How to build a PAPRa Mask (v3)

How-To guide for building the Tetra PAPRa mask (Late January 2021 version).

Quick Synopsis

The Tetra Powered Air Purified Respirator requires a Mask component to deliver purified air to the face of the wearer. This mask will be connected to the Fan Box via a CPAP hose. In our testing of the mask, it has been comfortable to wear for several hours, and provides protection while the device is powered on. When the device is powered off, the mask is not effective, and so we are still iterating on the mask design to provide protection when the device is powered off. A single battery charge can provide up to 4 hours of protection, which is sufficient for many use cases for us to feel comfortable publishing this mask.

Parts Required

This photo shows all the parts laid out for building this component:

IMG 5115 L

The assembly diagram can be found here:

Bill of Materials

You will need these components. Prices fluctuate, and so are not included here. Alternative versions can be sourced, and we welcome edits for tested alternatives.

Table 3. Table Bill Of Materials (BOM)
CountDescriptionURLNumber in Package

1

3-ply Medical Face Mask

https://www.cvs.com/shop/cvs-medical-face-mask-soft-ear-loops-50-ct-prodid-2840090

50

1

CPAP Hose (possible candidate-- this product is 3 feet, you may want something longer or shorter)

https://www.amazon.com/Gray-Standard-CPAP-Tubing-foot/dp/B073GBQN73

200 yards

(Length depends on head size and wearing preferences)

Bathing Suit Elastic

https://www.amazon.com/Elastic-Shed-Protector-Handmade-Stretch/dp/B088DB6JQ8

Recommeded Tools

These tools are recommended. URLs are for tools purchased and used in the building of the prototypes:

Table 4. Table Tool List
DescriptionURL

Nail Scissors

https://www.cvs.com/shop/beauty-360-nail-scissors-prodid-328424

Build Steps

Once the mask has been printed, the build consists mainly of getting the 3-ply Medical Face Mask material onto the mask so that the wearer’s exhalations can exit the mask without affecting those around them.

Cut the side supports of the surgical mask off so the accordion folds can be unfolded:

MMR0577 L

Draw a circle on the mask where you want to cut out the filter material (You might be able to get two filters from one mask):

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Cut out the filter material:

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Place the circular gasket into the cap:

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Place the filter material over the gasket and cap:

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Fold the mask so you can place the Mount over the nose portion of the mask:

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Seat the mask over the filter material in the cap:

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Clip all of the clips to hold the filter in place:

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Cut a hole in the bottom of the mask for the grommet (note-- if you just want a passive respirator, no need to do this step!):

IMG 5117 L

Force the grommet through the hole, taking care to rotate the grommet so airflow goes away from the face:

IMG 5118 L
IMG 5119 L

Push the bathing suit elastic through the attachment points on the mask as one long strand. Some prefer to tie at the top of the head, while others may prefer behind the neck. Note how the elastic emerges from behind the attachment points to wrap around the head and neck:

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Congratulations! You now have a TETRA PAPRa face mask v3!

How frequently should I change the filter?

Changing the filter depends on how much you use the device. If you’re using the device where there are a lot of particulates in the air (such as a construction site or a woodshop), you may want to change every few days or so. If you’re using the device where there are less particulates, every two to three weeks should be fine. If the filter material gets dirty or wet, you should change it. The blue layer is intended to be water proof, but we don’t know how much actual water it can take.