BUTMASK–H2 half mask against COVID-19

A team of Brno University of Technology researchers and students have developed a 3D printable protection half mask that does not require a special printer or material. The product is intended as improvised personal protective equipment for non-professional use by the general public and can be easily manufactured on regular 3D equipment utilizing the FDM technology (thermoplastic modeling). Although 3D print-outs are usually difficult to seal due to their porosity, the BUT team’s concept has eliminated this problem, allowing the use of standard devices.

NEW: Immediately after the release of the new version of the BUTMASK-H2 we received several requests to increase the filter area. We decided to fulfill this request, consequently a new version designated BUTMASK-H2.1 is released. The updated design provides filter area which is 50 percent larger (approx. 73 cm ^ 2). Attention! Unfortunately, not only a new filter cover needs to be printed, it is necessary to make both parts of the mask again. The assembly procedure remains the same. Of course, the original BUTMASK-H2 files will remain available for download. For more information please see the Download section.

Innovated Model: BUTMASK–H2

Utilizing the feedback provided by the printers‘ community and expert opinions of the initial version, we designed the BUTMask-H2, a substantially revised product with the following features:

• Markedly improved structural layout: The original model appeared to be very uncomfortable if the size had not matched sufficiently; thus, we modified the shape of the product to better distribute the pressure on the face and to reduce the discomfort in, above all, the nasal area.
• More sizes available: As custom-made hard plastic parts will never deliver the relaxed feeling and face adaptability of commercial soft plastic components, the utility value of our half mask closely relates to finding the right size. To satisfy the widest set of users, we designed more size variants than offered in commercially marketed products.

• Children’s options: For children and adults alike, the conveniently trimmed XS and XXS sizes are at hand. The half mask is not to be provided to minors who, if unassisted, cannot put it freely on or off the face in problematic situations. A child wearing the mask must not be left unattended, requiring continuous communication with an adult.
• Less air leaks when on the face: Importantly, the efforts to optimize the product’s shape not only increased the user comfort but also reduced the air leakage, meaning that where already the H1 version yielded very good measurement results, the improved model exhibits superior tightness.
• Modified filter housing: The preliminary tests showed that an original, good quality vacuum cleaner bag can function as a suitable improvised filtering medium. To facilitate smooth performance of the filter, we adjusted its housing compartment and the locking members, thus decreasing spurious pressure on the bag’s active surface.
• An innovated set of headstraps: A close fit on the face is ensured only when the straps have been attached to the head reliably. The attachment options satisfy various user preferences (parallel paths; straps crossed at the back or on the sides of the head; and other custom techniques).

• Indirect venting through lamellae: Recommended by the users! The filter is partly protected by lamellae preventing diverse particles and droplets from impinging directly on the filter’s front section.

If you consider the first model uncomfortable, do not hesitate to try on the new version.

We thank the hundreds of customers who provided their comments and reviews, enabling us to improve the product gradually. The development involved creating dozens of preliminary versions, and many user recommendations were suitably implemented.

Laboratory Testing and Technical Perspectives

The tests performed on BUTMASK-H1 and BUTMASK-H2 confirmed that:

• The sealing properties of a well-fitting half mask fully comply with many of the requirements defined within the EN140 standard.
• Already the first version was designed with favorable effective inner volume, meaning rather small dead space. Although the amount of air exhaled by a normally breathing person is not large, the inner volume of the mask still embodies a major parameter. Our mask keeps its inside tight, letting almost all of the exhaled air out: the user breathes in only a minimum of the exhaled CO2. In this respect, the product is capable of satisfying both the gas mask standards and the markedly stricter medical equipment regulations.
• We believe that the innovated mask, if combined with a regular professional medium for P2 filters, may ensure a sealing rate that conforms to FFP2.
• Our team do not aim to meet FFP3 specifications with a commercial P3 filter, as such items are not commonly retailed or remain in short supply. But we think the improved half mask may succeed in reaching the FFP2 protection level even with an improvised filtering medium, and the tests have shown that the goal is perfectly real.

After the testing, the innovated shape of the frame can be considered final; we will now focus on searching for reliable solutions and paths to take us closer to FFP2.

Conditions of Use

The mask 3D Model Files are distributed under Creative Commons licence of type BY-NC-ND.

The 3D Model Files are available for wholly or partly non-commercial purposes. Please contact us before printing the half mask in larger quantities to be commercially distributed (sold): Even though our vision is to spread the mask widely, some of the recent experiences convinced us that, unfortunately, events just cannot be left to run their course freely. Please note that the BUTMASK-H2 is an improvised protective device and large-scale production in advance of testing and formal approval(s) is not recommended.

Obviously, printing out a couple of dozens (meaning markedly less than 100 pcs) of Butmasks and selling them at prices approximately covering your costs will not be regarded as a business project.

News

7/4/2020

• Improved versions have been tested and are user-ready now. The half masks wear and fit better, do not hurt the face, and allow you to talk. Smaller sizes are available to suit older children.
• A new website trim is being produced, and we are busy writing manuals for different models and designing related documents.
• The PRO mask variant, characterized by a larger filter area, is being developed.

3/4/2020

• A convenient alternative filtering method appears to consist in using vacuum cleaner bags, whose good applicability was confirmed by laboratory tests and real experience (see also https://www.rouskystulkou.org/filtry-do-rousek).
• We will welcome any user info concerning problems and difficulties with the product.

2/4/2020

• A new e-mail address (vutmaska@gmail.com) is available for questions about the half mask.
• The first wide-scale testing cycle is underway, with multiple volunteers printing the mask out. We thank all of these people for their interest and involvement and would also like to ask them to share their experience with the product’s functionality as well as face fitting abilities.
• The user comments are being recorded and responded to, and we are gradually improving the design to offer new models for download. In the "Fabrication Documents" section, the individual model release days are specified.
• Filtering material effectivity testing in progress! Only normally retailed items are included, and we will show the results in installments.