Particle-filtering half masks (FFP masks) are items of personal protective equipment (PPE) in the context of occupational safety and are intended to protect the wearer of the mask from particles, droplets and aerosols. The design of the particle filtering half masks is different. There are masks without an exhalation valve and masks with an exhalation valve. Masks without a valve filter both the inhaled air and the exhaled air and therefore offer both self-protection and external protection, although they are primarily designed for self-protection. Masks with a valve only filter the inhaled air and therefore do not offer any external protection.