# How Willis Carrier Invented the Modern Air Conditioner

> Willis Carrier's 1906 patent for an apparatus to control humidity and temperature, forming the technical foundation for modern air conditioning systems.

- **Patent:** US 808897
- **Original title:** Apparatus for treating air.
- **Owner:** Buffalo Forge Co
- **Granted:** 1906
- **Status:** Public domain (expired)
- **Times cited:** 19
- **Field:** mechanical, energy

## What it does

The apparatus treats air by passing it through a spray of water to control its moisture content and temperature. By adjusting the temperature of the water spray, the system can either cool the air or remove humidity through condensation. This process allows for the precise regulation of the air's dew point, which is the temperature at which water vapor turns into liquid. The device essentially creates a controlled environment by balancing thermal and moisture levels within a stream of air.

## What it does NOT cover

- Does not cover chemical-based air purification or filtration systems.
- Does not cover modern vapor-compression refrigeration cycles using chemical refrigerants.
- Does not cover systems that lack a water-spray-based humidity control mechanism.

## The clever bit

Carrier realized that by controlling the temperature of the water spray, he could precisely dictate the moisture content of the air, effectively decoupling temperature control from humidity control.

## Real-world examples

1. Industrial textile mill climate control
2. Early 20th-century printing press humidity regulation
3. Commercial HVAC systems

## Why it matters

This patent marks the birth of modern climate control. It enabled industries like printing and textiles to operate regardless of weather conditions, and eventually transformed global architecture and human comfort by making indoor environments habitable in extreme heat.

## Frequently asked questions

### What does How Willis Carrier Invented the Modern Air Conditioner cover?

Willis Carrier's 1906 patent for an apparatus to control humidity and temperature, forming the technical foundation for modern air conditioning systems.

### Who owns patent US 808897?

Buffalo Forge Co owns this patent, granted in 1906.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 808897 cited by?

This patent has been cited by 19 later patents that build on its ideas.

### What problem does this patent solve?

This patent marks the birth of modern climate control. It enabled industries like printing and textiles to operate regardless of weather conditions, and eventually transformed global architecture and human comfort by making indoor environments habitable in extreme heat.

### What does this patent NOT cover?

Does not cover chemical-based air purification or filtration systems.

**Full plain-English explainer:** https://patentbrief.org/patent/us/808897/air-conditioning-carrier

**Original patent:** https://patents.google.com/patent/US808897

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


## Related patents

Semantically similar inventions in the PatentBrief corpus:

- [John Gorrie's 1851 Patent for Artificial Ice Production](https://patentbrief.org/patent/us/8080/ice-machine-refrigeration-gorrie) — An 1851 patent by John Gorrie describing a mechanical process to create ice by compressing air and using it to cool water.
- [How Percy Spencer Invented the Microwave Oven](https://patentbrief.org/patent/us/2495429/microwave-oven-cooking) — This 1945 patent describes the process of using concentrated microwave energy to cook food, the fundamental technology behind the modern microwave oven.
- [How Glass Fibers Are Spun for Insulation](https://patentbrief.org/patent/us/2133235/fiberglass-glass-wool-slayter) — A 1933 invention by Games Slayter that describes the process of melting glass and blasting it into fine, flexible fibers to create insulation.
- [How William Coolidge Invented the Modern X-Ray Tube](https://patentbrief.org/patent/us/1203495/coolidge-x-ray-tube) — A 1916 patent by William Coolidge for a high-vacuum X-ray tube that used a heated tungsten filament to control electron flow, replacing older, unreliable gas-filled tubes.
- [How the Wright Brothers Invented Modern Airplane Control](https://patentbrief.org/patent/us/821393/wright-brothers-flying-machine) — The foundational patent for the first successful powered, heavier-than-air flying machine that could be controlled in flight.