In Buffalo, New York, on July 17, 1902, in response to an air quality problem experienced at the Sackett-Wilhelms Lithographing & Publishing Company of Brooklyn, Willis Carrier submitted drawings for what became recognized as the world's first modern air conditioning system.
The 1902 installation marked the birth of air conditioning because of the addition of humidity control, which led to the recognition by authorities in the field that A/C must perform four basic functions:
control temperature
control humidity
control air circulation and ventilation
cleanse the air
After several more years of refinement and field testing, on January 2, 1906, Carrier was granted U.S. Patent 808,897 for an Apparatus for Treating Air, the world's first spray-type air conditioning equipment.
It was designed to humidify or dehumidify air, heating water for the first function and cooling it for the second.

In 1906 Carrier discovered that "constant dew-point depression provided practically constant relative humidity," which later became known among air conditioning engineers as the "law of constant dew-point depression."
On this discovery he based the design of an automatic control system, for which he filed a patent claim on May 17, 1907.
U.S. Patent 1,085,971 was issued on February 3, 1914.

On December 3, 1911, Carrier presented what is perhaps the most significant document ever prepared on air conditioning –
Rational Psychrometric Formulae – at the annual meeting of the American Society of Mechanical Engineers.
It became known as the "Magna Carta of Psychrometrics."
This document tied together the concepts of relative humidity, absolute humidity, and dew-point temperature, thus making it possible to design air-conditioning systems to precisely fit the requirements at hand.

With the onset of World War I in late 1914, the Buffalo Forge Company, where Carrier had been employed for 12 years, decided to confine its activities entirely to manufacturing.
The result was that seven young engineers pooled together their life savings of $32,600 to form the Carrier Engineering Corporation in New York on June 26, 1915.
The seven were Carrier, J. Irvine Lyle, Edward T. Murphy, L. Logan Lewis, Ernest T. Lyle, Frank Sanna, Alfred E. Stacey, Jr., and Edmund P. Heckel.
The company eventually settled on Frelinghuysen Avenue in Newark, New Jersey.
In Buffalo, New York, on July 17, 1902, in response to an air quality problem experienced at the Sackett-Wilhelms Lithographing & Publishing Company of Brooklyn, Willis Carrier submitted drawings for what became recognized as the world's first modern air conditioning system. The 1902 installation marked the birth of air conditioning because of the addition of humidity control, which led to the recognition by authorities in the field that A/C must perform four basic functions:
control temperature
control humidity
control air circulation and ventilation
cleanse the air
After several more years of refinement and field testing, on January 2, 1906, Carrier was granted U.S. Patent 808,897 for an Apparatus for Treating Air, the world's first spray-type air conditioning equipment. It was designed to humidify or dehumidify air, heating water for the first function and cooling it for the second.
In 1906 Carrier discovered that "constant dew-point depression provided practically constant relative humidity," which later became known among air conditioning engineers as the "law of constant dew-point depression." On this discovery he based the design of an automatic control system, for which he filed a patent claim on May 17, 1907. U.S. Patent 1,085,971 was issued on February 3, 1914.
On December 3, 1911, Carrier presented what is perhaps the most significant document ever prepared on air conditioning –
Rational Psychrometric Formulae – at the annual meeting of the American Society of Mechanical Engineers. It became known as the "Magna Carta of Psychrometrics." This document tied together the concepts of relative humidity, absolute humidity, and dew-point temperature, thus making it possible to design air-conditioning systems to precisely fit the requirements at hand.
With the onset of World War I in late 1914, the Buffalo Forge Company, where Carrier had been employed for 12 years, decided to confine its activities entirely to manufacturing. The result was that seven young engineers pooled together their life savings of $32,600 to form the Carrier Engineering Corporation in New York on June 26, 1915. The seven were Carrier, J. Irvine Lyle, Edward T. Murphy, L. Logan Lewis, Ernest T. Lyle, Frank Sanna, Alfred E. Stacey, Jr., and Edmund P. Heckel. The company eventually settled on Frelinghuysen Avenue in Newark, New Jersey.
Willis Carrier