Can tiny nostril filters protect you from Covid?

Lots of people would like unobtrusive respiratory protection, and nostril filters are an attractive option, or they *could be* if they work, and if you only breathe in through your nose.

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I was given these by Amazon to review. They are from O2 Armor, who provide more filter data than most companies. But check their wording and compare it to their filtration efficiency graph..."up to" is doing a lot of heavy lifting.
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You can see in these macro photos how loose the weave of the nostril filter is to make it breathable at such a small size. Compare that to the Drager N95 filter shown at the same magnification.

Electrostatic attraction can make a filter work better than it looks, however...
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I got the perhaps lowest filter-only score I've ever tested:

Fit Factor 1.2
17% filtration efficiency

(I made a jig to test the nostril filters directly with a PortaCount at 0.7 liters of airflow per minute. Penetration would be way higher at the 85 lpm NIOSH test airflow.)
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The 17% filtration efficiency score is consistent with seller's filtration efficiency chart and the sub-micron counting range of the PortaCount.

Better than nothing, but not much. So avoid risk compensation and don't take on any extra risks if you use these. Image
Wear a good respirator that fits you well instead of nostril filters when at all possible. The difference in protection is orders of magnitude.

3M Aura and Drager trifold N95s are good respirators to try that fit most, but not all, people well and are very protective. Image
I didn't test these in my nose because there isn't a way to sample the air above the nostril filters short of a big nose piercing, so I didn't test fit, just filtration. More on that in a later Tweet.
O2 Armor have a pretty detailed write up with test data. They seem to come to opposite conclusions about the utility of their nostril filters based on that data than I do.

static1.squarespace.com/static/6064fce…

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More from @ghhughes

Dec 7, 2024
Do N95s and KN95s filter viruses?

Yes.

Here's an electron microscope image of salt particles on the fibes of a KN95 by @zhouliang_mask.

The image is of a NIOSH-type salt loading test of the melt blown filter media used in Zimi 9541.

The "big" crystals are about 1.5 microns. The smaller captured particles are as small viruses like Covid.

Covid virions are about .07 microns, are expelled into the air in larger respiratory droplets.

reddit.com/user/zhouliang…Image
If you are thinking, that's just salt, not viruses, not to worry. Scientists have tested N95s using real viruses using an international standard test called Viral Filtration Efficency (VFE). N95s filter viruses extremely well.

x.com/search?q=n95s%…
N95s can filter extremely small particles thanks to multiple mechanisms, including electrostatic attraction.

This video does a great job of how N95 filter media works to filter a wide range of particles.

Read 6 tweets
Nov 5, 2024
Can you make a cheap Amazon Plague Mask into an effective tight fitting PAPR mask?
Yes, yes you can. If you happen to already have a bunch of stuff everyone totally has lying around their home:

Honeywell 700 PAPR blower

Honeywell PA034L Y Adapter

Honeywell 5500 Series 1/2 Mask Respirator

youtube.com/shorts/QYuSbgE…Image
I've also done a 4 exercise OSHA fit test in this hacked Plague PAPR mask and passed - well, I got a great fit factor but the hacked mask isn't OSHA compliant, nor is fit testing a PAPR with the blower on, so some might say it didn't pass. 🤔
I may put together a longer video in horizontal format, the one I originally shot, but I'm trying to make my videos less boring and am giving YouTube shorts a try. 😅
Read 7 tweets
Sep 23, 2024
More from @NIOSH's Respiratory Protection Week presentation by Susan M. Moore, NPPTL Associate Director for Science:

Respirator fit solutions for people with beards.

The Singh Thattha technique can help, but it is not yet OSHA approved. NIOSH is studying this method. PowerPoint Slide:  "Established partnerships to evaluate potential interventions for workers unable to remain clean-shaven • Partners: Sikh Coalition, Equal Employment Opportunity Commission, OSHA • OSHA Regs: users to be clean shaven for tight-fitting respirators • Potential intervention: “beard band” • Federal Register Notice: seeking additional partners - Partnership Opportunity To Determine the Fit of Air Purifying Filtering Facepiece Respirators Worn Over Beard Bands for Workers With Facial Hair (deadline: Sept 23, 2024) • Protocol: quantitative fit measurements - Respirator Fit C...
Currently OSHA fit test regulations require smooth skin at the respirator seal, as shown in this graphic.

But some people have beards for cultural, religious and even health reasons that are incompatible with those regulations. Solutions are needed for equitable safety. A graphic with illustrations of 35 different facial hair styles and one clean shaven face. Clean shaven and other select styles that have smooth skin at the respirator seal have a green check mark. Those with facial hair over the area of the mask seal have a red X.
Facial hair has a demonstrable effect on respirator seal and protection, and some masks work better with facial hair than others even without special methods to improve the seal, but it isn't really about whether they are KN95 or N95 or KF94, but individual mask models and design A graph of fit testing different beard lengths and different masks. The best fit is the N95, followed by the KF94 and KN95. As facial hair length increases, performance gets worse.  The cloth mask and surgical masks perform so poorly there is no difference in performance with increases in facial hair length.
Read 12 tweets
Sep 10, 2024
Thoughts about @NIOSH's Respiratory Protection Week presentation by Susan M. Moore, NPPTL Associate Director for Science:

The presentation showed current and future source control respirators, including a NIOSH exemplar model source control elastomeric mask for HCWs. Slide with images of source control respirators:  Text: "Advanced elastomeric half mask respirator (EHMR) designs to meet the needs of HCP  Source control: coordinated with NIOSH approval holders during COVID-19 pandemic to approve EHMR configurations without exhalation valves or filtered exhalation  Re-usable healthcare elastomeric respirator: considered filter media, computational fluid dynamics modeling, and HCP design input to develop a healthcare-focused EHMR prototype [bench testing pending]  NIOSH approval holders or applicants are responsible for applying to NIOSH and gaining a...
I was glad to see elastomeric source control respirators highlighted. Dr. Moore referenced industry creating source control elastomerics for the pandemic. But the 3M mask with the exhalation filter shown is a bit of a mixed bag.

3m.com/3M/en_US/p/d/v…

Detail from slide. The 3M 6000 series half mask with 604 exhalation valve filter has been highlighted with a yellow oval.
Woman wearing a 3M half mask respirator with optional 604 Exhalation Valve Filter
3M created an exhalation filter that fits on a single model of 3M mask, the 6000 series half mask respirator, a good but lower end model with no speech diaphragm. The filter was a good emergency stopgap, but not a good long term solution.

multimedia.3m.com/mws/media/1838…
Read 10 tweets
Aug 16, 2024
ReadiMask is still selling old stock stick on N95mmasks from ~4 years ago, made before NIOSH approval with no warning about whether the adhesive may have degraded over time.

How old is the other mask stock they are selling? And has the adhesive degraded?

readimask.com/collections/re…
The Readimasks I have don't seem to be adhering as well as when I bought them. I managed to supplement the adhesive with Mastisol liquid adhesive supplied by @findmeabluebird, but I'd like Readimask to be more transparent about the age of their stock.

eloquesthealthcare.com/mastisol/
Is there a way we can monitor how well the adhesive is holding up over time? Can we objectively measure how the adhesion? This standardized method looks good but seems very expensive. And I'm not sure if stainless steel is analogous to skin.

Read 4 tweets
Jul 6, 2024
Are valved masks cooler? I tested 3 different 3M N95s to try to learn more about the effect of valves on heat in respirators.

Not much mathematical difference on average, under these specific conditions, with these 3 masks:

V-Flex +7.3°C
Valved Aura +7.3°C
No Valve Aura +7.5°C Image
I expect that results could vary dramatically under different conditions, including temperature, humidity, airflow rate, mask model and more. Even so, I was surprised that the valve didn't make a more substantial difference in average in-mask temperature.
I also tested valved and unvalved Auras during 15 minute outdoor walks in mixed shade and sun and got a similar lack of difference in average in mask temperatures (using different testing gear with 10 second intervals between samples). Image
Read 7 tweets

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