Willis Carrier invented the modern air-conditioning system, first demonstrated in 1902 for a Brooklyn printing plant.
Carrier designed the system for Sackett-Wilhelms Lithographing and Publishing Company, where changing humidity caused paper to expand and contract. That variation disrupted color printing. His equipment controlled both temperature and humidity, making the process more reliable.
Carrier’s invention was not the first attempt to cool air, but it was a major step toward modern air conditioning. The system used coils, fans, ducts, and humidity control rather than simply blowing cold air into a room.
People often associate air conditioning only with comfort, but its early industrial uses were especially important. Textile mills, printing plants, theaters, and later homes all benefited from controlled indoor climates. Carrier founded the Carrier Engineering Corporation in 1915.