the remoteness of interference with patient care are considered, it was irrational to strike the balance in favor of § 7 rights in the hospital cafeteria and against them in public restaurants. The Board's explanation of the consistent principle underlying the different results in each situation cannot fairly be challenged. St. John's Hospital & School of Nursing, Inc., 222 N. L. R. B., at 1150-1151, n. 3.

IV

In summary, we reject as without merit petitioner's contention that, in enacting the 1974 health-care amendments, Congress intended the Board to apply different principles regarding no-solicitation and no-distribution rules to hospitals because of their patient-care functions. We therefore hold that the Board's general approach of requiring health-care facilities to permit employee solicitation and distribution during nonworking time in nonworking areas, where the facility has not justified the prohibitions as necessary to avoid disruption of health-care operations or disturbance of patients, is consistent with the Act. We hold further that, with respect to the application of that principle to petitioner's cafeteria, the Board was appropriately sensitive to the importance of petitioner's interest in maintaining a tranquil environment for patients. Insofar as petitioner's challenge is to the substantiality of the evidence supporting the Board's conclusions, this Court's review is, of course, limited. "Whether on the record as a whole there is substantial evidence to support agency findings is a question which Congress has placed in the keeping of the Courts of Appeals. This Court will intervene only in what ought to be the rare instance when the standard appears to have been misapprehended or grossly misapplied." Universal Camera Corp. v. NLRB, 340 U. S. 474, 491 (1951). We cannot say that the Court of Appeals' assessment of the record either "misapprehended" or "grossly misapplied" that standard. The Court of Appeals did note, however, that the

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437 U.S.

Board's guidelines are still in flux and are far from self-defining, concluding, and we agree:

"[T]he Board [bears] a heavy continuing responsibility to review its policies concerning organizational activities in various parts of hospitals. Hospitals carry on a public function of the utmost seriousness and importance. They give rise to unique considerations that do not apply in the industrial settings with which the Board is more familiar. The Board should stand ready to revise its rulings if future experience demonstrates that the wellbeing of patients is in fact jeopardized." 554 F. 2d, at 481.

The authority of the Board to modify its construction of the Act in light of its cumulative experience is, of course, clear. NLRB v. Iron Workers, 434 U. S., at 351; NLRB v. Weingarten, Inc., 420 U. S., at 265–267.

Affirmed.

MR. JUSTICE BLACKMUN, with whom THE CHIEF JUSTICE and MR. JUSTICE REHNQUIST join, concurring in the judgment.

I concur only in the result the Court reaches here, for I, too, agree with much that MR. JUSTICE POWELL says in his separate opinion.

There is, of course, a certain irony when the Board grants protection from solicitation to the retail store and to the Burger Chef and the Hot Shoppe cafeteria, but at the same time denies it to the hospital restaurant facility where far more than mere commercial interests are at stake. Patients and their concerned families are not to be treated as impersonal categories or classes. They are individuals with problems that ought not be subject to aggravation. Nevertheless, on this record, as the Court's opinion reveals, it would have been difficult for the Board to reach a different result, when it utilized, questionably in my view, the rule of Republic Aviation Corp. v. NLRB, 324 U. S. 793 (1945), even as perhaps modified for application in the hospital setting.

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POWELL, J., concurring in judgment

The tenor of the Court's opinion and of the Board's approach concerns me. There are many hospital coffeeshops and cafeterias that are primarily patient and patient-relative oriented, despite the presence of employee patrons, far more so than this very restricted Beth Israel operation, that seems akin to a manufacturing plant's emloyees' cafeteria. I fear that this unusual case will be deemed to be an example for all hospital eating-facility cases, and that the Board and the courts now will go further down the open-solicitation road than they would have done, had a more usual hospital case been the one first to come here. Hospitals, after all, are not factories or mines or assembly plants. They are hospitals, where human ailments are treated, where patients and relatives alike often are under emotional strain and worry, where pleasing and comforting patients are principal facets of the day's activity, and where the patient and his family-irrespective of whether that patient and that family are labor or management oriented-need a restful, uncluttered, relaxing, and helpful atmosphere, rather than one remindful of the tensions of the marketplace in addition to the tensions of the sickbed.

I entertain distinct doubts about whether the Board, in its preoccupation with labor-management problems, has properly sensed and appreciated the true hospital operation and its atmosphere and the institution's purpose and needs. I earnestly share the caveat pronounced by the Court of Appeals, and reproduced by the Court in the next-to-the-last paragraph of its opinion, ante, at 508, and I sincerely hope that the Board bears that heavy responsibility in mind when it considers other hospital cases that come before it for decision.

MR. JUSTICE POWELL, with whom THE CHIEF JUSTICE and MR. JUSTICE REHNQUIST join, concurring in the judgment.

In Republic Aviation Corp. v. NLRB, 324 U. S. 793 (1945), this Court approved the reasoning of the National Labor Relations Board in Peyton Packing Co., 49 N. L. R. B. 828

POWELL, J., concurring in judgment

437 U.S.

(1943), enf'd, 142 F. 2d 1009 (CA5), cert. denied, 323 U. S. 730 (1944), and the balance it struck in adjusting the respective rights of industrial employers and employees. The Court also endorsed the Board's formulation: Because working time is for work, a rule prohibiting union solicitation during working time "must be presumed to be valid in the absence of evidence that it was adopted for a discriminatory purpose" "; but during nonworking time, when an employee's time is his own even though he is on company property, a rule prohibiting union solicitation "must be presumed to be an unreasonable impediment to self-organization and therefore discriminatory in the absence of evidence that special circumstances make the rule necessary in order to maintain production or discipline.'" 324 U. S., at 803-804, n. 10 (quoting Peyton Packing Co., supra, at 843-844).

The Republic Aviation rule is inapplicable in the instant case, which arises from a setting entirely different from the one in which the rule was formulated. I concur in the judgment of the Court, however, because I regard the Board's decision as based on substantial evidence even without the assistance of the Republic Aviation presumption.

I

The rule of Republic Aviation was adopted in the context of labor relations in industrial and manufacturing plants, where third parties unconnected with labor or management generally are not involved. In such a setting, it is relatively simple to divide the work environment into the two spheres defined in Peyton Packing. During working time an employer's prohibition of solicitation and distribution may be presumed valid, because "[w]orking time is for work"; but during nonworking time or in nonworking areas, such rules are presumptively invalid. The latter part of the Board's set of presumptions reflects the reasonable inference, based on the Board's experience with the actual facts of industrial life, that

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POWELL, J., concurring in judgment

such employers ordinarily will not have legitimate reasons to restrict employees' activities on their own time, even if on company property. In sustaining the Board's presumption, this Court recounted its development and said:

"We perceive no error in the Board's adoption of this presumption. The Board had previously considered similar rules in industrial establishments and the definitive form which the Peyton Packing Company decision gave to the presumption was the product of the Board's appraisal of normal conditions about industrial establishments. Like a statutory presumption or one established by regulation, the validity, perhaps in a varying degree, depends upon the rationality between what is proved and what is inferred." 324 U. S., at 804-805 (footnotes omitted; emphasis supplied).

The rationality found to exist in Republic Aviation, and therefore the validity of the presumption, cannot be transferred automatically to other workplaces, for to do so would sever the connection between the inference and the underlying proof. The Court's approval of the Republic Aviation rule was based explicitly on the Board's considered appraisal of "normal conditions about industrial establishments." Conditions in industrial or manufacturing plants differ substantially from conditions in sales and service establishments where employees and members of the public mingle.

When confronted with the problem of retail-establishment rules prohibiting solicitation and distribution, the Board wisely refrained from mechanically applying the Republic Aviation rule when its justification was absent. The Board recognized that in the setting of a retail establishment, an employer well

1 Even the formulation of the "special circumstances" rule is stated in terms of the specific environment of an industrial plant, speaking of circumstances making a restriction on employee activity "necessary in order to maintain production or discipline.'" 324 U. S., at 803-804, n. 10.