene Lining

There’s quite a bit to cover (pun intended), so let’s start with the basics. A quality face mask needs to check the boxes in three categories: filter media, facial coverage and fit . Here’s the information you need to properly evaluate whether a mask makes the grade.

Quality Materials

According to the CDC, tightly woven cotton is the material of choice for a face mask shell. Cotton is breathable, and retains strength and softness at high thread counts, so it’s a great material for the shell of a mask. The WHO recommends cotton on the back, but suggests using a poly-blend for the front surface.

Most masks on the market these days are 100% cotton, but open them up and you’ll start to see some stark differences that have a huge impact on overall quality and protection. You'll especially notice the difference when comparing a non-protective mask to a high performance mask meeting the new CDC-recommended ASTM F3502 standards.

What you don't want to see when you cut open a mask - especially if you're using it without a filter - is nothing between the inner and outer layers. A lack of filling material - typically batting - means there’s nothing to wick away moisture or provide an electrostatic barrier to stop ultra-fine particulates.

An alternative to batting, frequently found in high-end masks in countries with a high amount of airborne pollution, is a thin layer of apertured (precisely perforated), spunbond (nonwoven) polypropylene film (let’s just call it “PE”). Quality PE allows air to pass through easily but blocks the majority of moisture the bacteria and germs that tend to travel with it. Like most materials, there’s a lot of variability in quality (just like with carbon pm2.5 filters ).

A properly apertured PE layer should remain impermeable to moisture for an extended period of time. Watch the difference between high-quality PE (right) and low quality PE (left) when water is directly applied to the surface of the material.

(The video states "polyethylene"... but that was our mistake.)

Nose-to-Chin Coverage



If you “batted” an eye at the reference to the fabric under the chin, you’re not alone. This is an essential part of the second important category, coverage, but it’s often missed.

A face mask should extend from the bridge of the nose - secured with a nose clip - to below the chin. This is partially a function of fit, which we will cover last, but it’s also a function of the mask’s structure, or how it’s designed. Lengthwise, it should extend from ear-to-ear. Here’s a now-famous example of two masks that both fit just fine, but with very different coverage factors:

Fit



We’ve said it before, and we’ll keep saying it: the single most important aspect of an effective mask is a good fit. Because very few people could or would pay for a tailored face mask, it’s important that a mask be as adjustable as possible. Besides starting with a mask that is most closely sized to your face, a good mask should have these two fit elements: adjustable elastic ear straps, and a malleable nose clip.

The malleable nose clip serves a double function of achieving a better seal around the bridge of your nose, while also helping prevent your glasses from fogging up when wearing your mask.

Finally, it’s important to remember fit isn’t just about minimizing gaps between your mask and your face… it’s also about comfort, which happens to be a huge factor for safe mask use. Researchers studying the effectiveness of N95 respirators during a pandemic concluded a primary reason healthcare professionals who wore N95 masks got infected anyway is because the masks were so uncomfortable that the wearer is frequently making small adjustments for a more comfortable fit, or even taking the mask off altogether. It's true.... comfortable masks save lives!

Putting it All Together

For quick reference, here are all the elements we talked about above in one place. Think of these as the “Essentials”... and don’t settle for anything less.

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Here at Puraka we’ve been talking a lot about apertured polypropylene recently (although it's  not a phrase we'd use as a conversation starter). We love how it’s breathable and lightweight on one hand, with excellent filtration and moisture resistance on the other. In fact, we think it’s so great that we decided to incorporate it into our Essential line of masks as a standard middle-layer. You can browse all of our masks here .

Learn more about the benefits of multi-layered masks with carbon pm2.5 filters at purakamasks.com