answers: 1950s
context: 1902 Periscope (collapsible) 1902 Mercury arc valve 1902 Air conditioning Air conditioning is the cooling and de-humidification of indoor air for thermal comfort. Using a system of coils as a solution to cool and remove moisture from muggy air in a printing plant that was wrinkling magazine pages, Willis Carrier invented and manufactured the world's first mechanical air conditioning unit in 1902. Carrier's invention – encompassing the first system to provide man-made control over temperature, humidity, ventilation and air quality, was first installed as a solution to the quality problems experienced at a Brooklyn printing plant, Sackett-Wilhelms Lithographing and Publishing </s> the century. The English writer Hugh Plat proposed a steam-based central heating system for a greenhouse in 1594, although this was an isolated occurrence and was not followed up until the 18th century. Colonel Coke devised a system of pipes that would carry steam around the house from a central boiler, but it was James Watt the Scottish inventor who was the first to build a working system in his house. A central boiler supplied high-pressure steam that then distributed the heat within the building through a system of pipes embedded in the columns. He implemented the system on a </s> pass through the house, with an octagonal cupola at the top of the house drawing hot air up and out through natural convection. Whole house fans were the only method for cooling homes in the early 1900s. Air conditioning was invented by Carrier in 1907 but did not become popular until the 1950s. Whole house fans are still ideal for cooling homes when the air outside is cooler than the air inside. There are four types of whole house fans: Whole-house fan A whole house fan is a type of fan, or exhaust system commonly venting into a building's attic,
question: when was central air conditioning invented for homes