wywiewniki
Wywiewniki (sing. wywiewnik) are ventilation outlets used to exhaust air from indoor spaces to the outside. In building engineering they are part of the ventilation system, complementing nawiewniki (supply vents). Wywiewniki can be located on walls, floors, ceilings, or roofs, and are usually fitted with grilles or louvers to protect against precipitation and pests, and with dampers to regulate airflow. They may be passive, relying on natural stack effect, or mechanical, driven by fans in exhaust ducts. In heating and ventilation design, wywiewniki are paired with nawiewniki to maintain air exchange rates, remove humidity and odors, and improve indoor air quality. In residential and commercial constructions, common types include wall-mounted exhaust vents, roof vents, and bathroom/kitchen exhausts. Some wywiewniki include adjustable dampers, insect screens, and anti-draft features. Maintenance typically involves periodic cleaning to remove dust, checking that dampers open and close properly, and ensuring that external grilles are free of obstructions or snow.
Historically, the term is widely used in Polish-speaking regions; older houses may feature visible metal grilles