How surgical masks are made
The filter layer of a surgical mask often carries a static charge that tugs passing particles onto its fibers.
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- things upstream
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- raw sources
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- steps from the ground
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The short version
A surgical mask is a sandwich of polypropylene nonwovens. The middle filter is melt-blown: molten plastic is squeezed through tiny holes and stretched by hot air into ultrafine fibers. Sturdier spunbond layers go on each side, with a colored water-repellent one facing out. Machines fold in pleats, seal the edges with ultrasonic vibration, add a bendable nose strip and attach elastic ear loops.
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Spin the outer fabric
Molten polypropylene is spun into filaments that fall straight onto a moving belt as a loose web. Heated, patterned rollers then bond the web into spunbond fabric. The outward layer is colored and made water-repellent, and the inner layer stays white and absorbent.
Goes in -
Blow the filter fibers
Melted polypropylene is forced through a die with up to 40 holes per inch while jets of hot air blast the streams. The air stretches them into fibers far finer than spunbond, which tangle on a belt into a soft, weak sheet that traps tiny particles. The fibers are often given a lasting static charge, which helps catch particles that would otherwise slip past.
up to 40 holes per inch
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Stack the three layers
Rolls of outer spunbond, melt-blown filter and inner spunbond unwind together into one three-ply web. The colored side faces the world and the white side faces the wearer.
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Fold in the pleats
Guides fold the web into pleats running across the mask. Unfolded, they let the mask stretch from the bridge of the nose to below the chin.
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Seal the edges ultrasonically
A horn vibrating at ultrasonic frequency presses on the edges and melts the plastic layers together without thread or glue. It adds no contamination, which matters for medical goods.
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Add nose strip and loops
A small bendable metal strip is sealed along the top edge so the mask can be pinched to the nose. Elastic ear loops or tie straps are welded to the four corners.
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Test the filtering
Sample masks face a spray of particles carrying bacteria, about 3 micrometers across. Under the European Type II standard the material must cut the bacteria that get through by at least 98%.
at least 98% bacterial filtration
Worth repeating
- China made 40% of the world's nonwoven fabric as of 2018, most of it in Hebei province.
- During the COVID-19 pandemic, melt-blown fabric jumped from a few thousand US dollars a ton to roughly US$100 thousand a ton.
- Surgical masks came into use in the 1960s and largely replaced cloth masks in developed countries.
Back to the ground
Follow every input upstream and surgical mask starts as these 3 raw sources.
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Sources
Cite this page: "How surgical masks are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/surgical-mask