Fit testing kit - guide

The fit test works like this:

  1. Put on your mask.
  2. Stick your tongue out a bit and breathe through your mouth.
  3. Pretend you're doing things you'd normally be doing when wearing your mask.
  4. If you taste bitter, there's a leak!

There's more to it than that so read on, but that's the basic idea.

Table of Contents

Opening the kit

Opening the fit test hood

When you take the fit testing hood out of the box it will be folded up like this:

Gently unfold the hood into a box-like shape, being careful to avoid disturbing the plastic too much. Gently insert your hand into the hood and press against the back of the hood and/or against the sides to sort of prop it open:

It's okay if some of the plastic comes up off from the hood — it doesn't need to be air tight. While not actively using the hood you can place it upside-down, like this:

How to use the nebulizer ('mister')

First time

The transparent part of the nebulizer is where liquid goes (the tank). You can unscrew the tank by gently turning it counter-clockwise until you feel it release. Be gentle!

We check each nebulizer to make sure it's working properly before shipment, but during shipment things might get knocked around. The first time you take the nebulizer out of the box, take the tank off of the base. There is a rubber band that goes inside of the base:

Look around the side of the unit to make sure the band is lying mostly straight and isn't twisted or popping up in any spots. Here's an example of a messed up band:

If the band looks straight then you should be good to go. If the band is popping up or is twisted, see troubleshooting nebulizer issues.

Using the nebulizer

Basic instructions for using the nebulizer are on the box. To screw the tank into the base, gently line up the upper ridge (looks like a tree branch) with the bottom ridge (looks like a foot):

Be careful to not over-tighten or you may strip the plastic.

Performing a mask fit test

Before you begin

Make sure your face is clean shaven if you have facial hair. Your mask will not fit you as well if you have any facial hair (even stubble), so you will likely fail the fit test unless you are clean shaven.

Don't eat / drink anything (besides water), smoke or chew gum for about 15 minutes before the test. If you normally wear glasses, wear glasses during the test.

For best results, you will need some distilled white vinegar. If you don't have distilled white vinegar then distilled water will work. This isn't a strict requirement but it will help your nebulizer last longer. Distilled white vinegar can be found at almost all grocery stores. You will only need a little bit of it.

Setup: the hood

First you'll want to unfold the fit testing hood carefully into a box shape, as described earlier.

Then you'll want to place it over your head, with the sides resting on your shoulders. Like this:

Try to adjust the position of the hood so there aren't major gaps between your body and the hood. If you notice a large gap in the front of the hood, try moving the hood forward so more of it lays on your chest. You can also roll up / fold the paper edges of the hood to get a better fit for your body shape.

The hood doesn't need to be air tight. If you have long / large-volumed hair you will want to pull it back if possible. If you have a jacket / hoodie on, you'll want to take that off.

If the hood does not work for you for some reason (e.g. hair style incompatibility), you can try the alternative testing methods.

Sensitivity test

First let's figure out how sensitive you are to the bitter! We use this information to decide how much to spray into the air.

For this test you will not be wearing a mask.

It's easiest to have someone else holding the nebulizer and doing the test on you, but you can do this test yourself.

  1. Pour a small amount of the sensitivity solution into the nebulizer. Don't pour the whole bottle in! You just need a little bit. The sensitivity solution is in this bottle:

  1. Put the hood over your head, as described above. You should not be wearing a mask for this test.

  2. With your tongue sticking slightly out, breathe through your slightly open mouth.

  3. Hold the nebulizer at least 3 inches away from the hole in the center of the hood. Do not hold the nebulizer directly up against the hole:

Then point the circular metal part of the nebulizer toward the hole in the hood. We want the spray that it makes to go through the hole in the hood.

  1. Turn your head to the side, so your mouth/nose/eyes aren't directly facing the hole in the hood.

  2. Very quickly turn on the nebulizer — less than a second! Just a very quick burst.

  3. Remember to breathe through your slightly open mouth with your tongue sticking out a little bit during the test. Do you taste the bitter? Wait up to 10 seconds to see if you can taste it.

    If you tasted it, you're done with sensitivity test! It took you one spray to taste the bitter.

  4. If you didn't taste it and 10 seconds went by, turn your head to the side again and then do another very quick spray — a very quick burst.

  5. Do you taste the bitter? Wait up to 10 seconds to see if you can taste it.

    If you tasted it, you're done with sensitivity test! It took you two sprays to taste the bitter.

  6. If you didn't taste it and 10 seconds went by, turn your head to the side again and then do another very quick spray — a very quick burst.

    If you tasted it, you're done with sensitivity test! It took you three sprays to taste the bitter.

    If you still can't taste the bitter then something may be wrong with your testing setup or you may be one of the very rare individuals who's insensitive to the bitter taste. See our troubleshooting guide.

Here's a video demo of the sensitivity test:

In this test, only one quick spray of was needed to taste the bitter.

Ick!! The bitter tastes awful! Yes it does! You can have one of the included hard chocolate candies:

This will help get the nasty bitter taste out of your mouth! Now some cleanup:

You do the sensitivity test the first time you test yourself or someone else. You don't need to do the sensitivity test each time you test a new mask.

Mask fit test

Make sure you don't have lingering bitter taste in your mouth from the sensitivity test or previous fit tests. Make sure you haven't eaten or had anything flavored to drink in the past ~15 minutes.

First, put the mask you'd like to test on! We want to test the mask as you'd actually be wearing it, so it's best to leave the mask on for about 5 minutes before beginning the test.

It's easiest to have someone else holding the nebulizer and doing the test on you, but you can do this test yourself.

  1. Pour a small amount of the bitter solution into the nebulizer. Don't pour the whole bottle in! You just need a little bit. The bitter solution is in this bottle:

  1. Put the hood over your head, as described above.

  2. With your tongue sticking slightly out, breathe through your slightly open mouth.

  3. Hold the nebulizer at least 3 inches away from the hole in the center of the hood. Do not hold the nebulizer directly up against the hole:

Then point the circular metal part of the nebulizer toward the hole in the hood. We want the spray that it makes to go through the hole in the hood.

  1. Turn your head to the side, so your mouth/nose/eyes aren't directly facing the hole in the hood.

  2. Very quickly turn on the nebulizer — less than a second! Just a very quick burst. If you needed two sprays to taste the bitter in the sensitivity test, instead use two very quick sprays, one after the other. If you needed three sprays to taste it, use three very quick sprays, one after the other.

  3. After the quick spray is done, return your head to a stationary position facing the front of the testing hood.

  4. If at any time you taste the bitter, stop the test — your mask has failed the fit test.

  5. Continue breathing through your slightly open mouth, tongue sticking slightly out. After 30 seconds, turn your head to the side again and do one more quick spray of the nebulizer. If you needed two sprays to taste the bitter in the sensitivity test then do two very quick sprays. If you needed three sprays to taste the bitter in the sensitivity test then do two (yes two) very quick sprays.

    Then turn your head back to a stationary position when the spraying is done.

  6. Wait 30 seconds in this stationary position, breathing through your slightly open mouth with tongue slightly extended.

If you tasted the bitter at any point during the one minute test then stop — your mask has failed the fit test.

Here's a video demo of the first 30 seconds of the fit test. After this, this 30 second portion is repeated:

Next we test different head positions and movements. In each of these positions, repeat steps above, except instead of keeping your head in a stationary position we do something else.

Here's the positions:

When performing each of these position steps turn your head away from the front of the hood during the spray step. Then return your head to whatever position it should be in after the spraying is done. For instance, during the talking position step, turn your head to the side while talking, spray the nebulizer, then return your head back to the regular position and continue talking.

Normal breathing

We just did this above.

Deep breathing

Breathe in and out deeply, forcing lots of air in and out of the mask.

Here's a video demo of the first 30 seconds of the deep breathing test. After this, this 30 second portion is repeated:

Head side to side

Repeatedly turn your head side to side, facing your shoulders. When turning your head, keep it in the turned position for a few seconds to make sure you're breathing in enough to test the mask.

Here's a video demo of the first 30 seconds of the head side to side test. After this, this 30 second portion is repeated:

Head up and down

Repeatedly turn your head so you're facing up, like you're looking at the sky. Then turn your head so you're facing downward, toward your chest. Keep your head in the turned positions for a few seconds each time to make sure you're testing the mask in the position for long enough.

Here's a video demo of the first 30 seconds of the head up and down test. After this, this 30 second portion is repeated:

Talking

While trying your best to kinda keep your mouth slightly open with your tongue exposed, talk! The included "Rainbow passage" sheet is useful for this step.

Read from the passage as you do this talking step. You may need to read the passage more than once during the full 1 minute test.

Here's a video demo of the first 30 seconds of the talking test. After this, this 30 second portion is repeated:

Bending over / jogging in place

Jog slightly in place, bouncing up and down during the test. Alternatively, if you can do so without the fit testing hood falling off of you, lean your torso forward so you're bending over, like you're trying to touch your toes while standing up.

Here's a video demo of the first 30 seconds of the jogging in place test. After this, this 30 second portion is repeated:

Extra positions

Add any extra positions you think would be useful for you. For instance, if you sing in a choir while wearing your mask, adding a step where you sing would be useful.

Normal breathing

Repeat the first step where you're stationary and breathing normally.

Finishing the test

If you completed each of the ~one minute position steps and didn't taste bitter then your mask passed the fit test!

If at any time you tasted bitter then your mask failed the fit test.

You can log your results on the included test results sheet:

Now for cleanup:

If you tasted any bitter during the test (failed test) or after (lingering in air):

If you're out of our included candies, a piece of chocolate or hard candy usually works.

Alternative methods

Using the garbage bag as a fit testing hood

Included with the kit is an extra large, semi-see-through garbage bag with a drawstring. With care, this can be used as an alternative fit testing hood.

We recommend only using the garbage bag as a fit testing hood if you have someone to supervise you during the test. If you don't have someone to supervise you and the regular hood is not working for you, see the "small enclosed space" method below.

To use the garbage bag method:

  1. Ensure you have someone to supervise you during this test. If you live alone, consider having a friend help you while wearing a well-fitting N95 mask — the fit test can be performed outside.
  2. Place the garbage bag over your shoulders — not around your neck / around your head! Work the garbage bag down until it's past your shoulders and pull in the drawstring a little bit. Do not tighten the drawstring so much you cut off air supply - maintain a large opening at the bottom of the bag, but use the draw string to cinch up the bag a little bit.
  3. Put one of your hands inside of the garbage bag. Hold the nebulizer in this hand. Point the nebulizer away from you, pointed toward the inside of the bag. Hold the nebulizer down toward the bottom of the bag. Like this:

  1. Perform the regular sensitivity testing or fit testing steps described above. For this method you do not need to turn your head away when spraying the nebulizer.

Using a small, enclosed space instead of a fit testing hood

If your home has a small, enclosed space such as a closet or small bathroom you may be able to use this space in lieu of a fit testing hood.

  1. Find a small enclosed space.
  2. Point the nebulizer away from you, into the air.
  3. Perform the sensitivity test as described above. But instead of a "very quick spray" of the nebulizer, perform a ~1 second spray of the nebulizer.
  4. After spraying the nebulizer, swing your arms around to mix up the air in the room. Do this for a few seconds after spraying.
  5. Perform the sensitivity and fit testing steps as described above except with this "swing arms around after spraying" step included.

"Challenge mode" test

The standard fit test described above is capable of detecting a leak of around 1% in the mask. For leaks larger than 1%, the standard fit test, in almost all cases will detect such leaks. But what if you want to see if you have a leak even smaller than 1%?

Rather than use a "very quick, less than a second" spray of the nebulizer every 30 seconds, you can instead spray the nebulizer for longer or more often. I.e. you can spray the nebulizer very quickly every ~10 seconds, or spray it for a full second every ~10 seconds. Just make sure you continue to turn your head away during the spray.

This may increase the sensitivity of the fit test. Meaning you will likely be able to detect an even smaller leak in your mask.

We can't say how small of a leak the "challenge mode" test can detect. But sometimes you just really want to challenge a mask that's already passed a regular fit test and see how far you can push it.

In our experience, the challenge mode test can sometimes detect leaks much smaller than 1% — but we don't have much hard data on this yet. So even if you perform a challenge mode test, it's best to consider your masks that pass a fit test as having "no more than 1% leak."

Troubleshooting

Troubleshooting hood issues

If the see-through plastic is coming loose you can use a bit of tape to secure it if it starts bugging you. Note that the fit testing hood doesn't need to be air tight.

Troubleshooting nebulizer issues

Band twisted / popped up

If you notice the band is popping up or is twisted, you can use a toothpick or similar to push it back into place. If the band is twisted, you can run the toothpick along the band, straightening it out. You can also take the band out and re-seat it in the base of the unit, then straighten it out with a toothpick.

What does passing this fit test mean? What does failing mean?

Roughly speaking, passing the fit test means you're very likely getting around 1% or less leakage while wearing your mask — that 99% or more of the air coming into the mask is passing through the mask rather than leaking around the sides of the mask.

What failing the test means is a bit more complicated. It means you can't assume you are getting 1% or less leakage, or that you can't assume 99% of the air you're breathing is passing through the mask.

I fail in every mask I tested, what should I do?

The first thing to do is to make sure you are following the steps as outlined above. I.e. are you completely clean shaven if you have facial hair?

The next thing to do is to try and find different masks that may fit you better. One type of N95 you may want to try is the 3M Aura style N95 because a high % of people pass fit tests in this kind of N95.

You can work to try to improve the fit of your mask in some of these cases. E.g. if you're wearing an earloop mask, explore tightening the earloops with "cord locks" or by tying them. See this reddit comment thread for some suggestions.

You can also try and figure out where and how you are failing the fit test. For instance, you may be able to figure out that you're failing because your mask is leaking under your chin or around your nose. How can you figure this out? One way is to hold the mask really tightly to your face while doing an abbreviated fit test and see if you pass it.

E.g. if you hold the mask really tight against your chin and pass, but you fail when you don't do that then you've identified where the leak is happening. You can use this information to try and find a mask that might fit you better. E.g. if you're failing under the chin you may need a mask that's shorter, vertically.

If you still cannot pass a fit test on any of the masks you test or any masks you find, you may want to look into alternatives to masks such as Powered Air Purifying Respirators (PAPR), though they are extremely expensive, loud and industrial looking. If you don't have this option, you may still be able to get a rough feel for which of your masks fits you the best based on how intensely and how quickly you taste the bitter during your testing. This is not a precise method, however.

I can't taste the bitter during the sensitivity test

We will be offering an alternative type of testing solution (saccharine) in the future for this situation.

Miscellaneous tips

Where is the link to the fit test kit store?

The fit test kit store can be found at fittests4all.bigcartel.com.