Jeff Gilchrist
@jeffgilchrist.bsky.social
PhD Biomedical researcher, data scientist, and finder of large prime numbers. Views are my own. Twitter: @jeffgilchrist Mastadon: @jeffgilchrist@mstdn.science
COVID-19 guides, stats, calculators & 600+ scientific articles: http://covid.gilchrist.ca
COVID-19 guides, stats, calculators & 600+ scientific articles: http://covid.gilchrist.ca
It is possible that a specific headband respirator may have a worse fit on a person than a specific earloop respirator but in general the two straps around the head tend to pull better in the required direction to make and keep a better fit.
October 25, 2025 at 7:47 PM
It is possible that a specific headband respirator may have a worse fit on a person than a specific earloop respirator but in general the two straps around the head tend to pull better in the required direction to make and keep a better fit.
But many earloops look more like this where the fit factor is more in the <6 range ( www.testtheplanet.org?pgid=kcyqfc6... ). 3/
Home
www.testtheplanet.org
October 25, 2025 at 3:18 PM
But many earloops look more like this where the fit factor is more in the <6 range ( www.testtheplanet.org?pgid=kcyqfc6... ). 3/
For example here is the Breatheteq KN95 small which is all over the place ranging from 1.6 to 500 depending on the person ( www.testtheplanet.org?pgid=kcyqfc6... ). 2/
Home
www.testtheplanet.org
October 25, 2025 at 3:16 PM
For example here is the Breatheteq KN95 small which is all over the place ranging from 1.6 to 500 depending on the person ( www.testtheplanet.org?pgid=kcyqfc6... ). 2/
Although fit it very specific to each individual there is some fit test data from multiple people for a variety of different masks/respirators that you can check out here ( www.testtheplanet.org ). 1/
Test The Planet | Adversarial Quantitative Fit Test Data
TestThePlanet an open source movement aggregating and displaying live updates of motion resilience tests of all available respirators with adversarial protocols such as Crash2.5 for a growing communit...
www.testtheplanet.org
October 25, 2025 at 3:16 PM
Although fit it very specific to each individual there is some fit test data from multiple people for a variety of different masks/respirators that you can check out here ( www.testtheplanet.org ). 1/
They could be, some fit better than others and lots do not have very high fit factor on many people, especially when moving/talking. Unless tested, would be more cautious with an ear loop no matter what the standard they conform to.
October 25, 2025 at 3:06 PM
They could be, some fit better than others and lots do not have very high fit factor on many people, especially when moving/talking. Unless tested, would be more cautious with an ear loop no matter what the standard they conform to.
* Fit Testing to ensure a good seal on your mask [Part 2]: ( pingthread.com/thread/16553... ) 23/
Thread by jeffgilchrist: Fit Testing to ensure a good seal on your mask [Pa... - PingThread
Fit Testing to ensure a good seal on your mask [Part 2]
This thread describes my quantitative fit testing experience with some real-world results of various types of #masks including #NIOSH #N95 and ...
pingthread.com
October 25, 2025 at 11:09 AM
* Fit Testing to ensure a good seal on your mask [Part 2]: ( pingthread.com/thread/16553... ) 23/
* Fit Testing to ensure a good seal on your mask [Part 1]: ( pingthread.com/thread/16523... ) 22/
Thread by jeffgilchrist: Fit Testing to ensure a good seal on your mask [Pa... - PingThread
Fit Testing to ensure a good seal on your mask [Part 1]
This thread explains what mask fit testing is (qualitative and quantitative), why it is important, and my testing experience with some real-wor...
pingthread.com
October 25, 2025 at 11:09 AM
* Fit Testing to ensure a good seal on your mask [Part 1]: ( pingthread.com/thread/16523... ) 22/
* Why can you still smell things wearing an effective mask? ( bsky.app/profile/jeff... ). 21/
October 25, 2025 at 11:09 AM
* Why can you still smell things wearing an effective mask? ( bsky.app/profile/jeff... ). 21/
People who are interesting in learning more about how respirators work and what is fit testing and fit factors, the following resources are available:
* How respirators actually work and which type is best? ( docs.google.com/document/d/1... ) 20/
* How respirators actually work and which type is best? ( docs.google.com/document/d/1... ) 20/
How respirators actually work and which type is best?
How respirators & filters actually work and which type is best? Written by: Jeff Gilchrist, PhD Link to this document: https://tinyurl.com/HowMasksActuallyWork Last updated: February 2, 2025 I see ma...
docs.google.com
October 25, 2025 at 11:09 AM
People who are interesting in learning more about how respirators work and what is fit testing and fit factors, the following resources are available:
* How respirators actually work and which type is best? ( docs.google.com/document/d/1... ) 20/
* How respirators actually work and which type is best? ( docs.google.com/document/d/1... ) 20/
The other tab is "Fit Factor Calculator" lets you enter your own results from a fit testing exercise and calculates the overall fit factor score which can be used for a comparison with other fit factors. 19/
October 25, 2025 at 11:09 AM
The other tab is "Fit Factor Calculator" lets you enter your own results from a fit testing exercise and calculates the overall fit factor score which can be used for a comparison with other fit factors. 19/
The main point is that there is a huge different in exposure time going from no mask or a baggy blue procedure mask to a head band N95, even if it just passes fit testing, while many like myself can get a much higher fit factor than the pass rate. 18/
October 25, 2025 at 11:09 AM
The main point is that there is a huge different in exposure time going from no mask or a baggy blue procedure mask to a head band N95, even if it just passes fit testing, while many like myself can get a much higher fit factor than the pass rate. 18/
This is just one set of scenarios, you can adjust it to whatever you want to compare. 17/
October 25, 2025 at 11:09 AM
This is just one set of scenarios, you can adjust it to whatever you want to compare. 17/
When I had my 3M Aura fit tested, I got over 500 for the fit factor which would boost that time to 2500 minutes (41 hours) before equivalent exposure assuming that fit factor stayed constant throughout the time period. 16/
October 25, 2025 at 11:09 AM
When I had my 3M Aura fit tested, I got over 500 for the fit factor which would boost that time to 2500 minutes (41 hours) before equivalent exposure assuming that fit factor stayed constant throughout the time period. 16/
If you jump to an N95 respirator with a headband that just passes a fit test so the fit factor is 100, that would increase the time to 500 minutes (8.3 hours) before equivalent exposure to an unmasked person. 15/
October 25, 2025 at 11:09 AM
If you jump to an N95 respirator with a headband that just passes a fit test so the fit factor is 100, that would increase the time to 500 minutes (8.3 hours) before equivalent exposure to an unmasked person. 15/
Some ear loop respirators get a fit factor of about 6 which means it would be 30 minutes before a similar exposure, and other ear loop respirators can be higher or lower depending on the fit for your face. 14/
October 25, 2025 at 11:09 AM
Some ear loop respirators get a fit factor of about 6 which means it would be 30 minutes before a similar exposure, and other ear loop respirators can be higher or lower depending on the fit for your face. 14/
Procedure masks (baggy blue) on many people will only filter about 50% of particles so if it only takes 5 minutes for an unmasked person to become infected, then that time doubles to 10 minutes to get an equivalent exposure of virus with a baggy blue. 13/
October 25, 2025 at 11:09 AM
Procedure masks (baggy blue) on many people will only filter about 50% of particles so if it only takes 5 minutes for an unmasked person to become infected, then that time doubles to 10 minutes to get an equivalent exposure of virus with a baggy blue. 13/
The graph shows a fictitious high COVID concentration example of 3 scenarios where someone without a mask could get infected from COVID within 1, 5, and 10 minutes along with various fit factors (FF). 12/
October 25, 2025 at 11:09 AM
The graph shows a fictitious high COVID concentration example of 3 scenarios where someone without a mask could get infected from COVID within 1, 5, and 10 minutes along with various fit factors (FF). 12/
There are two tabs, "Equivalent Exposure Time Calculator" that lets you compare multiple # minutes to infection time scenarios against multiple fit factors which you can adjust for the scenarios you are interested in comparing. 11/
October 25, 2025 at 11:09 AM
There are two tabs, "Equivalent Exposure Time Calculator" that lets you compare multiple # minutes to infection time scenarios against multiple fit factors which you can adjust for the scenarios you are interested in comparing. 11/
The calculator is available here ( docs.google.com/spreadsheets... ). 10/
Fit Factor & Impact Calculator
docs.google.com
October 25, 2025 at 11:09 AM
The calculator is available here ( docs.google.com/spreadsheets... ). 10/
A fit factor of 100 is the minimum pass rate for a fit test which means there are 100x less particles inside the mask than outside. A fit factor of 2 means there is 2x less particles inside or you could also say that 50% of particles are being filtered. 9/
October 25, 2025 at 11:09 AM
A fit factor of 100 is the minimum pass rate for a fit test which means there are 100x less particles inside the mask than outside. A fit factor of 2 means there is 2x less particles inside or you could also say that 50% of particles are being filtered. 9/
...and it will show you how much longer it would be to have an equivalent exposure for various fit factors of masks based on how much filtration they are performing. You can adjust the # of minutes, and also input different fit factors. Some example fit factors are provided to get you started. 8/
October 25, 2025 at 11:09 AM
...and it will show you how much longer it would be to have an equivalent exposure for various fit factors of masks based on how much filtration they are performing. You can adjust the # of minutes, and also input different fit factors. Some example fit factors are provided to get you started. 8/
To make things more flexible so that you can look at various scenarios for the specific situations you are interested in comparing, I have created a couple of calculators that let you input and decide how many minutes it would take to become infected without a mask... 7/
October 25, 2025 at 11:09 AM
To make things more flexible so that you can look at various scenarios for the specific situations you are interested in comparing, I have created a couple of calculators that let you input and decide how many minutes it would take to become infected without a mask... 7/
The popular 3M Aura 1870+ for example had an 88.9% pass rate for women and 97.6% pass rate for men in this study so for personal use it is very likely to be better than a baggy blue procedure mask even without a fit test ( pmc.ncbi.nlm.nih.gov/articles/PMC... ). 6/
Quantitative fit-test concordance of a pair of similar-fit 3M Aura respirator models, 3M 9320A+ and 3M 1870+: A randomized crossover study
Some manufacturers provide information on similar-fit model pairings of filtering facepiece respirators (FFRs), suggesting that fit-test outcome of one model helps predict the other. This guidance may be useful during crisis capacity when FFR ...
pmc.ncbi.nlm.nih.gov
October 25, 2025 at 11:09 AM
The popular 3M Aura 1870+ for example had an 88.9% pass rate for women and 97.6% pass rate for men in this study so for personal use it is very likely to be better than a baggy blue procedure mask even without a fit test ( pmc.ncbi.nlm.nih.gov/articles/PMC... ). 6/