Thread by @antiviral_mktng

I made a Black Aura*.

I coated a 3M Aura 9210+ in Derwent Academy black water soluble marker, and measured the resulting fit factor using a PortaCount 8020A in N99 mode. There was no meaningful impact on performance.

* It came out gray. 🧵

I performed 3 sets of 3 normal breathing exercises wearing a 3M Aura 9210+ respirator, with a redonning in between each set. I then spent about 45 minutes coating the entire outer surface in Derwent Academy black marker.

And yes, it was exactly as satisfying as you'd think.

For this experiment I wanted to push the limits of modding to see if I could get the respirator to fail.

I could not!

I chose the Derwent Academy series of markers because they are vegan, and veganism is awesome.

I *mistakenly* thought they were advertised as nontoxic, but they are not. However their safety data sheet suggests they are unlikely to be toxic.

derwentart.com/a/328371

After coating the respirator in a layer of ink, I performed another 3 sets of 3 normal breathing exercises, with a redonning in between each set.

The result is astonishingly that there is no meaningful difference between the default and modified respirators.

Here are the harmonic mean fit factors (HMFFs) for each respirator for each set of 3 exercises, plus the overall HMFF for all 9 exercises. These represent the average leakage across all exercises.

I consider these results to represent identical performance between default and modded respirator.

This sort of fluctuation in minute-to-minute fit factor is absolutely common when testing a respirator.

I used redonnings in this experiment to partially control for the impact of donning on respirator fit.

It is possible that the marker could worsen Black Aura performance, but the second donning produces a superior fit, negating the marker's measured impact.

Multiple donnings in this experiment show that the fit is consistent across donnings, for both default and modded respirator.

Given that the fit is stable, and the Black Aura did not see worse performance, we can conclude that the marker does not meaningfully impact performance.

In this detailed view, you can see that the Aura's material appears debossed, and the marker's tip glides over the sunken areas. It also does not absorb ink as paper would. I suspect the fibers are not nearly as saturated as they appear at a distance, preserving performance.

A reminder that the amount of airflow through the respirator heavily influences the resulting score. If I breathe heavily, I can push my Aura score under 100. If I hold my breath for 60 seconds, I can push it over 1000.

For this reason, breathing rate is a semi-controlled variable in PortaCount experiments, and the resulting scores should be interpreted loosely.

What we're looking for here is an obvious difference between the two test conditions. And there isn't one!

The individual exercise scores for the default Aura ranged from 160-236. The scores for the "Black Aura" ranged from 157-226.

These sound like large fluctuations but this is just normal variation. They represent absolute differences of 0.20% and 0.19% leakage, respectively.

It's also important to note that face seal leakage dominates total leakage when wearing most respirators. This experiment is designed to answer the question: "If I get too carried away pimping out my respirator, should my friends intervene?"

In the this experiment, the HMFF of 9 normal breathing exercises was nearly identical between respirators.

The absolute difference was 0.02% leakage. This is easily explained by random variation.

They're the same! Shocking, but true!

So what can we conclude from this experiment?

Well, I'm flabbergasted. I was honestly expecting the performance to degrade. At least with this particular water-soluble marker, you can decorate as much as you want and I don't see any issue.

Unlike an OSHA style fit-test, these results will generalize to your face, since the mod is not structural and I am using my own face as a control. This is a fairly pure test of whether drawing on a respirator degrades performance enough to add meaningful leakage.

I am *medium* confident that this will generalize to pretty much every disposable respirator. I would like to see various markers tested on various models, but these results put another nail in the myth that respirators are fragile snowflakes.

However PLEASE, don't be reckless! 🙏

If you want to draw on your respi, do a Bitrex fit-test one time to verify your approach to modding is fine. Share your results with the community so we can all learn!

If you can't access Bitrex for whatever reason, I don't think you're taking a significant risk by drawing on your respi with a water-soluble marker.

However, it's not like we have a database verifying the safety of every marker. Use good judgment.

If there were any safety concerns regarding coating the outside of an Aura in velvety ink, I think this mitigates them.

Any drawing you are likely to do won't be as intense as what I just attempted! 😅

I should note, I was surprised to learn that these Derwent Academy markers contain 20% isopropyl alcohol by weight. It's flammable, so don't light your respirator on fire.

derwentart.com/a/328371

The study below shows 70% isopropyl alcohol degrades the electrostatic charge in respirator filters. The Derwent Academy markers contain less than 20%, possibly much less. I can only assume this is why the marker did not impact performance.

isrp.com/the-isrp-journ…

Okay, on to qualitative observations.

The marker doesn't smell. It has zero odor. That's good!

However, and this is pretty disappointing: it smudges like you would not believe.

After applying the ink, I allowed it to dry for an hour, but it will still rub off the respirator as if it were freshly applied. 😬

The ink gets all over your hands and stains them. I washed my hands many, many times and it only came off slowly. I had to resort to a pumice stone to get most of it off.

Maybe other brands of marker wouldn't do this? I don't know.

Just be aware that if you put the ink in strategically poor locations, you're going to get it on your hands and face. It's probably best to avoid the edges in your designs.

Let me know if there are any respirator fashion mods you would like me to test.

Happy drawing!

Update: 19 days later, the ink *still* has not dried on the Aura! It's significantly less smudgy, but I can still rub it onto a sheet of paper.