Selection of raw materials/fabrics

The selection of raw materials can be performed based on the filtration efficiency and hydrophobic capabilities.

Filtration Efficiency and Pressure Drop Across Materials Tested with Aerosols of Bacillus Atrophaeus and Bacteriophage MS2

We read different papers (such as Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?) and we provide a table of the most efficient fabrics based on their filtering capabilities. The table might be updated based on new references or scientific papers. If you want to reuse fabrics from old clothes, check the composition and take by priority fabrics listed higher in the table below. A lot of face mask design allows to have different layers of fabric.

Priority	Fabric type	Reason
1	Non-recycled polyester fabrics	Hydrophobic
2	Recycled polyester fabrics	Hydrophobic (fiber less compact than virgin polyester)
3	Mixed/blend cotton - Poly Cotton	Partially hydrophobic
4	Acetate - 100%	Some good filtering capabilities but depending of the fabric quality
5	100% cotton	Cheap and accessible but less efficient than the above listed
10	Silk	Not recommended (too thin at fiber level) but still better than nothing

Selection of additional filters

In some of the mask designs, an internal enclosure is available to add a complementary filter. Be careful about the materials of the filters which are often design for industrial filtering and not face mask filtering. Some might cause allergy or include some hazardous chemical components.

Filter type	Comments
HEPA filters	Be careful on the MPR (microparticle performance rating) and MERV (minimum efficiency reporting value). 3000 MPR with multiple layers is satisfactory. We do not recommend the use of HEPA filters which are often design for industrial usage only.
Coffee filters	Alone the coffee filters are not sufficient (usually filtering around 25%) but complementary with other fabrics. Another aspect the ability to keep humidity away from the other fabrics.
Felt	Felt has some good breathing capabilities but be careful to select the adequate one. Felt can be made out of synthetic fabrics or natural fabrics such as wool.

Norms

There are different norms and standards for face masks. The norms are listed for references.

Norm	Comment
BSEN14683-2019
GB-19083-2010
GB-T-32610-2016

Mianmö project

Mianmö project is an open source project to allow everyone to build and assemble cloth face masks. The project name is based on the Chinese word 面膜 which means facial mask and a minor IKEAization of the word.

selection-of-fabrics