You can freely build on How Willis Carrier Invented the Modern Air Conditioner
This patent expired in 1924. Every claim — 0 independent, 0 dependent — is now unenforceable. Anyone can use, reproduce, manufacture, sell, or offer for sale this technology without a license.
Original assignee
Buffalo Forge Co
Patent granted
1906
Expired
1924
Forward citations
19
What this patent covers
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 is now free to use
All 0 claims of US 808897 are in the public domain. Specifically:
The 0 dependent claims add narrowing limitations and are also free.
What is NOT covered
Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.
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.
Who is building on this today
The Carrier Corporation remains a global leader in HVAC technology, continuing to refine the principles of thermal management established by this patent. Major competitors like Trane and Daikin also operate within the technical lineage of this foundational work.
Products built on expired version of this technology
Industrial textile mill climate control
Early 20th-century printing press humidity regulation
Commercial HVAC systems
How to cite this patent in your documentation
Buffalo Forge Co. US Patent 808897. Apparatus for treating air.. Granted 1906, expired 1924. Now in the public domain.
Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.
PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.