Vital capacity (VC) refers to the total amount of air that can be exhaled after a maximum inhalation. Average vital capacity for adult men is approximately 3500-4000 milliliters, while for women it is around 2500-3000 milliliters. Higher vital capacity generally indicates better respiratory health. A spirometer is a portable, handheld device used to measure the volume of air exhaled from the lungs. It provides data that reflects lung function and airway ventilation. The importance of vital capacity: Lung vital capacity is closely related to respiratory function. Low spirometry values compared to normal ranges may indicate reduced oxygen intake and impaired internal oxygen supply. When the body requires increased oxygen—such as during prolonged mental activity, physical work, or exercise—insufficient oxygen delivery may lead to symptoms like headache, dizziness, chest tightness, fatigue, poor concentration, memory issues, or sleep disturbances. These effects can impact daily performance and overall well-being. Usage instructions: 1. Move the red movable marker to the starting point. 2. Place the blue mouthpiece in your mouth, inhale deeply, hold your breath briefly, then exhale forcefully and completely into the device, attempting to move the marker as far as possible. 3. Observe the marker's position on the scale. Average readings for healthy adults are approximately 400 L/min for men and 350 L/min for women, with trained athletes often reaching 600–700 L/min. (Note: This device measures in liters per minute. To convert to milliliters per minute, multiply by 1000. For example, 400 L/min equals 4000 mL/min.) How to use the peak flow meter: Set the red indicator to the bottom of the scale. Ensure fingers do not obstruct the pointer’s movement. Stand upright and take a deep breath. Insert the mouthpiece into your mouth and seal your lips tightly around it. Exhale as forcefully and quickly as possible. Record the value indicated by the red marker, then reset the marker to zero. Repeat the process three times and record the highest reading. Key points: exhale with maximum effort and speed; ensure a tight seal around the mouthpiece to prevent air leaks; do not block the mouthpiece with your tongue. For repeated tests, always reset the red indicator to the lowest point on the scale before each attempt. Package includes: 1 x Spirometer (for adult or child, color may vary)