N95 masks look simple enough: two outer layers of fabric that form the shape of the mask, with a thin filter between.\u00a0It\u0027s that sandwiched inner layer that complicates the mask\u0027s construction and differentiates medical-grade protection from a homemade mask.A surge in demand for material for that layer is a key reason for the global shortage of N95s.The filter is made of thousands of nonwoven fibers, each thinner than a strand of hair and fused together through a process known as melt blown extrusion.\u00a0Manufacturers of the material have been pushed to produce at unprecedented levels, straining an industry that relies on complex machinery and specialized training that\u0027s part technical and part "art form," according to some in the industry."The supply chain has gotten nuts for this particular material," said Nozi Hamidi, vice president of marketing and business development for SWM International, one of roughly two dozen domestic manufacturers of melt blown material. "We experienced this when SARS happened 17 or so years ago, but not to this extent. This is just absolutely insane."When the coronavirus began spreading rapidly in January in China and Taiwan, Chinese manufacturers of melt blown material started getting backlogged with their own domestic orders.Taiwan, which is capable of producing 91 million masks per week, instituted a ban on exports of the material. To put Taiwan\u0027s output into perspective, the United States\u0027 largest mask producer, 3M, can supply 55 million masks per month.The changes to the Chinese and Taiwanese markets "sent ripples through the supply chain," Hamidi said.Around that time, SWM and other American manufacturers began taking steps to increase production capacity. SWM boosted capacity by 250%, by hiring and training new workers and converting its Middletown, Delaware plant so it could run 24 hours a day.\u00a0Even with that increase, Hamidi said the company has had to warn new customers about long waits, and referred some to competitors."We\u0027re trying to not turn away people, but the reality of the situation at least for us is we\u0027re sold out well into 2020, so if we take on a new customer right now, they basically have to wait," Hamidi said. "We have to say to them that it might be until the end of 2020 or into 2021 before we can actually get you going as a new customer."The melt blown material is made on 90-inch-wide conveyor belts, coated in layers of fine white plastic fibers that combined have the consistency of cotton candy. Each thread is simultaneously fed through one of thousands of tiny precision-formed holes. A blast of hot air on the other side fuses fibers together so tightly that while air can pass through the microscopic perforations between them, more than 95% of microbes can\u0027t get through.That is what makes the melt blown layer the most important part of the mask, and the hardest to produce, according to Albert Shih, a University of Michigan biomedical engineering professor."The outer two layers, there are plenty of supplies, but this material is not easy to obtain or make, and you cannot just start a new line. You have to show that the microbes won\u0027t penetrate it and get into the lungs," Shih said.Even established companies are having trouble boosting production because they can\u0027t simply buy more machines, according to Dave Rousse, president of INDA, the Association of the Nonwoven Fabrics Industry."There are only five or six companies across the globe that make these machines, and they\u0027re not inexpensive. These are sizable machines, a lot of technology, a lot of air handling, a lot of electronics, a lot of precision moving parts," Rousse said. "Normally it\u0027s nine to 12 months before you could get a machine delivery."He added that INDA has explored using an antiquated glass fiber material that was used for filtration before melt blown became standard."It\u0027s more brittle and, as you can imagine, not as comfortable. But in a pinch there might be some folks who used to make that who can be called back into action," Rousse said.Rousse said the demand for face masks with melt blown filters is "far higher" than it\u0027s ever been.\u00a0"We\u0027ve had conversations with hospitals and medical unions that won\u0027t feel comfortable until they\u0027ve got stockpiles. And you\u0027ve got many more people feeling the need to comply with the CDC advice to wear a face mask in public. And they say \u0027If I\u0027m going to wear a face mask, I want the best damn face mask money can buy\u0027," Rousse said.That demand can draw away from other uses for melt blown material, including some safety and medical products, according to Brad Kalil, INDA\u0027s Director of Market Intelligence and Economic Insights.\u00a0"Prior to the outbreak, only about a third of the melt blown production was actually going to filtration," Kalil said. "Some of it goes to wipes, some of it to sorbents, which are the absorbent materials for oil booms or shop floors that soak up water and oil. Some of it goes to transportation in the acoustic material of a car, and some of it goes to medical surgical wound care."But the industry has changed as rapidly as American society in the past few weeks. Many in the melt blown industry are among those considered essential and cleared to report to work each day. An engineer for SWM who asked not to be named said, "It\u0027s been a grind, and the grind is not pretty," but said he and his team realize they\u0027re playing a role in a larger struggle."These are uncertain times. We know this is a priority product, and there\u0027s pride in that," the engineer said.