Spirometers are essential medical devices designed to measure lung function through spirometry, a non-invasive test that assesses the volume and speed of air a person can inhale and exhale. By having patients breathe forcefully into a mouthpiece connected to sensors—such as turbines, pistons, or ultrasonic transducers—these tools record key metrics like forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and peak expiratory flow (PEF), producing spirograms with volume-time curves and flow-volume loops. They diagnose and monitor respiratory conditions including asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis, while incentive spirometers encourage deep breathing to prevent post-surgical complications like atelectasis. Available in types like volume-displacement, flow-sensing, and portable digital models, spirometers are vital in clinics, hospitals, and home care for tracking disease progression and treatment efficacy.