Cleanrooms are controlled environments with minimal airborne particles, essential for semiconductor manufacturing. Why needed: Particles on wafers cause defects. Modern chips have features smaller than particles - even one dust speck ruins circuitry. Contamination sources: People (skin cells, hair), equipment, materials, outside air. Humans are biggest source. Cleanroom features: Filtered air (HEPA/ULPA), positive pressure, controlled temperature/humidity, special flooring, monitored particle counts. Gowning: Full bunny suits, gloves, face masks, shoe covers required. Strict protocols for entry/exit. Airflow: Laminar flow from ceiling to floor. Air changes 300-600 times per hour. Particles swept away. Monitoring: Continuous particle counting, environmental sensors, regular validation. Cost: Very expensive to build and operate. Significant portion of fab construction cost. Cleanroom classes: Class 1, 10, 100 etc. based on particles per cubic foot. Leading fabs use Class 1. Beyond semiconductors: Also used for pharmaceuticals, biotech, optics, aerospace. Maintenance: Filter replacement, regular cleaning with special materials, protocol enforcement.