Coloured scanning electron micrograph (SEM) of a cross-section through an FFP2 (filtering facepiece 2) face mask. FFP is a European standard. FFP2 masks filter at least 94 percent of airborne particles. The outer layers (blue) of this mask are made from two different spunbond fabrics. The five internal layers (white) are made from very fine meltblown fabric. The layers may be electrostatically charged so that particles adhere to them better. Spunbond and meltblown materials are both nonwoven fabrics formed from fibres of thermoplastic resin, typically polypropylene, bonded by heat and or pressure. Magnification: x28 when printed at 15cm wide.