Read on Twitter
1/21 What am I up to? Just testing 5 PAPRs against each other as is normal. All of these offer a high level of protection except one. Highly relevant to the #PAPRbuggy #pramPAPR #PAPR 
2/21 As I have posted before some of the tests NIOSH performs on these is to make sure the air flow stays at 170lpm to maintain positive pressure and a filter test to see that it is 99.97% efficient. I have confirmed all of these stay at 170lpm with included air flow testers.
4/21 With a portacount I can back calculate the filtration efficiency from a fit factor. The fit factor is a ratio of particles inside and outside a respirator. How we calculate apparent filtration efficiency. 1-(1/FITFACTOR). We can say a FF of 3340 is 99.97%
5/21 Now to meet some of these devices. 3M TR-600. Approval: NIOSH. LPM >170. Filtration efficiency >99.97%. Cost to me($575, new open box) from ebay. The fit factors on these devices can reach MUCH higher depending on how you test but this is 99.99%.
6/21 Ford PAPR. Approval: NIOSH(emergency use). LPM: >170. Filtration efficiency >99.97%. Cost to me $130 (ebay). It is technically expired. Still works if you have ability to test the filter. Within limits of this test filter is assumed to be 99.99%+ efficient. Still works.
7/21 ADG Airboss Flexair. Approval: NIOSH. Some units w/ full approval, some limited. LPM >170. Filtration Efficiency >99.97%. Cost to me: $150 (Facebook marketplace). Within limits of my test: >99.99% efficient.
8/21 3M Versaflo TR-300. Approval: NIOSH. LPM >170. Filtration Efficiency >99.97%. Cost to me: ($500 new, open box ebay). Again, within limits of my test: >99.99% efficient. This one always scores the highest though the differences so far are insignificant.
9/21 Trudsafe "PAPR". Approval: None- *no one* has approved this or validated its protection or safety. LPM >170(per my testing). Filtration efficiency: ???. This the same configuration recommend in a scientific appearing paper widely shared on Twitter. This is our second test.
10/21 First let's review here: I tested this already and found it to have a FF of 4.2 aka 76% filtration efficiency- same score as my surgical mask from Costco. Definitely not real PAPR protection.
https://twitter.com/CriticalAerosol/status/1655328664115122176?s=20
11/21 Now for this test I checked all the connections for tightness & missing orings, replaced the filters. Gives a low fit factor of 12, about 91.6% filtration efficiency. Still well below the protection of an actual PAPR.
12/21 The Trudsafe accepts standard 40mm filters used by the military, police, & industry. I can not fathom why Twitter experts recommend either Chinese filters or 3M filters with an adapter that is a point for failure. It could leak or snap off entirely. Connection not secure.
13/21 Here we are with the ADG filters which are standard NATO 40mm. Suddenly we see fit factors in the hundreds. 385 here in a "realtime" test I can see effects of adjustments as I manipulate the device and filters. This not PAPR level protection but so much better.
14/21 Based on the tests of @FitTestMyPlanet we know that the device leaks. He used a truck bed liner spray to seal the device with risks of offgassing unknown to me so I wouldn't do that. I did place my finger over the charging port for a nice boost in fit factors!
15/21 To try and confirm the device was leaking in the frame I connected a drawstring bag to my TR-300 and placed it around the frame between the filters and the power button/charge port. Fit factor above 5,000 now PAPR level.
16/21 To try and get the level up there I wanted to try and seal it up with duct tape. Unfortunately not able to fully seal up all the leaks and I don't recommend this since it's temporary.
17/21 The proper way to fix this is to use a medical grade adhesive that is used for ventilator parts and has been tested to meet cytotoxicity limits. Unfortunately it may cost as much as or more than a Trudsafe. I am ordering some to try it.
18/21 If anyone has a Trudsafe I would replace it with *any* device with some form of NIOSH approval, especially if you can check airflow and replace filters you can make a better assumption it's offering some good protection. Ford filter can not be replaced/sourced at all.
19/21 It was unethical for so many twitter "experts" including at least 1 engineer to recommend this Trudsafe without having any method to validate its protection. A CPC such as a portacount is the only good way for a DIYer to verify. Would like to see retractions & updates.
20/21 Now that the pandemic emergency has been declared "over" it is common for PAPRs to be sold as surplus or overstock such as in government auctions, by fisher scientific etc. Will become more common. 40mm filters easy to source, can provide info.
21/21 Hopefully can soon offer some further information on sourcing of good devices and update on Trudsafe though I expect it to be cost prohibitive. Questions? DM's open.
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