Analogous Prior Art or Not? A critical patent obviousness question


During the examination of a patent application, a USPTO examiner may cite two or more pieces of prior art (e.g., U.S. Patents or U.S. Patent Applications) and take the position that the claimed invention is obvious in light of the cited prior art. Similarly, in a patent litigation context, a defendant may argue that the asserted patent is invalid for  being obvious over one or more pieces of prior art. In order for a prior art document to be relevant to the question of obviousness, the prior art document has to be analogous to the claimed invention. There are two tests to determine if a prior art reference is analogous: 

(1) whether the art is from the same field of endeavor, regardless of the problem addressed and, 

(2) if the reference is not within the field of the inventor’s endeavor, whether the reference still is reasonably pertinent to the particular problemwith which the inventor is involved.

Applying these tests is not easy, and various parties in a dispute can arrive at different conclusions. A good example isAirbus S.A.S. v. Firepass Corporation, a case decided by the United States Court of Appeal for the Federal Circuit recently, on November 8, 2019. 

Summary of the Airbus Case

Airbus S.A.S. has appealed the Patent Trial and Appeal Board’s reversal of the patent examiner’s rejection of certain new claims presented by patent owner Firepass Corporation in an inter partes reexamination of U.S. Patent No. 6,418,752. Airbus challenged the Board’s finding that an asserted prior art reference fails to qualify as relevant prior art because it is not analogous to the claimed invention of the ’752 patent. 

The ’752 patent discloses a fire prevention and suppression system that prevents and extinguishes fires using breathable air instead of water, foam, or toxic chemicals, based on the inventor’s alleged discovery that a low-oxygen (“hypoxic”) but normal pressure (“normbaric”) atmosphere inhibits fire ignition and combustion, yet remains breathable for humans.

The asserted prior art reference at issue on appeal, U.S. Patent No. 5,799,652 (Kotliar), is an earlier-issued patent that discloses equipment for providing hypoxic air in an enclosed area for the purposes of athletic training or therapy. This invention can simulate low-oxygen mountain air for training at different elevations. 

The examiner considered other prior art references as part of Airbus’s validity challenges of the ’752 patent. One is a study focused on “human performance during [a] prolonged stay in normobaric hypoxia, a so-called ‘fire retardant atmosphere.’” Another prior art was a report from the U.S. Navy that examines the medical hazards of four types of flame-suppressant atmospheres for “sealed chambers.” Another prior art explored the effect of “nitrogen-based, fire-retardant atmospheres” on human performance, particularly visual sensitivity. Lastly, another prior art considered was the U.S. Patent No. 3,893,514 (Carhart) titled “Suppres- sion of Fires in Confined Places by Pressurization.” Carhart explains that “[i]t is well known to those skilled in the art that fires are supported by oxygen and that by using some means to deplete the surrounding area of oxygen or lowering the percent of oxygen the fire will be suppressed.”

Examiner’s Position: the claims in question were obvious over Kotliar in view of the other prior art.

PTAB’s Decision: Examiner erred because Kotliar was not analogous art. The Board explained that “[t]here is no articulated rational underpinning that sufficiently links the problem of fire suppression/prevention confronting the inventor” of the ’752 patent to the invention disclosed in Kotliar, “which is directed to human therapy, wellness, and physical training.” In doing so, the Board declined to consider Airbus’s argument that “breathable fire suppressive environments [were] well-known in the art” because none of the four references relied on by Airbus was specifically used to support the examiner’s rejection of claims.

The Federal Circuit Court’s Decision: the Court vacated the Board (PTAB) decision and remanded the case back to the Board for further consideration; the Court held that the Board erred in its analogous art analysis by declining to consider record evidence (i.e., the additional four prior art references mentioned above) relied on by Airbus to demonstrate the knowledge and perspective of a person of ordinary skill in the art at the time of the invention.


Whether a prior art reference is analogous and thus can be used in an obviousness analysis should be considered by all parties involved (e.g., patent applicant, patentee). The grant or the validity of the respective patent may be dependent on the answer to this question.  


See entire Court Decision at


Disclaimer: The views and opinions expressed throughout this blog are the views and opinions of the individual author(s) and/or contributor(s) and do not necessarily reflect the views and opinions of our firm, CIONCA IP Law. P.C

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  • Marin Cionca2/9/2020 7:46:10 PM

    Analogous Prior Art or Not? A critical patent obviousness question

Marin Cionca | Founder of CIONCA IP

Marin Cionca, Esq.

Registered Patent Attorney

USPTO Reg. No. 63899

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