In 1995, Germany made CFC refrigerators illegal.[22] DuPont and other companies blocked the refrigerant in the U.S. with the U.S. EPA, disparaging the approach as "that German technology".[21][23] Nevertheless, in 2004, Greenpeace worked with multinational corporations like Coca-Cola and Unilever, and later Pepsico and others, to create a corporate coalition called Refrigerants Naturally!.[22][24] Then, four years later, Ben & Jerry's of Unilever and General Electric began to take steps to support production and use in the U.S.[25] In 2011 the EPA decided in favor of the ozone- and climate-safe refrigerant for U.S. manufacture.[17][26][27]

In 1902, the first modern electrical air conditioning unit was invented by Willis Carrier in Buffalo, New York.[citation needed] After graduating from Cornell University, Carrier found a job at the Buffalo Forge Company. There, he began experimenting with air conditioning as a way to solve an application problem for the Sackett-Wilhelms Lithographing and Publishing Company in Brooklyn, New York. The first air conditioner, designed and built in Buffalo by Carrier, began working on 17 July 1902.[citation needed]
Next check and clean the furnace’s flame sensor. The video below shows you how—note that this guy fixes it in about 5 minutes. We would probably use a little bit of emory paper, but he cleans the sensor with a 5-dollar bill. Another video further down the page under the discussion of “If your furnace keeps shutting off after about 5 minutes” shows the same project with a different brand of furnace.
For residential homes, some countries set minimum requirements for energy efficiency. In the United States, the efficiency of air conditioners is often (but not always) rated by the seasonal energy efficiency ratio (SEER). The higher the SEER rating, the more energy efficient is the air conditioner. The SEER rating is the BTU of cooling output during its normal annual usage divided by the total electric energy input in watt hours (W·h) during the same period.[33]

Air conditioning makes deep plan buildings feasible, for otherwise they would have to be built narrower or with light wells so that inner spaces received sufficient outdoor air via natural ventilation. Air conditioning also allows buildings to be taller, since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings.[citation needed] Comfort applications are quite different for various building types and may be categorized as:
High-efficiency condensing furnaces (90% AFUE and above) are a bit more complex than conventional furnaces. The main differences between a conventional and condensing furnace are the heat exchanger technology used to extract heat from the combustion process and the method used to exhaust the combustion gases. In these ways, the furnaces are very different. The condensing furnace does not have a significantly more efficient combustion process than does a conventional furnace; both use gas burners with electronic ignition. The difference lies in that the condensing furnace has a more efficient heat extraction process after combustion.