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Gerard Hughes ( @ghhughes@zeroes.ca ) Profile picture
Gerard Hughes ( @ghhughes@zeroes.ca )
@ghhughes
Science and critical thinking fan. Not actually a cat. He/him. https://t.co/FxeHdPFaMz Mastadon: https://t.co/9uo4UEM9XU The B--- site: @ghhughes
3 subscribers
Dec 7, 2024 • 6 tweets • 2 min read
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%…
Nov 5, 2024 • 7 tweets • 2 min read
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. 🤔
Sep 23, 2024 • 12 tweets • 4 min read
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.
Sep 10, 2024 • 10 tweets • 3 min read
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
Aug 16, 2024 • 4 tweets • 2 min read
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/
Jul 6, 2024 • 7 tweets • 2 min read
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.
Jun 17, 2024 • 5 tweets • 1 min read
Testing the AIRfanta Lite4 - the full length video.

I used several kinds of testing machines to characterize the amount and location of protection this portable laminar flow air purifier @Engineer_Wong sent me for review.

The video has a PortaCount test as well as the AeroTrak test - they measure different sized particles. I used a different particle range in the AeroTrak graph in the video than the one I posted on Twitter earlier, but they both illustrate the on vs. off axis protection levels.
Jun 14, 2024 • 7 tweets • 2 min read
Can a special laminar air purifier protect you where you have to go maskless, or let you take off your respirator where you normally would not?

@Engineer_Wong sent me an AIRfanta 4Lite to try out.

Tests showed the near field protection to be narrow, and less than mask level. Image I used an optical particle counter to confirm my PortaCount measurements, and the results are similar.

This bubble chart shows how the count of particles even slightly off-line of the center axis of the air flow is higher.

(Unfiltered ambient count upper left.) Image
Oct 31, 2023 • 10 tweets • 4 min read
8 of the top 10 hits on Amazon for "respirator" are copies of the 3M 6200. Are they safe?

I tested one Amazon sent me for review, and the results are far worse than I expected: a 33% leak.

Don't trust generic respirators to protect your health. Image The mask fit test results:

Generic 6200 Fit Factor: 3

Genuine 3M 6200 Fit Factor: 9612

The 3M performed 3204 times better than the copy.

Another 6200 copy tested better: FF 27. Still short of the needed min. of 100.

All copies tested significantly lower than genuine 3M.
Image
Image
Oct 24, 2023 • 10 tweets • 4 min read
Can a black KN95 over a 3M Aura, as seen worn by @ModelAyshaMirza, pass a fit test ?

Short answer: Yes, it can. It did on me.

Longer answer: Fit is very individual. You'll need your own fit test to know. Double masking often reduces fit a bit, but can also improve it. YMMV. A mannequin head with black KN95 worn over a 3M Aura. For illustration purposes. The masks were tested on me and not the mannequin. To test this double masking configuration, I first tested the 3M Aura 9205+ worn normally on my face by itself. I used a PortaCount in N99 mode.

Full OSHA N99 mode fit factor: 355

That essentially means the air inside the mask is 355 times cleaner, total inward leakage 0.3%.
A mannequin head with wearing 3M Aura 9205+ N95. For illustration purposes. The masks were tested on me and not the mannequin.
Image
Oct 23, 2023 • 8 tweets • 4 min read
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.

🧵
Image
Image 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.
Image
Image
Oct 10, 2023 • 5 tweets • 2 min read
Beware of Amazon Big Prime Deals on Respirators.

The top discounted respirators are part for part copies of 3M half masks. They have the appearance of a NOSH approved 3M respirator, but without the performance or quality control. Image There are some genuine NIOSH approved respirators on sale at Amazon, including some 3M, but you have to look carefully. The copies look identical and even have the same model numbers, but *usually* don't have the 3M or NIOSH logos. Image
Sep 14, 2023 • 8 tweets • 2 min read
CleanSpace PAPRs are perma-dead when the rechargeable battery dies.

There is service for dead or dying batteries out of warranty. So don't count on your unit lasting longer than the warranty period.

They are great tools, but have a limited lifespan. Image The CleanSpace rechargeable batteries can die permanently even if you just are storing the PAPR, as a number of people found out when they bought discontinued CleanSpace2s from Fisher Scientific with dead batteries. Fortunately, those customers were made whole, eventually.
Aug 22, 2023 • 12 tweets • 5 min read
What can you do if you have to have dental treatment, but don't have access to a dental office that masks?
A stick on nose-only mask can help reduce your exposure to airborne hazards.
I tested a few nose-only hacks and compared them to masks worn normally. They did help.

1/🧵 Image The best performing hack was @findmeabluebird's way of using a stick on ReadiMask N95 as a nose-only mask. I tested it with an 8 exercise fit test and got a bit lower score than I did with a single exercise test a while ago, but it is still protective.





Fit test results for the acrylic adhesive version of a medium sized ReadiMask worn over the nose only: 25 The acrylic version tested much better than the silicone adhesive version except in the talking test. It stuck better to my skin so I don't know how the talking test got a lower score. This was a full 8 exercise OSHA fit test in N99 mode, sample tube held by hand to reduce the possibility of interfering with the mask seal.
A medium silicone adhesive ReadiMask shown worn over the nose of a mannequin. The mask was fit tested on my actual face. The photo is just for illustration purposes.
A medium acrylic adhesive ReadiMask shown worn over the nose of a mannequin. The mask was fit tested on my actual face. The photo is just for illustration purposes.
Fit test results for the silicone adhesive version of a medium sized ReadiMask worn over the nose only: 26 I bought this silicone ReadiMask last year. It would not stick to the clean skin of my nose bridge *at all* until I wiped my skin down with rubbing alcohol. The acrylic version stuck to my skin much better and tested much better than the silicone adhesive version except in the talking test. This was a full 8 exercise OSHA fit test in N99 mode, sample tube held by hand to reduce the possibility of interfering with the mask seal.
Jul 31, 2023 • 11 tweets • 4 min read
I just got this adorable little powered "OFG Fresh Air" respirator from Amazon. It is slightly different than others I've seen.

It would be so much smaller and more convenient than an industrial powered respirator if it works.

So I tested it to find out.

🧵 Image First, I fit tested it with the blower turned off.

The supplied black KN95 leaked a lot at my nose bridge - no surprise since it has a weak twist tie-style nose wire.

The test results? An unsurprisingly crappy N99 mode fit factor of 3.
Air is only 3x cleaner inside the mask. Image
Jun 27, 2023 • 15 tweets • 5 min read
There is confusion about how N95 masks are fit tested using PortaCounts.

PortaCounts measure the concentration of particles .02 microns to 1 micron inside and outside the mask. The reduction of concentration from outside to inside is called the "Fit Factor".

1/ The maximum seal leak allowed for a fit test is 1%. But N95s are allowed to have up to 5% filter penetration.

How do you test for a 1% seal leak for a mask that is allowed to let up to 5% of particles in?

2/
Dec 23, 2022 • 4 tweets • 2 min read
How do we know Saccharine and Bitrex Fit testing works? It's validated against particle count fit testing.

Here's a cool history of the development of Bitrex fit testing by 3M, which was created with the brief to be less pleasant than Saccharine but safe

multimedia.3m.com/mws/media/2241… Article header: Development of a new qualitative fit test us Here is the validation study.

2 masks passed Bitrex testing that should have failed. 12 masks failed Bitrex testing that should have passed. Saccharin results were identical.

2/ A table comparing the pass rate of a quantitative particle c
Dec 22, 2022 • 7 tweets • 2 min read
A new study shows 87% still pass a fit test when they put a surgical over their 3M Aura N95.

13% did not, illustrating the importance of fit testing your respirator exactly as you will be wearing it.

That's my take on the study.

cidrap.umn.edu/covid-19/study…

1/ The 100 subject study did not capture the fit factors of the Aura-only tests or the Aura + Surgical tests, so the study data does not show how much change in FF there was, or whether any was positive – authors just assume negative delta is the only possible outcome.

2/