I’ve been hoarding my three N95 masks, left over from the Camp Fire, reserving them for an emergency, what if I must use a hospital or an airplane (imagine putting those two locales in the same category back in the olden days, AKA last year). But I might not need to strictly conserve those precious N95 for an emergency I hope never happens because a new study determined how to clean N95 masks using an Instapot (or other electric cooker).
I began the pandemic assuming that the supply problem with masks and other PPE would be resolved in a few months and we’d be able to buy quality masks. However, since the government has routinely failed to take suitable actions on other issues, I’ve also been gathering mask information.
- Which mask is best, given what is available.
- What kind of filter material provides the most protection.
- How should we care for reusable masks.
Before sharing all the best mask advice, here’s a reminder from KosAbility about our monthly meeting on Sunday August 30th at 4pm PDT (7pm EDT). For our meeting, elenacarlena has a diary about how to get an elderly person off the floor after a fall. As usual, our meeting will be an open thread with room and time for what you wish to bring to the comments.
Most of us have already realized that masks are important to prevent the spread of COVID-19 from infected people and that specialized masks like N95 will also protect the wearer. But let’s not forget that this protection is a reduction of risk, not an elimination. Most homemade masks are much less personal protection than precious N95 masks that filter up to 95% of contaminants. Homemade masks, however, can significantly reduce the risk of the wearer spreading the virus and some mask designs also protect the wearer from picking up pathogens. The different levels and types of protection from various mask styles and materials can guide us in designing our personal protection. Generally, more layers of homemade mask material result in greater protection of both exhaled virus (spreading from the mask wearer) and inhaled (coming through the mask to the wearer), although the particular material type and fit is also important.
An exterior view of my homemade masks (not made by me!). Note the center stitching that helps shape the mask. A filter in a pocket on the inside covers the holes made by that stitching.
This article is from Australia where people have the option to use both surgical masks and cloth masks. The main points for best protection from a cloth mask are the following.
- A single-layered mask is better than no covering, but two layers are better than one, and three layers are better than two. More than three layers are better still.
- ”Look for a fine weave, high thread count and dense material. Flimsy or see-through material, or material with large gaps, is not adequate because droplets and aerosols can pass through the gaps.
- ...pure cotton is not a good choice for the outer layer, as it is absorbent. If someone else is coughing and sneezing near you, you want your mask to block those droplets rather than enable them to pass through the mask and infect you. A polyester or cotton-polyester blend is a better choice for this outer layer.
- If a drop of water on the outside surface is absorbed straight away, that's a fail. If the drop forms a bead, the mask is water-resistant.
Regardless of the type of mask, it’s important to ensure a snug fit.
The World Health Organization (WHO) recommends using three layers of fabric for non-medical, cloth masks in order to achieve the best combination of filtration efficacy and breathability:
1. Innermost layer: Hydrophilic material (i.e., one that can absorb moisture, such as cotton or cotton blends)
2. Middle layer: Hydrophobic material (i.e., repels moisture) of synthetic non-woven material such as polypropylene or a second cotton layer which may enhance filtration or retain droplets.
3. Outermost layer: Hydrophobic material (e.g., polypropylene, polyester, or their blends) which may limit external contamination from penetration through to the wearer's nose and mouth.
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Note that polypropylene, a material often used to make disposable surgical masks, has an electrostatic charge which can improve the filtration efficiency of masks. Polypropylene "spunbound" is sold in fabric and many other retail and online stores under brand names such as Oly*fun and Pellon. Polypropylene is sold in different weights (measured in grams per square meter or GSM). Most commercially manufactured surgical masks are made of 3-ply 25GSM. Polypropylene materials between 25 and 40 GSM tend to have similar filtration efficacy and breathability, while polypropylene 60 GSM has a higher filtration efficiency but less breathability (Zhao, Nano Lett 2020). Be aware that some forms of polypropylene should not be machine washed.
Consumer Labs also shares warnings against two types of masks that aren’t much help (bandanas) or even make the risk of spread worse (fleece materials).
Two masks offered little protection: A double-layer bandana was only slightly more effective than using no face covering at all, while the worst face covering was a "gaiter" style neck fleece (often worn during running or sports) that showed a 10% increase in the number of droplets. The researchers suggested that the neck fleece material breaks larger liquid droplets into smaller droplets than can more easily be dispersed into the air (Fischer, Sci Adv 2020 — includes photos of the masks but no details about origin or brands).
No matter what material is used, a neck gaiter style mask is dangerous to the wearer because each time you let it drop or pull it over your head to remove, you contact the potentially contaminated inside and outside areas. Another mask type that isn’t protective of others are those with respirators because the wearer’s breath (and virus particles) is exhaled through the respirator valve.
Nose Clips For homemade cloth masks, the best design is a multi-layer fitted mask of suitable materials with a nose clip. The masks I use have a tunnel across the nose bridge and I bought aluminum strips from Amazon that slide into the tunnel — 100 strips for $8. These are reusable and have survived the washing machine when I forget to remove them first.
Inside view of my mask showing the tunnel (white strip at top of mask) for the nose clip, the aluminum peeping out of the tunnel — also the unused strip lying vertically at the left side of the mask. A PM2.5 charcoal filter is shown on the left partly slipped into the filter pocket.
Insertable Filters Another way to improve the protection in homemade masks is to use filters inserted into a pocket on the face-side of the mask. Consumer Labs also has information on filters.
...the WHO recommends that the middle layer of a cloth mask be made of a synthetic, nonwoven fabric such as polypropylene, or a second layer of cotton (high thread count cotton has been shown to have better filtration efficacy than lower-thread cotton). Many cloth masks that you can buy online come with a "filter pocket" as the middle layer, which you can buy pre-made filters for, or add your own. We've reviewed common materials for making mask filters, including Filti Face Mask Material and Medline Dry Baby Wipes, as well as materials such as polypropylene and other non woven fabrics (100% polypropylene, Pellon Sew-In Interfacing and Oly*fun), cotton and quilter's cotton
I learned about these filters a few months ago and found an online source for polypropylene precut to fit in homemade masks for a bit over $1.00 each. That seemed like a good deal to me back when I thought better masks would be available commercially after the supply crunch had been addressed. We all know now this wasn’t done and we’re still on our own for masks, so I intend to locate a source for the uncut material that is more economical.
This article has more filter information and sources, including the carbon PM2.5 filters I bought at the beginning of lockdown in March before upgrading to the polypropylene filters. NOTE THAT THE PM2.5 CARBON FILTERS ARE FOR PARTICULATES AND DO NOT FILTER OUT CORONAVIRUS.
The two types of filters I use. On the left are the front (yellow) and inside (white) of a polypropylene filter. The right shows two PM2.5 charcoal filters.
This Consumer Lab info roundup addresses how to wash or decontaminate masks, including the N95. (Here’s the scientific paper cited in the text below that studied using dry heat to decontaminate N95 masks for reuse.)
A study by researchers at Stanford University found that heating N95 masks (known as respirators) at 167°F (75°C) for 30 minutes (at 85% relative humidity) did not compromise the masks, even after 20 cycles — although these researchers have subsequently cautioned that contaminated masks should not be brought into homes. (If you use an N95 respirator, you may want to watch a video from the New England Journal of Medicine that instructs health care workers on how to properly put on, take off, and test the fit of such masks and other personal protective equipment.)
is there anything an instapot cannot do? (Other similar cookers, like an electric rice pot, also work)
SOME IMPORTANT DO NOTS
- Don’t get N95 masks wet, or use liquid cleaning materials (e.g., hydrogen peroxide) on them.
You should not soak N95 or surgical masks in disinfectants such as alcohol or other liquids as this can compromise their electrostatic charge (reducing their filtering capability) and fit (Interview with R. Shaffer, JN Learning 2020). Researchers at Stanford University found that immersing N-95 mask material in 75% ethanol or spraying with a household chlorine bleach solution (2% sodium hypochlorite) decreased the filtration efficiency (due to loss of electrostatic charge) to unacceptable levels after just one treatment, from about 96% to 56% and 73%, respectively.
- Don’t touch the mask when removing it. Grab the ear or head bands to remove it and fold the mask to keep the inside material together. Remember, the outside of the mask may be contaminated with virus.
- Don’t hang your mask from the rear view window in your car. Put it in a paper bag. After touching the mask, sanitize your hands.
Because I only need masks for grocery shopping events at the most responsible places (bless you Trader Joe’s and Chico Food Co-op) that occur at long intervals and a few other reasons I am in public areas like to walk from a parking area to a trail, I don’t wash my mask after each use. I put it in a paper bag in the car’s front window between the sunshade and the window so it is heated by the sun. By having several masks, I can allow a used mask to decontaminate in the heat for several days before reusing it. Cloth masks should be washed often, by hand or in a machine using soap. I discard the filter before each laundering.
All this advice can make us safer but MASKS ARE NOT MAGIC. Using all these researched methods to assemble and properly use your homemade mask will reduce BUT NOT ELIMINATE the risk of spreading or picking up COVID-19.
N95 is not as stylish as my nature-themed cloth masks but it offers a superior level of protection.