  United States Court of Appeals
      for the Federal Circuit
                ______________________

                    AIRBUS S.A.S.,
                       Appellant

                           v.

             FIREPASS CORPORATION,
                       Appellee
                ______________________

                      2019-1803
                ______________________

    Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. 95/001,555.
                  ______________________

              Decided: November 8, 2019
               ______________________

    MARK ALEXANDER CHAPMAN, Hunton Andrews Kurth
LLP, New York, NY, argued for appellant. Also repre-
sented by CLIFFORD ULRICH.

    ROGER THOMPSON, The Law Offices of Roger S. Thomp-
son, New York, NY, argued for appellee.
                ______________________

   Before LOURIE, MOORE, and STOLL, Circuit Judges.
STOLL, Circuit Judge.
   Airbus S.A.S. appeals the Patent Trial and Appeal
Board’s reversal of the patent examiner’s rejection of
2                                  AIRBUS S.A.S. v. FIREPASS CORP.




certain new claims presented by patent owner Firepass
Corporation in an inter partes reexamination of U.S. Pa-
tent No. 6,418,752. Airbus challenges the Board’s finding
that an asserted prior art reference fails to qualify as rele-
vant prior art because it is not analogous to the claimed
invention of the ’752 patent. We hold that the Board erred
in its analogous art analysis by declining to consider record
evidence 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. We therefore vacate the Board’s
reversal of the examiner’s rejection and remand for recon-
sideration in view of this additional evidence.
                        BACKGROUND
     This inter partes reexamination returns from a prior
appeal in which we vacated the Board’s decision dismissing
Airbus’s cross-appeal for lack of jurisdiction and remanded
to the Board to consider Airbus’s challenge to certain newly
presented claims. See generally Airbus S.A.S. v. Firepass
Corp., 793 F.3d 1376 (Fed. Cir. 2015). Airbus now appeals
the Board’s reversal of the examiner’s rejection of those
newly presented claims on remand.
                               I
    The ’752 patent discloses a fire prevention and sup-
pression system that prevents and extinguishes fires using
breathable air instead of water, foam, or toxic chemicals—
each of which can present risks to personnel or electronic
equipment. See ’752 patent col. 1 ll. 47–65, col. 2 ll. 41–64.
The invention is based on the inventor’s alleged discovery
that a low-oxygen (“hypoxic”) but normal pressure
(“normbaric”) atmosphere inhibits fire ignition and com-
bustion, yet remains breathable for humans. See id.
at col. 4 l. 60–col. 5 l. 25. More specifically, the ’752 patent
explains that, if one reduces the atmospheric concentration
of oxygen from its natural level of 20.94% to about 16.2%
or slightly lower while adding nitrogen to maintain the
same air pressure, fires are suppressed while humans can
AIRBUS S.A.S. v. FIREPASS CORP.                                3



continue to breathe. Id. at col. 6 ll. 21–67. The specifica-
tion applies this principle to various fire-preventative and
fire-suppressive enclosed facilities, from computer rooms
and automobile tunnels to military vehicles and spacecraft.
See id. at col. 10 l. 55–col. 22 l. 45. These enclosed facilities
can utilize a “hypoxic generator” that produces hypoxic air
by altering the composition of the surrounding ambient air.
See id. at col. 9 l. 36–col. 10 l. 21. But “[a]ny oxygen extrac-
tion device, such as a nitrogen generator or an oxygen con-
centrator can be used instead of a hypoxic generator” with
certain adaptations. See id. at col. 10 ll. 22–54.
    Claim 91, the only independent claim at issue on ap-
peal, is illustrative of the claimed invention:
    91. A system for providing breathable fire-preven-
    tive and fire suppressive atmosphere in enclosed
    human-occupied spaces, said system comprising:
    an enclosing structure having an internal environ-
    ment therein containing a gas mixture which is
    lower in oxygen content than air outside said struc-
    ture, and an entry communicating with said inter-
    nal environment;
    an oxygen-extraction device having a filter, an inlet
    taking in an intake gas mixture and first and sec-
    ond outlets, said oxygen-extraction device being a
    nitrogen generator, said first outlet transmitting a
    first gas mixture having a higher oxygen content
    than the intake gas mixture and said second outlet
    transmitting a second gas mixture having a lower
    oxygen content than the intake gas mixture;
    said second outlet communicating with said inter-
    nal environment and transmitting said second mix-
    ture into said internal environment so that said
    second mixture mixes with the atmosphere in said
    internal environment;
4                              AIRBUS S.A.S. v. FIREPASS CORP.




    said first outlet transmitting said first mixture to a
    location where it does not mix with said atmos-
    phere in said internal environment;
    said internal environment selectively communi-
    cating with the outside atmosphere and emitting
    excessive internal gas mixture into the outside at-
    mosphere;
    said intake gas mixture being ambient air taken in
    from the external atmosphere outside said internal
    environment with a reduced humidity; and
    a computer control for regulating the oxygen con-
    tent in said internal environment.
J.A. 77.
                              II
     The asserted prior art reference at issue on appeal,
U.S. Patent No. 5,799,652 (Kotliar), is an earlier-issued pa-
tent with the same named inventor as the ’752 patent. 1 Ko-
tliar discloses equipment for providing hypoxic air in an
enclosed area for the purposes of athletic training or ther-
apy. Kotliar col. 1 ll. 14–29. The disclosed invention can
simulate low-oxygen mountain air for training at different
elevations. See id. at col. 1 ll. 50–53, col. 2 ll. 5–10. The
disclosed system uses a “hypoxicator” that, similar to the
“hypoxic generator” of the ’752 patent, produces hypoxic air
by altering the composition of the surrounding ambient air.
See id. at col. 3 ll. 18–47. The Kotliar specification dis-
closes a preferred oxygen range of 7% to 15%, which is


    1    The ’752 patent expressly acknowledges that its in-
vention is “related in part” to Kotliar—at least in a subject
matter sense. ’752 patent col. 1 ll. 14–15; see also id.
at col. 4 ll. 60–62 (referencing “Hypoxic Room System”
manufactured by Hypoxico Inc., the named assignee of Ko-
tliar).
AIRBUS S.A.S. v. FIREPASS CORP.                              5



below the 16.2% flame-preventative threshold disclosed in
the ’752 patent. See id. at col. 4 ll. 21–24. Kotliar explains
that its system could be applied to “any closed room or
structure,” id. at col. 8 ll. 14–25, and also envisions its ap-
plication to the passenger compartment of an automobile,
see id. at col. 8 l. 34–col. 9 l. 39.
                              III
    Beyond Kotliar, the examiner considered other prior
art references as part of Airbus’s validity challenges to
other claims of the ’752 patent. 2 Four of these references
are relevant on appeal.
    Gustafsson 3 is a study focused on “human performance
during [a] prolonged stay in normobaric hypoxia, a so-
called ‘fire retardant atmosphere.’” J.A. 1860. The refer-
ence explains that “[r]educed oxygen levels have . . . been
discussed for fire prevention in closed spaces, such as sub-
marines, computer rooms, store rooms, archives, or muse-
ums.” Id. It further explains that “if humans are to work
and live in localities where hypoxic atmospheres are used,
a balance must be struck between the level of fire preven-
tion achieved and the effect of hypoxia on human perfor-
mance.” Id. After surveying the literature, Gustafsson
discloses the results of a human performance experiment
in which the subjects were exposed to different levels of
normobaric hypoxia for periods extending up to ten days.




    2   Firepass did not appeal the examiner’s rejection of
these other claims to the Board. Instead, Firepass canceled
claims 29–90 and 95–100 prior to its latest appeal to the
Board.
    3   Christina Gustafsson et al., Effects of Normobaric
Hypoxic Confinement on Visual and Motor Performance,
68 AVIATION, SPACE, & ENVTL. MED. 985 (1997).
6                              AIRBUS S.A.S. v. FIREPASS CORP.




    The 1167 Report 4 is a report from the U.S. Navy that
examines the medical hazards of four types of flame-sup-
pressant atmospheres for “sealed chambers.” J.A. 1872.
One of the disclosed “modifications of air that will suppress
or extinguish flames” is the partial replacement of oxygen
by nitrogen, or “N2 Dilution.” J.A. 1871–72. Another is
“N2 Pressurization,” the addition of compressed nitrogen to
air. Id. After surveying the literature, the 1167 Report
discloses the results of six experiments performed to assess
the effect of hypoxia at normobaric pressure on health and
mental function over time. The 1167 Report endorses the
use of N2 Dilution to suppress flames aboard patrolling
submarines. It further suggests that N2 Dilution and
N2 Pressurization “may be combined at minimal hazard to
the crews serving aboard patrolling submarines.”
J.A. 1871.
    Luria, 5 which shares an author with the 1167 Report,
similarly explores the effect of “nitrogen-based, fire-retard-
ant atmospheres” on human performance, particularly vis-
ual sensitivity. J.A. 2669–70. The reference discloses
various experiments and concludes that the results support
a strategy of reducing oxygen concentration to suppress
fires.
    U.S. Patent No. 3,893,514 (Carhart) is titled “Suppres-
sion of Fires in Confined Places by Pressurization.” Car-
hart 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.”


    4 D.R. KNIGHT, NAVAL SUBMARINE MED. RESEARCH
LAB., REPORT NO. 1167, THE MEDICAL HAZARDS OF FLAME-
SUPPRESSANT ATMOSPHERES (1991).
    5 D.R. Knight et al., Effect of Nitrogen-Based, Fire-Re-

tardant Atmospheres on Visual and Mental Performance,
UNDERWATER AND HYPERBARIC PHYSIOLOGY IX (1987).
AIRBUS S.A.S. v. FIREPASS CORP.                              7



Carhart col. 1 ll. 17–20. Carhart also explains that it is
well-known that “[s]uppression of fires in open spaces and
in confined spaces require[s] different efforts to extinguish
the fire.” Id. at col. 1 ll. 20–22. And, “the presence of ma-
chinery, electrical equipment, and more importantly the
presence of human beings within the area of a fire requires
special considerations for the type of extinguishant used.”
Id. at col. 1 ll. 22–26.
     Carhart is specifically “directed to a system and
method of adding nitrogen under pressure to a confined
area including a habitable atmosphere to suppress a fire
without any deleterious effects on humans within the envi-
ronment in which the fire is suppressed.” Id. at col. 1
ll. 61–65. An object of the disclosed invention is to “sup-
press a fire in a closed chamber while maintaining an en-
vironment suitable for human activity.” Id. at col. 2 ll. 6–
8. The areas of interest include “confined storage areas
such as a room-type safe or machine room that require a
controlled environment,” but Carhart’s system “may be
used for any controlled habitable environment which is ei-
ther an enclosed area or an area which may be closed by
closing of a door or window.” Id. at col. 2 ll. 56–64; see also
id. at col. 4 ll. 27–32 (similar).
                              IV
    On remand from this court, the examiner rejected
newly presented claims 91–94 as obvious over Kotliar in
view of other prior art. The examiner also rejected other
claims as obvious over various combinations of Kotliar with
each of Gustafsson, the 1167 Report, Luria, and Carhart.
Before the examiner, Firepass disputed whether Kotliar
disclosed certain claim limitations and a motivation to
combine the asserted prior art. But Firepass did not dis-
pute Kotliar’s status as analogous art to the ’752 patent.
Accordingly, the examiner evaluated neither Kotliar’s sta-
tus as analogous art, nor the disclosures of Gustafsson, the
1167 Report, Luria, and Carhart as background references
8                              AIRBUS S.A.S. v. FIREPASS CORP.




establishing the knowledge and perspective of a person of
ordinary skill in the art at the time of the invention.
     Firepass appealed the examiner’s rejection of
claims 91–94 to the Board. Firepass then argued for the
first time that Kotliar is not analogous art to the claimed
invention of the ’752 patent, and is therefore not relevant
prior art for the purposes of obviousness. The examiner did
not respond to this new argument in his answer, resting
instead on his prior rejections. For its part, Airbus did not
argue in its respondent brief that Firepass had waived this
new argument; instead, Airbus addressed the issue on the
merits. In relevant part, Airbus relied on Gustafsson, the
1167 Report, Luria, and Carhart to argue that “[i]t was
well-known before the alleged invention of the ’752 patent
that a reduced oxygen atmosphere could be both breath-
able and fire suppressive.” J.A. 4297; see also J.A. 4298–
99.
    The Board found that Kotliar was not analogous art
and reversed the examiner’s rejections of claims 91–94.
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 train-
ing.” J.A. 13. In doing so, the Board declined to consider
Airbus’s argument that “breathable fire suppressive envi-
ronments [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 91–94. Id.
    Airbus appeals the Board’s reversal of the examiner’s
rejection.    We have jurisdiction under 28 U.S.C.
§ 1295(a)(4)(A).
                        DISCUSSION
   On appeal, Airbus challenges the Board’s finding that
the Kotliar reference is not analogous to the claimed
AIRBUS S.A.S. v. FIREPASS CORP.                             9



invention of the ’752 patent. 6 A reference qualifies as prior
art for an obviousness determination only when it is anal-
ogous to the claimed invention. In re Klein, 647 F.3d 1343,
1348 (Fed. Cir. 2011). Whether a reference qualifies as
analogous prior art is a question of fact that we review for
substantial evidence. In re Bigio, 381 F.3d 1320, 1324
(Fed. Cir. 2004).
     Two separate tests define the scope of analogous prior
art: “(1) whether the art is from the same field of endeavor,
regardless of the problem addressed and, (2) if the refer-
ence is not within the field of the inventor’s endeavor,
whether the reference still is reasonably pertinent to the
particular problem with which the inventor is involved.”
Id. at 1325 (first citing In re Deminski, 796 F.2d 436, 442
(Fed. Cir. 1986); then citing In re Wood, 599 F.2d 1032,
1036 (C.C.P.A. 1979)). The Board held that Kotliar does
not qualify as prior art under either of these two tests. For
the reasons that follow, we hold that the Board’s “field of
endeavor” determination is supported by substantial evi-
dence, but the Board erred in its “reasonably pertinent” de-
termination because the Board declined to consider record
evidence advanced by Airbus to demonstrate the
knowledge and perspective of a person of ordinary skill in
the art at the time of the invention.
                                  I
   We first address the Board’s application of the field of
endeavor test. In resolving questions of obviousness, “we



    6   On appeal, Airbus also challenges the Board’s var-
ious determinations regarding waiver, including the
Board’s determination that Firepass did not waive its non-
analogous art argument when it failed to raise that argu-
ment before the examiner. See generally Appellant’s
Br. 59–69. We have considered Airbus’s arguments, but we
find no reversible error in the Board’s waiver analysis.
10                            AIRBUS S.A.S. v. FIREPASS CORP.




presume full knowledge by the inventor of all the prior art
in the field of his endeavor.” Wood, 599 F.2d at 1036. To
determine the applicable field of endeavor, the factfinder
must consider “explanations of the invention’s subject mat-
ter in the patent application, including the embodiments,
function, and structure of the claimed invention.” Bigio,
381 F.3d at 1325 (first citing Wood, 599 F.2d at 1036; then
citing Deminski, 796 F.2d at 442). In Wood, for example,
our predecessor court determined the field of endeavor
based on an express disclosure in the Background of the
Invention section of the applicant’s specification. 599 F.2d
at 1036.
     While the disclosure of the references is the primary
focus, this court has also instructed that the factfinder
must consider each reference’s disclosure in view of the
“the reality of the circumstances,” Bigio, 381 F.3d at 1326
(quoting In re Oetiker, 977 F.2d 1443, 1447 (Fed. Cir.
1992)), and “weigh those circumstances from the vantage
point of the common sense likely to be exerted by one of
ordinary skill in the art in assessing the scope of the en-
deavor,” id. In Deminski, for example, this court found that
the challenged prior art references were in the same field
of endeavor because they disclosed pumps and compressors
that had “essentially the same function and structure” as
the claimed piston devices. 796 F.2d at 442.
    The Board’s finding under the field of endeavor test is
supported by substantial evidence. The Board looked to
the written description and claims of the ’752 patent and
Kotliar to determine the field of endeavor for each refer-
ence. Based on the ’752 patent’s disclosure, the Board
found that the field of endeavor for the ’752 patent is “de-
vices and methods for fire prevention/suppression.” J.A. 8.
For support, the Board relied on the preamble of claim 1 of
the ’752 patent, which recites “[a] system for providing
breathable fire-preventive and fire suppressive atmos-
phere in enclosed human-occupied spaces.” Id. (emphasis
AIRBUS S.A.S. v. FIREPASS CORP.                           11



omitted) (quoting ’752 patent col. 22 ll. 48–50). 7 The Board
also cited the title of the ’752 patent, which similarly re-
cites “Hypoxic Fire Prevention and Fire Suppression Sys-
tems and Breathable Fire Extinguishing Compositions for
Human Occupied Environments.” Id. The Board further
observed (without any citation) that “the Specification of
the ’752 Patent is indisputably directed to the problem of
fire prevention and fire suppression.” Id. Turning to Ko-
tliar, the Board found that the applicable field of endeavor
is “human therapy, wellness, and physical training.” Id.
For support, the Board quoted the title, “Hypoxic Room
System and Equipment for Hypoxic Training and Therapy
at Standard Atmospheric Pressure,” along with several
passages from the Field of the Invention section of Kotliar.
Id. (quoting Kotliar Title, col. 1 ll. 14–29). The Board also
emphasized that the term “fire” does not appear at all in
Kotliar. Id. Thus, the Board concluded that “Kotliar can-
not reasonably be said to be within the field of endeavor” of
the ’752 patent. Id. We cannot say that the Board’s finding
is unreasonable.
     Airbus contends that the Board’s determination is not
supported by substantial evidence because the Board failed
to identify adequate support in the specification and
claims. Airbus emphasizes that the Board only cited the
title of the ’752 patent and the preamble of a single claim
not at issue on appeal. While we agree that the Board’s
analysis could have been more developed, we disagree with
Airbus’s contention. A finding is supported by substantial
evidence if a “‘reasonable mind might accept’ a particular
evidentiary record as ‘adequate to support a conclusion.’”
Dickinson v. Zurko, 527 U.S. 150, 162 (1999) (quoting Con-
sol. Edison Co. of N.Y. v. NLRB, 305 U.S. 197, 229 (1938)).
In view of the Board’s factual findings that (1) the



    7  The challenged claims 91–94 include the same pre-
amble as claim 1.
12                             AIRBUS S.A.S. v. FIREPASS CORP.




challenged claims are expressly directed to a fire-preven-
tive and fire-suppressive system, and (2) Kotliar does not
even recite the word “fire” once throughout the entirety of
its disclosure, a reasonable mind could conclude that the
’752 patent and Kotliar are directed to different fields of
endeavor—especially for a “common sense” inquiry like
this. Bigio, 381 F.3d at 1326.
    Airbus does not point to any express disclosure in ei-
ther reference that directly contradicts the Board’s conclu-
sion. 8 Instead, Airbus argues that these two references
share the same function, “producing breathable hypoxic air
that is fire-preventative and fire-suppressive for a human-
occupied enclosure,” and the same structure, “a system
that includes an oxygen-extraction device (a nitrogen gen-
erator).” Appellant’s Br. 40. In support of this argument,
Airbus relies in part on the references that the Board de-
clined to consider—Gustafsson, the 1167 Report, Luria,
and Carhart—to argue that “a POSA would have known
and appreciated that the breathable hypoxic air produced
by Kotliar is fire-preventative and fire-suppressive, even
though Kotliar does not state this.” Id. at 41–42 (emphasis
added).
     We agree that the knowledge of a person of ordinary
skill in the art, as demonstrated by particular prior art ref-
erences, could be relevant to establishing the scope of the
field of endeavor. As discussed in greater detail in the fol-
lowing section, the Board should have considered Gus-
tafsson, the 1167 Report, Luria, and Carhart as record
evidence relevant to the knowledge and perspective of an
ordinarily skilled artisan at the time of the invention. But
to the extent the Board failed to do so here, its error is


     8    Indeed, the specification of each reference includes
a “Field of the Invention” section that distinctly describes
each applicable field of endeavor. Compare ’752 patent
col. 1 ll. 16–45, with Kotliar col. 1 ll. 13–29.
AIRBUS S.A.S. v. FIREPASS CORP.                           13



harmless. Even taking these additional prior art refer-
ences into account, we are not persuaded that a reasonable
factfinder could conclude that a person of ordinary skill
would understand that Kotliar—a reference that is ex-
pressly directed to exercise equipment and fails to mention
the word “fire” even a single time—falls within the field of
fire prevention and suppression. Such a conclusion would
not only defy the plain text of Kotliar, it would also defy
“common sense” and the “reality of the circumstances” that
a factfinder must consider in determining the field of en-
deavor. Bigio, 381 F.3d at 1326 (quoting Oetiker, 977 F.2d
at 1447). We therefore conclude that the Board’s determi-
nation under the field of endeavor test is supported by sub-
stantial evidence.
                              II
    We next address the Board’s application of the reason-
ably pertinent test. Outside of an inventor’s field of en-
deavor, “we only presume knowledge from those arts
reasonably pertinent to the particular problem with which
the inventor was involved.” Wood, 599 F.2d at 1036 (citing
In re Antle, 444 F.2d 1168, 1171–72 (C.C.P.A. 1971)). This
rule reflects the “reality of the circumstances” that “an in-
ventor could not possibly be aware of every teaching in
every art.” Id. Indeed, “[t]he pertinence of the reference as
a source of solution to the inventor’s problem must be rec-
ognizable with the foresight of a person of ordinary skill,
not with the hindsight of the inventor’s successful achieve-
ment.” Sci. Plastic Prods., Inc. v. Biotage AB, 766 F.3d
1355, 1359 (Fed. Cir. 2014) (first citing Oetiker, 977 F.2d
at 1447; then citing KSR Int’l Co. v. Teleflex Inc., 550 U.S.
398, 421 (2007)).
     Accordingly, a reference outside an inventor’s field of
endeavor is “reasonably pertinent” only if its subject mat-
ter “logically would have commended itself to an inventor’s
attention in considering his problem.” In re Clay, 966 F.2d
656, 659 (Fed. Cir. 1992). In other words, references are
14                            AIRBUS S.A.S. v. FIREPASS CORP.




“reasonably pertinent” only if “a person of ordinary skill
would reasonably have consulted those references and ap-
plied their teachings in seeking a solution to the problem
that the inventor was attempting to solve.” In re GPAC
Inc., 57 F.3d 1573, 1578 (Fed. Cir. 1995) (quoting Heidel-
berger Druckmaschinen v. Hantscho Commercial, 21 F.3d
1068, 1071 (Fed. Cir. 1994)). In GPAC, for example, we
found that a reference disclosing an equilibrium air door
was reasonably pertinent to a patent directed to asbestos
removal because they both addressed the same problem of
“maintaining a pressurized environment while allowing for
human ingress and egress.” Id. at 1578–79. But if the
problems addressed are substantially different, then the
references are not analogous. See Clay, 966 F.2d at 659–
60. In Clay, for example, we held that a reference that
sought to recover oil from rock was not reasonably perti-
nent to the problem of “preventing loss of stored product to
tank dead volume while preventing contamination of such
product”—even though both references generally related to
the petroleum industry. Id.
    In finding that Kotliar is not reasonably pertinent to
the problem of fire prevention and suppression, the Board
accurately observed that the examiner’s rejection did not
“provide or explain the requisite correlation” between the
problems addressed by Kotliar and the ’752 patent. J.A. 9.
But in doing so, the Board also expressly declined to con-
sider multiple references in the record that Airbus asserted
would establish the necessary link. Specifically, Airbus ar-
gued that four prior art references in the record—Gus-
tafsson, the 1167 Report, Luria, and Carhart—establish
that the use of normbaric hypoxic atmospheres in enclosed
environments was well-known in the art of fire prevention
and suppression at the time of the invention. Thus, accord-
ing to Airbus, an ordinarily skilled artisan seeking to ad-
dress the problem identified by the ’752 patent would
reasonably have consulted references relating to enclosed
hypoxic environments, such as Kotliar. While the four
AIRBUS S.A.S. v. FIREPASS CORP.                              15



references were considered by the examiner as part of other
obviousness combinations, the Board refused to consider
them because they were “not cited or applied in the pro-
posed rejection, and consequently, not fully addressed by
the Examiner or the Patent Owner as to their rele-
vancy . . . as to claim 91.” J.A. 13.
     We hold that the Board erred by refusing to consider
these references in support of the reasonably pertinent
test. Because a “reasonably pertinent” reference is one
that an ordinarily skilled artisan would reasonably have
consulted in seeking a solution to the problem that the in-
ventor was attempting to solve, the reasonably pertinent
inquiry is inextricably tied to the knowledge and perspec-
tive of a person of ordinary skill in the art at the time of the
invention. For example, the reasonably pertinent inquiry
may consider where an ordinarily skilled artisan would
reasonably look, and what that person would reasonably
search for, in seeking to address the problem confronted by
the inventor. In order to determine whether a reference is
“reasonably pertinent,” then, a reasonable factfinder
should consider record evidence cited by the parties to
demonstrate the knowledge and perspective of a person of
ordinary skill in the art at the time of the invention.
     The Gustafsson, the 1167 Report, Luria, and Carhart
prior art references are relevant to the question of whether
a person of ordinary skill in the art of fire prevention and
suppression would have reasonably consulted references
relating to normbaric hypoxic atmospheres to address the
problem of preventing and suppressing fires in enclosed en-
vironments. See Background § III, supra. These references
could lead a reasonable factfinder to conclude that an ordi-
narily skilled artisan in the field of fire prevention and sup-
pression would have looked to Kotliar for its disclosure of a
hypoxic room, even though Kotliar itself is outside the field
of endeavor.
16                              AIRBUS S.A.S. v. FIREPASS CORP.




     This court’s opinion in Randall Manufacturing v. Rea,
733 F.3d 1355 (Fed. Cir. 2013), is instructive. Randall sim-
ilarly involved an inter partes reexamination in which the
Board reversed the examiner’s obviousness rejection of sev-
eral patent claims. 733 F.3d at 1356. The Board rejected
the challenger’s proposed four-reference combination due
to a lack of motivation to combine. See id. at 1361. As here,
the challenger pointed to a host of other references that the
examiner had considered over the course of the examina-
tion—including some that had been the basis for rejecting
other claims—as background evidence establishing what a
person of ordinary skill would have known at the relevant
time. See id. at 1360. But the Board refused to consider
these background references, and instead limited its re-
view to the content of the four references in the asserted
combination. See id. at 1361.
     We vacated and remanded for the Board to consider the
background references. See id. at 1363–64. We explained
that KSR requires consideration of the “background
knowledge possessed by a person having ordinary skill in
the art,” and that our pre-KSR decisions consistently re-
quire consideration of common knowledge and common
sense. Id. at 1362 (quoting KSR, 550 U.S. at 418). We em-
phasized that “documentary evidence consisting of prior
art in the area” is “perhaps the most reliable” form of evi-
dence of what an ordinarily skilled artisan would have
known. Id. at 1362–63. As we explained:
     By narrowly focusing on the four prior-art refer-
     ences cited by the Examiner and ignoring the addi-
     tional record evidence [the challenger] cited to
     demonstrate the knowledge and perspective of one
     of ordinary skill in the art, the Board failed to ac-
     count for critical background information that
     could easily explain why an ordinarily skilled arti-
     san would have been motivated to combine or mod-
     ify the cited references to arrive at the claimed
     inventions.
AIRBUS S.A.S. v. FIREPASS CORP.                              17



Id. at 1362.
     Here, the Board distinguished Randall on the ground
that Randall concerned motivation to combine, not analo-
gous art. We do not agree that this is a meaningful basis
for distinction in this context. Motivation to combine and
the scope of analogous art are both factual inquiries under-
pinning an obviousness determination that take into ac-
count the knowledge and perspective of an ordinarily
skilled artisan. We therefore hold that the principles of
Randall should apply here with equal effect: an analysis of
whether an asserted reference is analogous art should take
into account any relevant evidence in the record cited by
the parties to demonstrate the knowledge and perspective
of a person of ordinary skill in the art. We accordingly va-
cate the Board’s reversal of the examiner’s rejection and
remand for the Board to reconsider its analogous art deter-
mination.
                         CONCLUSION
    We have considered the parties’ other arguments, and
we do not find them persuasive. For the foregoing reasons,
we vacate the Board’s reversal of the examiner’s rejection
and remand to the Board to consider whether Kotliar is
analogous art in view of the four prior art references relied
on by Airbus to demonstrate the knowledge and perspec-
tive of a person of ordinary skill in the art at the time of the
invention.
                VACATED AND REMANDED
                            COSTS
    No costs.
