Fit & Sanitization

Fit & Sanitization FAQ

Q. How do I know if the mask fits correctly?

A. The current BE Mask comes in 3 sizes; S, M, and L.  The sizes we have chosen are based on research and testing of common face geometries.  On this page, we have included specific measurements and a Printable Fitting Guide to help you find the best fit (see below).  If you need to modify the shape and fit for unique individuals, the STL files can be scaled in relation to the X, Y, and Z dimensions using your 3D printer’s slicing software.  For your mask to work correctly, it is important to form a seal around the edge of the mask when the mask is worn.  Fit can be informally tested by holding your hand over the filter before a strong inhalation.  You should feel a suction fit.  Our team is currently developing video guides, tests, printable resources, and local fitting stations in Buffalo, NY to support users make the adjustments they need to be comfortable and safe.  If you are not confident about the fit of your mask, please share your experiences on the BE Hub space for feedback from experts.

Q. How do I properly put on and take off the mask?

A. The CDC offers general guides for best practices of using PPE, including how to put on and take off equipment safely.  Please follow the protocol of your local hospital or organization’s procedures.  Please follow your local government’s guidelines for sanitization to avoid cross-contamination (example: WHO 2014).  

Q. How often should I clean the mask?

A. While masks should be disinfected on a regular basis following accepted sanitization procedures, the frequency depends on use and context. Please review our Cleaning Sources below.

Q. How often should I change the filter?

Filter inserts should be replaced on a regular basis, depending on use and context.  We do not have a recommendation on filter replacement. Please review our Cleaning Sources below.

Q. What is the lifetime of the mask?

A. Our team is currently testing the mask materials to learn about the recommended lifetime of the mask.  We have performed our Sanitization Degredation testing on our materials and continue to research best practices for maintenance.  If you notice any problems, please tell us about them on the BE Hub space.

The BE mask is offered to the general public for general, non-medical purposes. In accord with FDA Emergency Use Authorization, it has been submitted for review to NIOSH. The safety and efficacy of any mask depends on fitting, sanitization practices, and filter materials. Any mask should be tested and fit to meet local needs and standards. Please see our user liability disclaimer for details.


Measure the distance between the bridge of your nose at the level of your eyes and the edge of your chin. Pick the size that is closest to your measurement.

Mask should fit snugly, without gaps around the edge.  

A mask is only fully effective with the correct fit.

MASK SIZES (Chin to Nose):
L:   130 mm (~5 1/8 in)
M:  120 mm (~4 3/4 in)
S:   112 mm (~4 3/8 in)

Mask Sizes


Filter Cartridge Sizes


To use this printable measurement guide, right-click on the image below and click “Save As” to save it to your computer. Then print that image at 100% scale (do not scale it to fit the page). This should result in a properly scaled measurement guide. To be sure, measure the printout to verify that the total width (from one dotted line to the other) measured 6.5 inches (165mm).

Cut on dotted lines and use to measure user face for sizing. Dispose after each use.

Cleaning Sources

Given the severity of the pandemic, sanitation procedures for a reusable mask are of the utmost importance. The World Health Organization’s guidelines for cleaning medical equipment can be found here:

The Montana Mask team is also working on a guide for healthcare workers:

We are currently medically testing a process with our partners. Please stay tuned.