               FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT


SECRETARY OF LABOR, U.S.                 No. 18-71216
Department of Labor,
                       Petitioner,         OSHC No.
                                            09-1901
                v.

SEWARD SHIP’S DRYDOCK, INC.,               OPINION
                    Respondent.


      On Petition for Review of an Order of the
  Occupational Safety & Health Review Commission

         Argued and Submitted June 13, 2019
                 Anchorage, Alaska

              Filed September 11, 2019

   Before: A. Wallace Tashima, William A. Fletcher,
         and Marsha S. Berzon, Circuit Judges.

            Opinion by Judge W. Fletcher
2           PIZZELLA V. SEWARD SHIP’S DRYDOCK

                            SUMMARY*


    Occupational Safety and Health Review Commission

    The panel granted the Secretary of Labor’s petition for
review of a decision of the Occupational Safety and Health
Review Commission interpreting a provision of the
Respiratory Protection Standard promulgated under the
Occupational Safety and Health Act of 1970, 29 C.F.R.
§ 1910.134.

    The panel adopted the Secretary’s interpretation of
§ 1910.134(d)(l)(iii), requiring covered employers to evaluate
the respiratory hazards at their workplaces whenever there is
the “potential” for overexposure of employees to
contaminants, in order to determine whether respirators are
“necessary to protect the health” of employees. The panel
held that the text, structure, purpose, and regulatory history of
the Standard all pointed in the same direction, and the panel
adopted the Secretary’s interpretation without resorting to
Auer deference.




    *
      This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
          PIZZELLA V. SEWARD SHIP’S DRYDOCK                 3

                        COUNSEL

Louise McGauley Betts (argued), Senior Attorney; Charles F.
James, Counsel for Appellate Litigation; Edmund C. Baird,
Acting Associate Solicitor of Labor for Occupational Safety
and Health; Kate O’Scannlain, Solicitor of Labor; United
States Department of Labor, Washington, D.C.; for Petitioner.

No appearance by Respondent.


                         OPINION

W. FLETCHER, Circuit Judge:

    We are asked to interpret a provision of the Respiratory
Protection Standard (“Standard”), promulgated under the
Occupational Safety and Health Act of 1970. 29 C.F.R.
§ 1910.134. Section 1910.134(a)(2) of the Standard provides,
“A respirator shall be provided to each employee when such
equipment is necessary to protect the health of such
employee.” The lead sentence of § 1910.134(d) provides,
“This paragraph requires the employer to evaluate respiratory
hazard(s) in the workplace[.]” Section 1910.134(d)(1)(iii),
whose meaning is at issue in this case, provides, “The
employer shall identify and evaluate the respiratory hazard(s)
in the workplace[.]”

    The Secretary of Labor (“Secretary”) has consistently
interpreted § 1910.134(d)(1)(iii) to require covered
employers to evaluate the respiratory hazards at their
workplaces whenever there is the “potential” for
overexposure of employees to contaminants, in order to
determine whether respirators are “necessary to protect the
4          PIZZELLA V. SEWARD SHIP’S DRYDOCK

health” of employees. In the case now before us, the
Occupational Safety and Health Review Commission
(“Commission”) disagreed with the Secretary.            The
Commission held that § 1910.134(d)(1)(iii) applies only
when respirators have already been determined to be
“necessary.” In the view of the Commission, the only
function of an evaluation under § 1910.134(d)(1)(iii) is to
provide guidance as to which respirator an employer should
use once respirators have been determined to be “necessary.”

    We have jurisdiction under 29 U.S.C. § 660(a). We adopt
the Secretary’s interpretation of § 1910.134(d)(1)(iii). We
accordingly grant the petition for review.

                  I. Regulatory Framework

    We begin with an overview of the Respiratory Protection
Standard. The Standard was promulgated under the
Occupational Safety and Health Act of 1970, 29 U.S.C.
§ 651, et seq., pursuant to the Secretary’s rulemaking
authority. The Standard was first issued in 1971. It applies
to industrial facilities in which respiratory hazards are likely
to be present. One such facility is a shipyard. 63 Fed. Reg.
1152, 1178–79 (January 8, 1998). The Standard is enforced
by the Occupational Safety and Health Administration
(“OSHA”).

    In its first subsection, the Standard describes its overall
purpose. The Standard seeks to “control . . . occupational
diseases caused by breathing air contaminated with harmful
dusts, fogs, fumes, mists, gases, smokes, sprays, or vapors[.]”
29 C.F.R. § 1910.134(a)(1). The “primary objective” of the
Standard is “to prevent atmospheric contamination.” Id. The
          PIZZELLA V. SEWARD SHIP’S DRYDOCK                5

Standard prescribes the methods by which employers should
protect their employees from contamination:

       [Protecting employees from atmospheric
       contamination] shall be accomplished as far
       as feasible by accepted engineering control
       measures (for example, enclosure or
       confinement of the operation, general and
       local ventilation, and substitution of less toxic
       materials).     When effective engineering
       controls are not feasible, or while they are
       being instituted, appropriate respirators shall
       be used pursuant to this section.

Id. The Standard provides that respirators must be provided
when “necessary”:

       A respirator shall be provided to each
       employee when such equipment is necessary
       to protect the health of such employee. The
       employer shall provide the respirators which
       are applicable and suitable for the purpose
       intended. . . .

Id. § 1910.134(a)(2) (emphasis added).

    The Standard does not define or describe the conditions
under which respirators are “necessary.” However, a separate
regulation specifies permissible exposure limits (“PELs”) for
various air contaminants. The regulation requires that
“administrative or engineering controls” be implemented to
keep exposures below the specified PELs. 29 C.F.R.
§ 1910.1000(e). If such controls do not achieve “full
compliance,” “protective equipment or any other protective
6         PIZZELLA V. SEWARD SHIP’S DRYDOCK

measures shall be used[.]” Id. Respirators are “protective
equipment.” PELs for specific contaminants are set forth in
three tables in § 1910.1000.

    Section 1910.134(d) of the Standard is titled “Selection of
respirators.” It begins, “This paragraph requires the
employer to evaluate respiratory hazard(s) in the workplace,
identify relevant workplace and user factors, and base
respirator selection on these factors.” (Emphasis added.)
Section (d)(1), “General requirements,” has four subsections.
One of them is § 1910.134(d)(1)(iii), the provision whose
meaning is at issue in this case. It provides in its entirety:

       The employer shall identify and evaluate the
       respiratory hazard(s) in the workplace; this
       evaluation shall include a reasonable estimate
       of employee exposures to respiratory
       hazard(s) and an identification of the
       contaminant’s chemical state and physical
       form. Where the employer cannot identify or
       reasonably estimate the employee exposure,
       the employer shall consider the atmosphere to
       be IDLH [immediately dangerous to life or
       health].

(Emphasis added.)

    Section 1910.134(d)(1)(iii) was added to the Standard in
1998. A lengthy “preamble” was published with the revised
Standard. The first two sentences addressing the newly added
section provide:

       Section (d)(1)(iii) of the final rule requires the
       employer to identify and evaluate the
          PIZZELLA V. SEWARD SHIP’S DRYDOCK                7

       respiratory hazard(s) in the workplace. To
       perform this evaluation, the employer must
       make a “reasonable estimate” of the employee
       exposures anticipated to occur as a result of
       those hazards, including those likely to be
       encountered in reasonably foreseeable
       emergency situations, and must also identify
       the physical state and chemical form of such
       contaminant(s).

63 Fed. Reg. at 1198 (emphasis added). The preamble goes
on to explain that “[m]any of the components of paragraph
(d)(1)(iii) of the final standard have been required practice
since 1971 because they were included in the selection
provisions of the 1969 ANSI [American National Standards
Institute] standard incorporated by reference into [the]
previous respiratory protection standard.” Id. Section
1910.134(d)(1)(iii) simply “makes these provisions clearer by
stating them explicitly in the regulatory text.” Id.

    An “OSHA Instruction,” interpreting the Standard, was
issued in 1998. A slightly revised Instruction was issued in
2014. The stated purpose of the Instruction in both versions
was (and is) as follows: “This Instruction establishes agency
interpretations and enforcement policies, and provides
instructions to ensure uniform enforcement of the Respiratory
Protection Standard[.]” Inspection Procedures for the
Respiratory Protection Standard, CPL 02-00-158, § I (June
26, 2014) (“2014 Instruction”); Inspection Procedures for the
Respiratory Protection Standard, CPL 2-0.120, § I (Sept. 25,
1998) (“1998 Instruction”). The 2014 Instruction provides:

       The employer is required to select and provide
       an appropriate respirator (NIOSH certified)
8          PIZZELLA V. SEWARD SHIP’S DRYDOCK

        based on the respiratory hazard(s) present in
        the workplace. The employer must identify
        hazardous airborne contaminants that
        employees may inhale and make a reasonable
        estimate of employee exposures in
        determining the appropriate respirator for
        employees to use. The employer must
        evaluate the respiratory hazards in the
        workplace where there is a potential for an
        employee overexposure.

2014 Instruction, at § IX(D) (emphasis added). The
comparable passage in the 1998 Instruction provided exactly
the same, but without the last sentence. 1998 Instruction, at
§ VII(E) (first two sentences). In a passage one page later,
the 1998 Instruction included a roughly equivalent sentence:

        If the employer has not made any effort to
        assess the respiratory hazards and there is the
        potential for an overexposure, the CSHO
        should cite section (d)(1)(iii).

Id. at § VII(E)(2) (first sentence) (emphasis added). The
critical point is that under both the 1998 and 2014
Instructions, employers were (and are) required to assess
respiratory hazards based on the “potential” for overexposure
of an employee. That is, an assessment for respiratory
hazards is required even if it turns out that respirators are not
“necessary to protect the health” of employees. The
assessment is required whenever there is a “potential” for
overexposure.

    With this framework in mind, we turn to the facts giving
rise to the present petition.
          PIZZELLA V. SEWARD SHIP’S DRYDOCK                  9

                   II. Factual Background

     In 2009, OSHA issued several citations to respondent
Seward Ship’s Drydock, Inc. (“Seward”) related to working
conditions on the Paula Lee, a deck barge. Seward was a
marine vessel repair business located in Seward, Alaska. It
performed both “drydock” repairs, where the vessel is out of
the water, and “dockside” repairs, where the vessel is floating
in the water. According to the Secretary, respondent Seward
no longer conducts repairs but still exists as an employer and
would be subject to any penalty assessed. Seward elected not
to file an answering brief in this court and did not appear for
oral argument.

     In February 2009, Seward performed welding work in the
voids of the Paula Lee. “Voids” are compartments in a deck
barge that can be left empty to provide buoyancy or can be
filled with water to provide ballast. Prior to beginning
repairs, Seward obtained a “Marine Chemist Certificate” from
Joseph Graham, a certified marine chemist. Graham
inspected the drydocked Paula Lee, tested the oxygen levels
in each void, and tested for combustible gases and toxic
substances. Graham certified the vessel as safe for drydock
welding (also known as “hot work”) on February 9, 2009. As
is customary for purposes of a Marine Chemist Certificate,
Graham was not told what types of welding rods Seward
planned to use. Graham therefore could not test for fumes
that would be produced by welding. Indeed, Graham testified
in the administrative hearing, “I don’t know how to test for
welding fumes.”

    Seward spent five weeks conducting extensive repairs
through “production welding,” which involves long,
continuous welds of large plates of replacement steel. On
10        PIZZELLA V. SEWARD SHIP’S DRYDOCK

April 11, 2009, Seward refloated the Paula Lee and placed it
dockside. A few days later, Seward discovered the need for
additional “pick-up” work, which involved spot welding of
seams that were not fully closed during production welding.

    Seward spent three days performing pick-up work, from
April 14 through April 16. Employees spent up to ten hours
per day in voids of the Paula Lee in order to meet the
project’s April 17 deadline. The voids were located
underneath the main deck and were accessible only through
manholes approximately 19 inches wide. Respirators were
offered on a voluntary basis, and at least one welder used a
respirator.

     Each morning before welding began, Larry Williams, the
site’s superintendent and the designated “shipyard competent
person,” conducted atmospheric testing in the areas where
work would take place. As the shipyard competent person,
Williams was responsible for maintaining the conditions
described in the Marine Chemist Certificate. Before welding
began, Williams tested the voids using a “grab sample,”
which provides an immediate measurement from a gas meter.
His tests determined whether the spaces were “safe for entry”
at the time the test was performed.

    Williams’s pre-welding sampling did not test for the
metals found in welding fumes. Welding fumes have
different constituent elements depending on the composition
of the electrode—or welding rod—used during welding.
According to material safety data sheets, the two types of
electrodes used on the Paula Lee contained iron oxide,
manganese, fluorides, and barium compounds. Overexposure
to these substances can cause both short- and long-term
respiratory difficulties. For example, overexposure to iron
          PIZZELLA V. SEWARD SHIP’S DRYDOCK                 11

oxide can cause a condition called “siderosis,” commonly
known as “iron lung.”

     Henry “Joe” Hogge and Bruce Whitmore worked as
welders on the Paula Lee. They testified at the administrative
hearing about the conditions they experienced during the
pick-up work. Hogge described the air quality within the
voids as “extremely poor.” He testified that there was
“inadequate ventilation” in the void because the fan placed
over the manhole cover to provide forced ventilation pulled
out fumes only from the top of the void, leaving fumes near
the bottom of the void where the welders were working. The
void filled “quite quickly” with welding fumes, making it
“very smokey . . . to the point where visibility was bad and it
was difficult to breathe in.” “It was a lot of brown smoke, a
lot of welding fumes. . . . [T]he ventilation was so poor that
Bruce and I both came in one day and we couldn’t hardly
even speak. [O]ur—our voices were—were very raspy[,] and
I attribute that to the smoke.” Whitmore similarly described
the “smoke conditions from welding” as “terrible.” He
testified that the “air handlers and smoke exhaust fans were
not working.” The smoke “was very, very thick.” “I had lost
my voice. Joe had lost his voice. And it was—it was a
continuous thing.”

    On April 14, after welding had begun, Hogge and
Whitmore complained about the smoke and lack of effective
ventilation. Hogge testified that he “complained about [how]
there had been no air monitoring done that day, and we were
expected to go into the hole.” In response, Williams
conducted a “grab sample” by lowering an “air monitor”
about six inches into a void. Hogge testified that when
Williams put the monitor into the void, there was “an audible
alarm.” Whitmore asked Williams what it meant. Hogge
12        PIZZELLA V. SEWARD SHIP’S DRYDOCK

testified that Williams replied, “It’s to let you know you’re
still alive.” Whitmore testified similarly: “And he says it
meant—it means you’re alive, you know, or some
derogatory—some kind of statement like that. And I said,
‘Well, what does that mean?’ And there was no response.”

   Hogge and Whitmore called OSHA on April 14 to make
a complaint. OSHA dispatched two compliance officers,
Mathew Pauli and John Casper, to inspect the Paula Lee.
Pauli and Casper were on site during the evening of April 14
and during the day of April 15.

    Pauli and Casper testified that upon arriving the evening
of April 14, they observed welders working in a void without
adequate ventilation and with visible welding fumes. The
following day, Pauli and Casper took two “grab samples” to
test for carbon monoxide and fitted two welders with
“personal exposure monitoring” devices to test for iron oxide
and other possible contaminants.           Personal exposure
monitoring requires employees to wear a measuring device
for a sustained period. The device samples the air and
identifies the chemicals and contaminants, and their
concentrations, to which an employee is exposed. OSHA
considers personal exposure monitoring the “gold standard”
of air testing because it is more reliable than other forms of
testing such as grab samples. 63 Fed. Reg. at 1199.

    The results of the personal exposure monitoring were
placed into the record in the administrative hearing for only
one of the two employees. As discussed above, respirators
are “necessary” if exposure to an air contaminant exceeds
OSHA’s PEL for that contaminant. OSHA’s PELs are based
on an eight-hour “time-weighted average,” which measures
the average concentration of a substance over that time
          PIZZELLA V. SEWARD SHIP’S DRYDOCK                13

period. The PEL for iron oxide is 10 milligrams per cubic
meter for eight hours. The personal exposure monitor on the
Seward employee measured an exposure of 9.1 milligrams
per cubic meter for 6.5 hours.

    Following the inspection and testing, OSHA issued a
“Citation and Notification of Penalty” alleging thirteen
violations of the Occupational Safety and Health Act. A
hearing was conducted before an Administrative Law Judge
(“ALJ”) in March 2011. The ALJ sustained a number of the
citations, assessing a total penalty of $34,000. The ALJ
vacated the citation at issue in the petition before
us—Citation 1, Item 3. That citation alleged as follows:

       29 C.F.R. § 1910.134(d)(1)(iii):         The
       employer did not identify and evaluate the
       respiratory hazard(s) in the workplace to
       include a reasonable estimate of employee
       exposures to respiratory hazard(s) and an
       identification of the contaminant’s chemical
       state and physical form . . . : Paula Lee
       Barge: On or about April 14, 2009 and at
       times prior thereto, respiratory hazards for
       welders and helpers working in confined
       spaces had not been evaluated. This condition
       exposed employees to inhalation hazards.

    Seward argued to the ALJ that it had complied with
§ 1910.134(d)(1)(iii) because a certified marine chemist had
tested the voids in the Paula Lee and certified them as safe
for hot work. The ALJ agreed. After recounting the testing
done by Joseph Graham, the ALJ wrote, “[T]he Marine
Certificate on its face indicated an evaluation of respiratory
hazards with no conditions which required correction. . . .
14         PIZZELLA V. SEWARD SHIP’S DRYDOCK

Therefore, the court concludes that Respondent did evaluate
the respiratory hazards on the Paula Lee.”

    The Secretary petitioned the Occupational Safety and
Health Review Commission for review of the ALJ’s decision
to vacate Citation 1, Item 3. In 2012, the parties conducted
a full round of briefing on whether Seward had adequately
evaluated respiratory hazards in compliance with
§ 1910.134(d)(1)(iii).

    Over a year later, on April 17, 2013, the Commission sua
sponte asked the parties to submit supplemental briefing on
“whether the requirement to ‘identify and evaluate the
respiratory hazard(s) in the workplace’ under
§ 1910.134(d)(1)(iii) is contingent on the Secretary showing
that respirators were ‘necessary to protect the health of
[Seward’s] employee[s]’ under § 1910.134(a)(2).” (Second
alteration in original.) The parties’ prior briefing, as well as
the ALJ’s decision, had been premised on the understanding
that § 1910.134(d)(1)(iii) required employers to evaluate
respiratory hazards as an initial matter to determine whether
respirators are necessary under § 1910.134(a)(2). Neither the
parties nor the ALJ had understood § 1910.134(d)(1)(iii) to
require evaluation of respiratory hazards only after a
determination had been made that respirators were necessary.

    More than four years after the conclusion of supplemental
briefing, the Commission unanimously concluded that
§ 1910.134(d)(1)(iii) is unambiguous, and that it requires an
evaluation of respiratory hazards only when respirators are
“necessary to protect the health” of employees under
§ 1910.134(a)(2). In the alternative, the Commission held
that even if the language is ambiguous, the Secretary’s
interpretation is unreasonable and not entitled to deference.
           PIZZELLA V. SEWARD SHIP’S DRYDOCK                   15

    Two Commissioners concluded that the Secretary had
failed to prove that air contaminants were present at levels
that made the use of respirators “necessary,” and that Seward
had therefore not been required to perform an evaluation
under § 1910.134(d)(1)(iii). The third Commissioner
dissented, concluding that the Secretary established that
respirators had been “necessary” and that an evaluation under
§1910.134(d)(1)(iii) was therefore required.

    The Secretary petitioned for review in this court.

      III. Meaning of 29 C.F.R. § 1910.134(d)(1)(iii)

    “[W]e presume that Congress intended for courts to defer
to agencies when they interpret their own ambiguous rules.”
Kisor v. Wilkie, 139 S. Ct. 2400, 2414 (2019). In the case of
OSHA regulations like the one at issue here, “a reviewing
court may not prefer the reasonable interpretations of the
Commission to the reasonable interpretations of the
Secretary.” Martin v. Occupational Safety & Health Review
Comm’n, 499 U.S. 144, 158 (1991). But, as the Supreme
Court wrote in Kisor, “The possibility of deference can arise
only if a regulation is genuinely ambiguous[,] . . . even after
a court has resorted to all the standard tools of interpretation.”
139 S. Ct. at 2414. To determine whether a regulation’s
meaning is truly ambiguous, courts must “carefully consider
the text, structure, history, and purpose of a regulation.” Id.
at 2415 (internal quotation marks omitted). “Doing so will
resolve many seeming ambiguities out of the box.” Id.

    We conclude that § 1910.134(d)(1)(iii) is sufficiently
clear that it is not “genuinely ambiguous” under Kisor.
Section 1910.134(d)(1)(iii) requires covered employers to
evaluate respiratory hazards that exist in the workplace in
16        PIZZELLA V. SEWARD SHIP’S DRYDOCK

order to determine whether respirators must be provided.
There is no threshold requirement that respirators be found
“necessary” in order to trigger such an evaluation.

          A. Text and Structure of the Regulation

    We begin with the text and structure of
§ 1910.134(d)(1)(iii). “A regulation should be construed to
give effect to the natural and plain meaning of its words.”
Bayview Hunters Point Cmty. Advocates v. Metro. Transp.
Comm’n, 366 F.3d 692, 698 (9th Cir. 2004) (quoting Crown
Pacific v. Occupational Safety & Health Review Comm’n,
197 F.3d 1036, 1038 (9th Cir. 1999)).

    Section 1910.134(d)(1)(iii) requires an employer to
“identify and evaluate the respiratory hazard(s)” in the
workplace. The dictionary defines “hazard” in relevant part
to mean “a thing or condition that might operate against
success or safety: a possible source of peril, danger, duress,
or difficulty.” Webster’s Third New International Dictionary
Unabridged (1961) (emphases added); see also Oxford
English Dictionary Online (defining hazard as “a physical
object which is regarded as a source of potential difficulty or
danger”) (last visited July 30, 2019) (emphasis added).
Consistent with this definition, the Secretary has interpreted
§ 1910.134(d)(1)(iii) to require evaluation of respiratory
hazards whenever there is “potential” for overexposure of
employees.

    The Commission disagreed with this interpretation of
§ 1910.134(d)(1)(iii).         Under the Commission’s
interpretation, § 1910.134(d)(1)(iii) is triggered only if a
respirator is “necessary to protect the health” of employees
under § 1910.134(a)(2).            The sole purpose of
           PIZZELLA V. SEWARD SHIP’S DRYDOCK                  17

§ 1910.134(d)(1)(iii), according to the Commission, is to
enable the employer to choose the correct respirator. The
Commission wrote, “This requires the Secretary to show
there was a significant risk of harm necessitating the use of
respirators.” See Weirton Steel Corp., 20 BNA OSHC 1255,
1259 (No. 98-0701, 2003). A “significant risk of harm”
exists if “a reasonable person familiar with the circumstances
surrounding an allegedly hazardous condition . . . would
recognize a hazard warranting the use of protective
equipment.” See Owens-Corning Fiberglass Corp., 7 BNA
OSHC 1291, 1295 (No. 76-4990, 1979), aff’d on other
grounds, 659 F.2d 1285 (5th Cir. 1981). More specifically,
as we noted above, respirators are “necessary” under the
Secretary’s regulations if the exposure level for a specified air
contaminant exceeds OSHA’s maximum permissible
exposure limit for that contaminant.                29 C.F.R.
§1910.1000(e).

    The Commission gave two reasons for its reading of
§ 1910.134(d)(1)(iii). Neither is persuasive.

    First, the Commission wrote that the word “the” before
“respiratory hazard(s)” “plainly presumes that such hazards
are present and directs the employer to assess them; the
provision does not state that the employer must evaluate the
workplace for such hazards.” (Emphasis in original.) The
Commission is not correct that § 1910.134(d)(1)(iii)
“presumes that [respiratory] hazards are present.” Section
1910.134(d)(1)(iii) requires employers to both “identify and
evaluate the respiratory hazard(s) in the workplace.”
(Emphasis added.) The word “identify” indicates that,
contrary to the Commission’s analysis, the regulation applies
even where an employer does not already know of hazards in
the workplace. And, the fact that employers must “identify
18         PIZZELLA V. SEWARD SHIP’S DRYDOCK

. . . the respiratory hazard(s) in the workplace” indicates that
in some circumstances, employers carrying out such duty will
identify no such hazards.

    In light of the clear meaning expressed by the term
“identify,” the Commission’s dispositive reliance on the
regulation’s use of the word “the” was improper. Where, as
here, there are better indicators of a regulation or statute’s
meaning, we have rejected excessive reliance on the
distinction between definite articles such as “the” and
indefinite articles such as “a” and “any.” See, e.g., Ileto v.
Glock, Inc., 565 F.3d 1126, 1145–46 (9th Cir. 2009); City of
Ketchikan v. Cape Fox Corp., 85 F.3d 1381, 1384 (9th Cir.
1996); see also Hernandez v. Williams, Zinman & Parham
PC, 829 F.3d 1068, 1074 (9th Cir. 2016); NLRB v. New Vista
Nursing & Rehab., 719 F.3d 203, 227–28 (3d Cir. 2013).

    Second, the Commission placed great weight on the
location of § 1910.134(d)(1)(iii) in the subsection titled
“Selection of respirators,” “alongside provisions that deal
exclusively with either respirator selection factors or
respirator specifications.” To start, “the title of a statute and
the heading of a section cannot limit the plain meaning of the
text.” Brotherhood of R.R. Trainmen v. Balt. & Ohio R.R.
Co., 331 U.S. 519, 528–29 (1947). Further, it is not
unreasonable to include a provision requiring employers to
assess whether it is necessary to select a respirator within a
subsection on the “selection of respirators.”

         B. Purpose and History of the Regulation

    We thus find little or no ambiguity in the plain text of the
regulation. Any ambiguity that might remain is dispelled by
the purpose of the Standard and its regulatory history. See
           PIZZELLA V. SEWARD SHIP’S DRYDOCK                  19

Kisor, 139 S. Ct. at 2415 (“[B]efore concluding that a rule is
genuinely ambiguous, a court must exhaust all the ‘traditional
tools’ of construction. . . . To make that effort, a court must
‘carefully consider[ ]’ the text, structure, history, and purpose
of a regulation[.]” (emphasis added)).

    The Standard’s “primary objective” is “to prevent
atmospheric contamination” in order to prevent employees
working in industrial facilities from experiencing
“occupational diseases caused by breathing air contaminated
with harmful dusts, fogs, fumes, mists, gases, smokes, sprays,
or vapors.” 29 C.F.R. § 1910.134(a)(1). To achieve this
goal, the Standard requires an employer first to put in place
engineering control measures, such as ventilation, as feasible.
Only if those measures are not feasible or are inadequate is
the employer required to use respirators. See id. Under the
Commission’s reading, employers would be required to
evaluate respiratory hazards only after it becomes clear that
employees will be overexposed without a respirator. But
such a reading undermines the Standard’s goals of preventing
exposure to atmospheric contamination in the first place.
Without an initial evaluation of respiratory hazards,
employers would not be able to assess whether the
engineering control measures they employ—if any—are
sufficiently protective of employee health.

    The regulatory history of the Standard also supports our
reading. In the preamble to the Standard, the discussion of
§ 1910.134(d)(1)(iii) begins,

        Paragraph (d)(1)(iii) of the final rule requires
        the employer to identify and evaluate the
        respiratory hazard(s) in the workplace. To
        perform this evaluation, the employer must
20        PIZZELLA V. SEWARD SHIP’S DRYDOCK

       make a “reasonable estimate” of the employee
       exposures anticipated to occur as a result of
       those hazards, including those likely to be
       encountered in reasonably foreseeable
       emergency situations, and must also identify
       the physical state and chemical form of such
       contaminant(s).

63 Fed. Reg. at 1198 (emphasis added). The “exposures
anticipated to occur” plainly include all exposures, not just
those that exceed a contaminant’s permissible exposure limit.
This text directly contradicts the Commission’s
understanding that actual or anticipated overexposure is a
prerequisite to a § 1910.134(d)(1)(iii) evaluation.

    The preamble’s discussion of the appropriate tools for an
evaluation under § 1910.134(d)(1)(iii) reiterates the purpose
of that evaluation. The preamble states, “OSHA recognizes
that there are many instances in which it may not be possible
or necessary to take personal exposure measurements to
determine whether respiratory protection is needed.” Id. at
1199 (emphasis added). The preamble then discusses
alternate acceptable methods to estimate exposure, such as
data from industry-wide surveys and mathematical analysis.
See id. The preamble continues that, under certain
circumstances, employers may nonetheless “find it easier and
less costly to conduct personal exposure monitoring to
evaluate the need for respiratory protection.” Id. (emphasis
added). OSHA clearly intended for an evaluation to first
determine whether a respirator is necessary, and only if a
respirator is necessary, to use that evaluation to choose the
appropriate type of respirator.
           PIZZELLA V. SEWARD SHIP’S DRYDOCK                 21

    Enforcement guidance issued contemporaneously with the
Standard in 1998 further confirms our reading. As noted
above, the 1998 OSHA Instruction stated, “If the employer
has not made any effort to assess the respiratory hazards, and
there is potential for an overexposure, the [compliance
officer] should cite section (d)(1)(iii).” See 1998 Instruction,
at § VII(E)(2) (emphasis added). The Instruction also
recognized the employer’s “continuing” obligation under
§ 1910.134(d)(1)(iii) to “identify hazards as a result of
changes in the workplace” and then provide “[a]ppropriate
respirators . . . as necessary.” Id. at § VII(E) (emphasis
added). This flatly contradicts the Commission’s reading that
§ 1910.134(d)(1)(iii) operates only when respirators are
already necessary.

                           Conclusion

    The text, structure, purpose, and regulatory history of the
Standard all point in the same direction. We adopt the
Secretary’s interpretation of § 1910.134(d)(1)(iii) without
resorting to Auer deference. Using “all the ‘traditional tools’
of construction,” we conclude that § 1910.134(d)(1)(iii) is not
truly ambiguous. See Kisor, 139 S. Ct. at 2415. We hold that
29 C.F.R. § 1910.134(d)(1)(iii) requires an evaluation of
which, if any, respiratory hazards exist in a workplace where
there is a potential for overexposure of employees.

   We grant the petition and remand for further proceedings
consistent with this opinion.

   GRANTED           and     REMANDED           for    further
proceedings.
