COVID-19 Designs

A compilation of models being used for treating and preventing the spread of COVID-19

In the past weeks, Fossa Systems has been aiding in the development new 3D printable designs using  to help fight against the severe COVID-19 outbreak near our headquarters in Madrid, Spain.

This page is a catalog of community created and Fossa Systems created components such as valves connectors, adapters that can be used to treat COVID-19 via the use of modified Decathlon Snorkel Respiratory Masks and a series of components. Original Decathlon conversion idea by IsiInnova.

All components are published under a AGPL v3 License and are Open Source for free use and distribution. Do not hesitate to contact us if you need help with the use of the components, need a specific piece designed or have suggestions. All files available on the Ma-D-kers community Gitlab.

DISCLAIMER: These designs are NOT approved by any competent agency or government for sanitary use and are being used under controlled medical supervision authorized by the patient being treated. Please only consider these parts a last resort to saving lives, as is the situation currently in Madrid, Spain. FOSSA Systems or any creators are not responsible for the use or manufacturing of these parts in any way or form.

Decathlon Adapters, Valves and Connectors

Standard Model with no valves or T (Dave connector), T Connector (Dave), T Connector (Dave) with one-way valve and one-way valve


Charlotte V3.2 Valve currently being used for Oxygen treatment, it adapts the Decathlon Easybreath mask to have an input and output. Remove the two interior valve membranes and close the front valve to avoid unfiltered exhalation. There are various configurations possible for use with this part.


Dave T Connector

The “Dave” T connector has been redesigned for a variety of configurations depending on the equipment available and desired configuration. It always features a straight 22M (Oxygen line in) to 22F (Charlotte line in) Connector and can have a 22F or 22M side connector for either an extra Oxygen line or a reservoir bag.  This model Dave has a dual perimeter on the top to directly insert the 15M oxygen plug. Print vertically with support only on bed for the side connector.

There is an In-line One-way valve model for both the 22M and 22F connector which is highly recommended to avoid patient exhalation from going up the O2 line. If the inline model is not used, we recommend printing the external valve. The printed valve uses the two one-way valve membranes which need to be removed from the interior of the decathlon mask.


One-Way Valve

A one way valve is preferable to avoid exhaled air from going up the O2 line to the patient. This one way valve reuses the membranes you need to remove from the interior of the mask. See the Dave section for an integrated version in the connector itself to avoid printing various parts. The valve must go before the reservoir bag if one is used. Currently Male to Female.

For testing an M2 Bolt with a round section of plastic such as a zip-lock bag works instead of the integrated membrane.


PEEP and APL Valves


APL and PEEP valves are used on the expiratory side of the mask to avoid collapsing the lung, PEEP valves are usually not used for the decathlon mask but we have designed a model due to the demand from hospitals. Tested from 2 to 10 cmH2O using BMP280. We will shortly be uploading the APL Valve.

Use a nitrile glove as a seal on the disc.


Mask Configurations


Inlet tract: 1 Oxygen entry (No dave) + One-way valve

Outlet tract: HME Filter + APL/PEEP Valve


Inlet tract: 1 Oxygen entry + Dave with One-way Valve + Reservoir Bag

Outlet tract: HME Filter + APL/PEEP Valve


Inlet tract: 1 Oxygen entry + Dave with One-way Valve + Additional Oxygen Entry

Outlet tract: HME Filter + APL/PEEP Valve


Materials & Recommended Printing Configuration


Use a hot air gun or similar to completely clean the interior of any dust or hairs, this step is imperative and will guarantee that no “junk” can enter the respiratory tract of the patient.

Desinfecting of parts has been tested using paracetic acid, and ultrasound with enzymatic soap.

Printer Settings:

  • Filament: PLA 1.75mm
  • Layer Height: 0.2mm
  • Wall Thickness: 1.6mm
  • Infill: 80%
  • Supports: Only needed for Dave T connector on bed only


Only the following materials have been tested or are confirmed:

  • PA12 / Polymide Filament
  • Orthodontic or medical Resin
  • PLA Filament

Do NOT use standard SLA printer resin as this more toxic than PLA even after being cured.

IMPORTANT!! Printer Calibration:

If this step is not completed the part could not fit in the mask. Print THIS PART  here for calibration

Once printed, fit the cylinder inside the ring, it is necessary for the cynilder to completely pass through the ring with some pressure.

If the ring does not fit it is necessary to modify the horizontal expansion value (Usually between 0.2 and -0.2).

  • If the ring does not fit we need to reduce the value
  • If the ring fits with too much space we need to increase the value.
Blog | Shop

All rights reserved FOSSA Systems © 2018-2020