SECRETARY OF LABOR. Complainant. v. PRIDE OIL WELL SERVICE, Respondent. OSHRC Docket No. 87-0692 /DECISION / Before:FOULKE, Chairman: WISEMAN and MONTOYA, Commissioners. BY THE COMMISSION: As a result of an accident investigation and inspection by the Occupational Safety and Health Administration ("OSHA"), Pride Oil Well Service ("Pride") was charged with serious violations of standards promulgated under the Occupational Safety and Health Act of 1970, 29 U.S.C. §§ 651-678 ("the Act"), because it failed to provide: (1) respiratory protection to employees involved in monitoring the contents of a mobile storage tank from an opening in its top; or (2) a sign warning of potential hazards or unsafe practices involving the tank. At issue is whether Review Commission Administrative Law Judge E. Carter Botkin erred in concluding that Pride committed these alleged violations. I. /Background/ Pride is an oil well service company with its principal office located in Houston, Texas. Pride and several other subcontractors had crews working to restore a well in Angleton, Texas, to be operational again. Tommy Mostyn, a drilling consultant, had been hired by the owner of the well to oversee the entire project. Mostyn, in turn, gave directions to George Cantu, Pride's rig supervisor, or "tool pusher," who was responsible for supervising Pride's crew. As part of the process to "recomplete" the well, another subcontractor used tubing to insert liquid nitrogen, under pressure, into the well to force diesel oil, water, and other materials from the well bore and into a 500-gallon "frac tank," or mobile storage tank ("the tank"). During this process, liquid nitrogen changed into nitrogen vapor or gas, an odorless asphyxiant, that combines with the vapors or gases from the diesel oil and other hydrocarbons present in the tank to form a gaseous mixture that is heavier than air. This mixture then displaces the oxygen in the tank, forcing it out through the tank's vent holes. In order to determine how deeply to drill, Mostyn needed to know the level of the "returns," or the fluid that was coming out of the well and into the tank. He ordered Cantu to have an employee go up onto the top of the tank to monitor the flow of the "returns" from an opening there, but Cantu protested. Cantu testified that he told Mostyn that it was unnecessary to have employees on top of the tank because he "had already rigged up a way to get a sample off the needle valve" which was observable from the ground. When Mostyn persisted, Cantu relented and assigned Mario Perez, a Pride floor hand, to go up on the tank to observe the level of the "returns." The opening in the top of the tank through which the level of the "returns" could be observed measured 18-1/2 inches square, with a hatchway cover that had been left open for monitoring purposes. Nearby, there was a small, circular hole that measured three inches in diameter. There was a ladder on the exterior of the Tank leading to its top, but no ladder leading down into the interior of the tank. Perez testified that he had to kneel and look down into the hatchway opening, sometimes sticking his head through the opening, in order to perform his assignment to check the flow of the liquid. [[1]] To relieve Perez for lunch, Cantu assigned Rodrigo Reyes, another Pride floor hand, to go up on the tank. When Perez came down, Cantu was talking with another Pride employee, Arnoldo Zamora. Cantu testified that Perez asked him what was coming out of the well because it was "making [him] real dizzy" and "making [his] head hurt." Cantu responded that, as far as he knew, diesel, nitrogen, and some gas were coming out of the well. When Perez told Cantu that he was not going back up, Cantu said that was "[f]ine" and went for a coffee break. Cantu testified that when he left for that break, he saw Reyes sitting within one to two feet of the hatchway opening. [[2]] About five minutes after Cantu had gone on his break, Mostyn went into the trailer house and told Cantu that one of his men had fallen into the tank. Cantu climbed on top of the tank, after having learned that one of the older Pride employees had already responded to the accident by closing the wing valve at the well head. When he called for Zamora, whom he had spoken to before taking the break, another employee told Cantu that Zamora also had gone into the tank, apparently for a rescue attempt. When Cantu observed through the opening a body floating that still had hand movement, he took a deep breath and entered the tank. However, this rescue attempt was unsuccessful. Cantu himself became dizzy and weak in his knees and then collapsed. Not until an air hose was thrown down to him was Cantu able to breathe sufficiently to climb out of the tank. The autopsy reports stated that both Reyes and Zamora had died as a result of: "Asphyxia due to drowning (diesel and H2O)." Also noted in Reyes' autopsy report was the presence of "[m]ultiple abrasions and contusions" on the upper front of the head. The judge found that these "abrasions and contusions" were consistent with Reyes having lost consciousness and then falling into the tank. The opinion of the forensic pathologist, who performed the autopsies, was that each employee died "as a result of asphyxia due to drowning, accidental, while at work." It is undisputed that Pride did not provide any respiratory protection to these employees, nor was there any sign posted to caution employees regarding potential hazards or unsafe practices involving the contents of the tank. When asked if the employees had been "trained in any way about oxygen-deficient atmospheres," Pride's supervisor Cantu testified that he personally had not been. He further testified that there was no equipment at the worksite for testing the oxygen level in the tank. Moreover, the OSHA compliance officer who conducted the investigation and the inspection testified that she concluded that Pride employees had not been given any training in oxygen deficiency, and that "[s]ome of them didn't even know what it was." Following the OSHA investigation and inspection, Pride was issued a citation alleging, as amended in the complaint, serious violations of the respiratory protection standard at 29 C.F.R. § 1910.134(a)(2) and the caution sign standard at 29 C.F.R. § 1910.145(c)(2)(i). [[3]] On April 2, 1990, this case was directed for review on issues relating to the judge's affirmance of these two citation items. II. Respiratory Protection Citation no. 1, item 2, as amended, alleges that Pride committed a serious violation of 29 C.F.R. § 1910.134(a)(2) [[4]] by failing to provide respiratory protection to employees involved in monitoring the "returns," as well as those employees who had attempted rescue. In order to establish a violation of a specific standard, the Secretary must prove by a preponderance of the evidence that: the standard applies to the cited condition; the employer failed to meet the terms of the standard; its employees had access to the violative condition; and the employer either knew or could have known of the condition with the exercise of reasonable diligence. E.g., Astra Pharmaceutical Prods., 9 BNA OSHC 2126, 2129, 1981 CCH OSHD 25,578, pp.31,899-900(No. 78-6247, 1981), aff'd in pertinent part, 681 F.2d 69 (1st Cir.1982). Pride does not dispute that it failed to provide respirators to its employees, and that its employees had access to the cited condition. However, Pride contends that (1) to prove that respiratory protection was "necessary to protect the health of the employee," as the cited standard requires, the Secretary must show that the cited condition involved "contaminated" air causing "occupational diseases," as the preceding subsection of the respiratory protection standard requires; (2) the standard is unenforceably vague in light of industry practice; (3) it had no knowledge of the violative condition; and (4) the violation was the result of unpreventable employee misconduct. A. Whether the secretary Proved the Requisite Health Hazard 1.What Health Hazard Must Be Established Section 1910.134(a)(2) requires the provision of respirators "when such equipment is necessary to protect the health of the employee." Pride argues that, in order to prove a violation of section 1910.134(a)(2), the Secretary must show, as the preceding subsection at 29 C.F.R. § 1910.134(a)(1) [[5 ]] requires, that the cited condition involved "occupational diseases" caused by breathing "contaminated" air. According to Pride, she has not met that burden in this case. Pride argues that, because subsection (a)(1) ends by referring to "the following requirements," it is necessary to read it together with subsection (a)(2) to learn what those requirements are. Pride contends that the Secretary failed to prove that Pride's employees were exposed to an "occupational disease" caused by "air contaminated with harmful,dusts, fogs, fumes, mists, gases, smokes, sprays, or vapors." The judge correctly ruled below that the requirements of subsection (a)(2) are to be read independently of subsection (a)(1).In Brock v City Oil Well Service Co. ("City"), 795 F.2d 507 (5th Cir. 1986), the employer had been cited for violating both sections 1910.134(a)(1) and (2) for failing to provide respirators to protect the health of employees on top of a "frac tank" against exposure to hydrogen sulfide gas ("H2S"), "a deadly byproduct of oil and gas production." 795 F.2d at 508 & n.1. The Fifth Circuit, to which this case can be appealed, [[6]] rejected City's argument that subsection (a)(1) required the Secretary to prove that engineering controls were not feasible before a requirement for respiratory protection arose under subsection (a)(2). More specifically, the court also rejected the argument that the language in subsection (a)(1) concerning the feasibility of engineering controls must be read into (a)(2), declaring that "the requirements of (a)(2) ... are independent of and can form the basis of a violation distinct from (a)(1)." 795 F.2d at 510 n. 5. Cf.Snyder Well Servicing, Inc., 10 BNA OSHC 1371, 1375-76, 1982 CCH OSHD ¶ 25,943, pp. 32,510-11 (No. 77-1334, 1982) (implicit rejection of employer's argument based on similar facts). Therefore,based on the decisions noted above, we reject Pride's argument that, before she can establish a violation of subsection (a)(2), the Secretary must show that Pride's employees were exposed to an "occupational disease" caused by "contaminated" air, as discussed in subsection (a)(1). 2. Whether the Secretary Has proven that Respirators Were "Necessary to protect the Health of the Employee" The next issue for consideration is whether the judge erred in finding that the Secretary established that respirators were "necessary to protect the health of the employee." In addressing the question of the need for respirators, the judge particularly relied on the testimony of the Secretary's Regional Industrial Hygienist Richard Wingo. Wingo testified that nitrogen displaces oxygen in a confined space and that when the oxygen falls below 19.5% of the air's content, the results can be: impairment of vision and mental capabilities; dizziness and fainting; unconsciousness; and even death. The judge found Wingo to he a "well-qualified individual" and an "impressive and highly credible witness." The judge stated that, when he viewed Wingo's testimony as a whole, "it is obvious that he considered the nitrogen, diesel and other elements to be a contaminant of the air in this confined space, causing an oxygen deficient atmosphere. Without question, I hold that view." (emphasis added; transcript reference deleted). The judge's finding that the atmosphere in the tank was oxygen-defficient is supported by his determination, which is not challenged by Pride, that "the credible evidence establishes that he [Reyes] fell and did not voluntarily enter the tank". The judge concluded that the employees assigned to monitor the returns from atop the tank, as well as those attempting to rescue, were exposed to "a hazard to the health (asphyxiation or drowning)." Pride has not introduced any evidence to dispute Wingo's testimony concerning the likelihood that the tank had an oxygen-deficient atmosphere on the day in question.[[7]] Based on that testimony by Wingo and the weight of the evidence establishing that Reyes did not voluntarily go into the tank, we conclude that Pride's employees were exposed to the hazard of asphyxiation, which resulted in their drowning. We therefore conclude that the judge did not err in finding that, in this case, respirators were "necessary to protect the health of the employee." B.Whether the standard is Unenforceably Vague Pride argues, as it did below, that section 1910.134(a)(2) is unenforceably vague because the standard's requirement for respiratory protective equipment is so broadly worded that it fails to provide notice sufficiently specific to satisfy due process concerns. When faced with such claims in relation to broadly-worded standards, the courts and the Commission have considered whether a reasonably prudent employer, familiar with the circumstances,would recognize a hazard warranting the same protection in the cited standard. See Bratton Corp., 14 BNA OSHC 1893, 1898-98,1990 CCH OSHD 29,152, p. 38,993 (No. 83-132, 1990) and cases cited therein. As Pride notes, for the generally- worded, personal protection standards at 29 C.F.R. §§ 1910.132(a) and 1926.28(a), the Fifth Circuit has determined that "industry custom and practice will generally establish the conduct of the reasonably prudent employer ......" Cotter & Co. v. OSHRC, 598 F.2d 911, 913 (5th Cir. 1979). Accord S & H Riggers & Erectors, Inc. v OSHRC, 659 F.2d 1273, 1285 (5th Cir. 198 1); Power Plant Div., Brown & Root, Inc. v. OSHRC, 590 F.2d 1363, 1365 (5th Cir. 1979); B & B Insulation, Inc. v. OSHRC, 583 F.2d 1364, 1370-71 (5th Cir. 1978). Pride notes that its supervisor Cantu and safety coordinator Jimmy Harville both testified that the common practice in the well-servicing industry is not to provide respirators, but rather to depend on the well operator or offer to provide respirators, as well as information about any dangerous condition concerning the well. This is because the well owners and operators have records on the well that are not available to well- servicing companies. Pride contends that, as it was not industry custom to provide respirators, section 1910.134(a)(2) is unenforceably vague. In his decision, the judge rejected Pride's argument, relying on the Fifth Circuit's decision in City, supra, where the court squarely rejected City's argument that the industry practice test that the Fifth Circuit itself had applied with regard to other standards (such as sections 1910.132(a) and 1926.28(a)) is appropriate for section 1910.134(a). The court stated that the employer's reliance on the same line of cases that Pride cites was "misplaced" because: The regulation here [section 1910.134(a)] is precise. In City's case, it concerns only one hazard and two remedies. The hazard is hydrogen sulfide . . . ; the two remedies are effective engineering controls and respirators, the requirements for the selection, use, and maintenance of which are set out in detail. See generaIly 29 C.F.R. § 1910.134. 795 F.2d at 511. The court noted that City's emphasis on the well-servicing industry's reliance on the well operator or owner to provide respirators was not only inappropriate under the cited standard, but also an improper attempt to "use industry custom to shift its statutory responsibility for the health and safety of its employees to third parties." Id. Based on the Fifth Circuit's decision in City, we find that the judge did not err in his ruling on this issue. Furthermore, we note that the Commission has issued a decision that relies on City and holds that section 1910.134(a)(2) is not vague, and therefore the reasonable employer test is not needed to interpret and apply the standard. Power Fuels, Inc., 14 BNA OSHC 2209, 2213, 1991 CCH OSHD ¶ 29,304, p. 39,346 (No. 85-166, 1991). We reject Pride's argument that the Fifth Circuit and Commission decisions are factually distinguishable from this case because those decisions involve the "well-known" hazard of H2S, instead of nitrogen. Section 1910.134(a)(2) does not make any reference to how well-known any specific substance or condition must be in order to require respirators. It states only that respirators must be provided where they are "necessary to protect the health of the employee." Nevertheless, we note that, as shown by Table 1 in the American National Standard, ANSI Z88.2-1969, Practices for Respiratory Protection, section 4 (1969),[[8]] oxygen deficiency in tanks or other confined spaces resulting from nitrogen or another simple asphyxiant diluting the oxygen in the air is a well-recognized respiratory hazard. Therefore, based on our own precedent and the decision in City by the Fifth Circuit, to which this case can be appealed, we reject Pride's arguments here and find, as the judge did, that section 1910.134(a)(2) is not unenforceably vague. C. Whether Pride Had Knowledge of the Violative Condition 1. Whether the Secretary Proved Knowledge As noted above, to prove a violation the Secretary must show that the cited employer had knowledge of the violative condition. She can satisfy this burden by establishing that the employer either knew, or, with the exercise of reasonable diligence, could have known of the presence of the violative condition. E.g., Tampa Shipyards, Inc., 15 BNA OSHC 1533, 1537, 1992 CCH OSHD ¶ 29,617, p. 40,100 (No. 86-360. 1992); Gary Concrete Prods., Inc., 15 BNA OSHC 1051, 1052, 1991 CCH OSHD ¶ 29,344, p. 39,449 (No. 86-1087, 1991). The actual or constructive knowledge of the employer's foreman or supervisor can be imputed to the employer. Id. The judge concluded that the Secretary made a pirma facie showing Pride's supervisor Cantu actually knew, or could have known, with the exercise of reasonable diligence, of the cited condition. He further found that Cantu's actual or constructive knowledge that respiratory equipment was necessary to protect the health of the employee was imputable to Pride. We find no error in the judge's ruling that a prima facie showing of Pride's knowledge has been established based on the record. As the judge noted, Cantu's actual knowledge of the conditions at the worksite that led to the violations cited here was established by Cantu's testimony that Perez complained to him that what was coming out of the tank was making [him] real dizzy" and "making [his] head hurt," and that he would not go back up on the tank. Cantu was given further notice of the hazard when he learned that Reyes and Zamora were in peril. Nevertheless, Cantu attempted to rescue them before almost being overcome himself. The Secretary also proved that Pride had constructive knowledge because its supervisor Cantu could have discovered and eliminated the hazard with the exercise of reasonable diligence. Reasonable diligence involves several factors, including an employer's "obligation to inspect the work area, to anticipate hazards to which employees may be exposed, and to take measures to prevent the occurrence." Frank Swidzinski Co., 9 BNA OSHC 1230, 1233, 1981 CCH OSHD 25,129, p. 31,032 (No. 76-4627, 1981). Although Cantu personally objected to Mostyn's instructions to put an employee on the tank, in light of the on-ground sampling method that Cantu had put in place, Cantu did not raise the matter at that time with his supervisors at Pride. However, he testified that he had previously raised with them other orders from Mostyn. Moreover, Cantu admitted that, even though he could not have done anything that Mostyn had not approved, the safety of Pride's crew was his own responsibility. As a crew supervisor, Cantu had a general responsibility to acquaint himself with the contents of the tank and the hazards that they might pose to Pride employees. This obligation was heightened when Perez complained to him that what was coming out of the well was "making [him] real dizzy" and "making [his] head hurt." In light of Perez's complaint and the considerable likelihood of serious injury, Cantu could have at least told Mostyn or his supervisor at Pride about Perez's complaint and made inquiries. See Getty Oil Co. v. OSHRC, 530 F.2d 1143, 1146 (5th Cir. 1976) (reasonable diligence includes "simple expediency of ... making inquiry"). Evidence in the record indicates that Cantu knew that nitrogen was being used to force the material out of the well, and that nitrogen and diesel were present in the tank. He said as much to Perez in response to Perez's question following his complaint of dizziness and a headache. Furthermore, Cantu had some understanding that the operations on the day of the accident were not typical. He testified that, based on his fifteen years of experience in the oil well business, the contents of the well were not ordinarily put into an enclosed "frac tank" when nitrogen was being used. Cantu stated that when the operation involves jetting nitrogen, the returns from the well are usually directed into an "open earth pit" or an "open 200 barrel, tank." Arguably, a reasonably diligent employer who was aware of this departure from normal procedures would have questioned Mostyn or the well operator after Perez complained, if not before. Other factors indicative of reasonable diligence include adequate supervision of employees, and the formulation and implementation of adequate training programs and work rules to ensure that work is safe. Gary Concrete, 15 BNA OSHC at 1054-55, 1991 CCH OSHD at p. 39,451-52; see Towne Constr Co., 12 BNA OSHC 2185, 2190- 91, 1986-87 CCH OSHD ¶ 27,760. pp. 36,312-13 (No. 83-1262, 1986), aff'd, 847 F.2d 1187 (6th Cir. 1988). Although the record here shows instances where Cantu's supervision of his crew was arguably not adequate, the real problem was that Pride had failed to formulate and implement adequate work rules and training programs to ensure that Cantu had been informed of the appropriate safety considerations. Cantu testified that he had not been trained in what do in oxygen-deficient atmospheres, and, based on the evidence concerning the accident day, apparently neither had any of his crew. However, he and his crew had been made aware of the dangers of H2S and trained in how to respond to it, including how to use masks and oxygen tanks. Cantu's lack of understanding of the oxygen deficiency in the tank was most dramatically demonstrated when he went in the tank himself in the rescue attempt. Based on the considerations above, we conclude, as the judge did, that the Secretary has made her prima facie showing that Pride had knowledge of the violative condition. 2. Whether Pride Rebutted the Showing of Knowledge To rebut prima facie proof that the knowledge of a supervisor should be imputed to it, the cited employer must offer evidence that it had: established work rules designed to prevent the violation; adequately communicated those work rules to its employees (including supervisors); taken reasonable steps to discover violations of those work rules; and effectively enforced those work rules when they were violated. E.g., Tampa Shipyards, Inc., 15 BNA OSHC at 1538,1992 CCH OSHD at p. 40,100; A.P. O'Horo Co., 14 BNA OSHC 2004, 2007-08, 1991 CCH OSHD ¶ 29,223, p. 39,129 (No. 85-369, 1991). There is no evidence that Pride had a work rule specifically addressing the hazards of oxygen-deficient atmospheres. Rather, Pride relies on its work rule for confined space entry under the theory that an employee sticking his head through the opening in the top of the tank to observe the level of the "returns" would be violating that rule, as would an employee who entered the tank for rescue purposes. Pride contends that whatever knowledge Cantu might have had of the violative condition cannot be imputed to it because it had implemented, communicated, and enforced the following "basic safety rule" set forth in its "Employee Benefit Summary and Safety Guide:" Confined Spaces -- Employees are not authorized to enter any confined spaces for any reason. Confined spaces are defined as frac tanks, storage tanks, tank hatches or any other spaces not fully ventilated to fresh air. We note that supervisor Cantu's voluntary entry into the tank in his attempt to rescue his crew members was in clear violation of this work rule. Where a supervisor engages in misconduct and is exposed to the hazardous condition, that is strong evidence of lax enforcement of the employer's safety program. E.g., Brock v. L.E. Myers Co., 818 F.2d 1270, 1277 (6th Cir. 1987), cert. denied, 484 U.S. 989 (1987); Baytown Constr. Co., 15 BNA OSHC 1705, 1710, 1992 CCH OSHD ¶ 29,741, p. 40,414 (No. 88-2912-S, 1992). Pride could have prevented this conduct by sufficiently training Cantu in the hazards of, and procedures necessary for, oxygen-deficient atmospheres. However, Cantu testified that Pride failed to provide this type of training, and Pride presented no evidence that it had given such training. See Daniel Constr Co., 10 BNA OSHC 1549,1552, 1982 CCH OSHD ¶ 26,027, p. 32,672 (No. 16265, 1982). As Cantu's testimony indicated, nitrogen is not uncommonly used in the well-servicing industry, and its diluting effect on oxygen should have been made known to all employees, especially supervisors. The Act places final responsibility for compliance with its requirements on the employer. E.g., City, 795 F.2d at 511, quoting section 5(a)(2) of the Act, 29 U.S.C. ¶ 654(a)(2) ("[e]ach employer ...shall comply" with OSHA standards) (court's emphasis). An employer who has failed to address a hazard by implementing and enforcing an effective work rule cannot shift to its employees the responsibility for assuring safe working procedures. See, e.g., Stuttgart Machine Works, Inc., 9 BNA OSHC 1366, 1369, 1981 CCH OSHD ¶ 25,216, p. 31,142 (No. 77-3021, 1981). An employer "cannot fail to properly train and supervise its employees and then hide behind its lack of knowledge of their dangerous working practices." Danco Constr. Co. v. OSHRC, 586 F.2d 1243, 1247 (8th Cir. 1978). Here, Pride failed to adequately train its supervisor in the respiratory hazard of, and the safety procedures for, oxygen deficiency, to which he and some of his crew were exposed. We therefore conclude that Pride has failed to rebut the Secretary's showing, and we impute Cantu's knowledge to Pride. D. Whether the Conduct of Pride's Employees Was Unpreventable Pride further asserts that it was not in violation of the standard because it did all that it could reasonably have done to prevent the violation. To prove the affirmative defense of unpreventable employee misconduct, the employer must show that it had established a work rule designed to prevent the violation, adequately communicated those work rules to its employees (including supervisors); taken reasonable steps to discover violations of those work rules; and effectively enforced those work rules when they were violated. See, e.g., Marson Corp., 10 BNA OSHC 1660, 1662, 1982 CCH OSHD ¶ 26,075, p. 32,804 (No. 78-3491, 1982). In the preceding section, we discussed whether Pride established that the conduct of its supervisory employee Cantu was unpreventable, which is necessary to rebut the Secretary's showing of knowledge imputed to from Cantu. We concluded that Pride did not prove that Cantu's conduct was unpreventable and therefore did not rebut the Secretary's proof of knowledge. With regard to whether the conduct of its non-supervisory employees Reyes and Zamora was unpreventable, Pride introduced into evidence the pages that these two employees had signed acknowledging receipt of the safety guide in August 1986, and "agree[ing] to read all safety instructions pertinent to [their] jobs." With regard to Reyes, the work rule upon which Pride relies did not address the hazardous condition to which he was exposed when he was working atop the tank. As the judge found, based on the autopsy report and testimony, the multiple abrasions and contusions on the upper front of Reyes' head showed that he had not entered the tank voluntarily. The judge noted that under the work rule, employees "could very well conclude" that they did not violate the work rule by merely sticking their heads in the hole at the top of the tank to see the level of the returns inside the tank. Moreover, when specifically directed by a supervisor, as Reyes was by Cantu here, to perform work that could possibly cause the employee to break a safety rule, the employee could reasonably consider the supervisor's instructions as overriding the safety rule. Cf. Regina Constr. Co., 15 BNA OSHC 1044, 1048, 1991 CCH OSHD 29,354, p. 39,468 (No. 87-1309, 1991) (employee could not be in a hazardous location but for supervisor's orders). With regard to Zamora, Cantu's testimony as to what another employee told him demonstrates that Zamora attempted to rescue Reyes and therefore could also have entered the tank voluntarily. If this had been the case, Zamora also would have been in violation of the work rule. Nevertheless, the evidence also shows that Cantu, Zamora's supervisor, was not only failing to enforce the rule, but he was breaking it himself. Furthermore, it is arguable that the work rule does not really address the condition that Cantu and Zamora faced--the necessity for an emergency rescue. As the Secretary notes, rescue attempts are readily foreseeable in the oil well servicing industry, yet Pride had no work rule addressing them.[[9]] Just as Pride failed to adequately train its supervisor Cantu and now seeks to hide behind his lack of knowledge of the hazard, so does it also attempt to hide behind Reyes and Zamora's lack of training and supervision. As discussed above, this is not permission. See Danco, 586 F.2d at 1247. Therefore, we reject Pride's contentions that the conduct of Reyes and Zamora was unpreventable. E. Summary and Penalty Based on our findings above, we conclude that the judge did not err in determining that Pride committed a violation of section 1910.134(a)(2). The judge found that the violation was serious under section 17(k) of the Act, 29 U.S.C. § 666(k), as alleged. Pride does not challenge that characterization on review. We therefore conclude that the violation was serious. The judge assessed the proposed penalty of $560 for this violation. In light of the penalty factors in section 17(j) of the Act, 29 U.S.C. § 666(j), especially the gravity of the violation, and the immediate, direct relief from the hazardous atmosphere that respirators could have provided, we assess a penalty of $1,000. Ill. Caution Sign The judge affirmed citation no. 1, item 3, as amended, which alleges a serious violation of 29 C.F.R. § 1910.145(c)(2)(i). [[10]] It was undisputed that there was no caution sign warning employees against the potential hazards involved in monitoring the returns from the opening in the top of the tank or entering the tank for emergency rescue. The compliance officer testified that such signs could have caused employees to exercise the necessary caution in light of the potential hazard. Pride's supervisor Cantu testified that over the years he had seen "frac tanks" with signs on them saying things like: ."poisonous gas, do not enter." Pride contends that, because it did not own the tank, but rather only leased it, it was not responsible for providing a caution sign. As noted above, the Fifth Circuit stated in City that an employer "cannot shift its statutory responsibility for the health and safety of its employees to third parties." 795 F.2d at 511. Moreover, from a practical standpoint, there is no requirement that the sign be permanent. Nor does the sign need to be attached to the tank itself, but rather can be, as Cantu testified he had seen, "'anywhere around it" that would be visible to employees. Pride also contends that it had taken sufficient measures to warn employees by its safety manual. However, as discussed above, the work rule against entering confined spaces, even assuming it implements the requirements of the cited standard, was not enforced. Pride also argues that it did not know the contents of the atmosphere within the tank and therefore would have had no way of knowing whether warning signs were needed. We reject that contention. As the discussions in the sections above show, Pride did not take sufficient measures to either warn or train its employees, and it is now trying to hide behind the resultant lack of knowledge on its employees' part regarding the possibility of oxygen deficiency. Based on the considerations above, including the well-documented hazards in the record, [[11]] and Pride's knowledge of them, we conclude that the judge did not err in finding that Pride violated section 1910.145(c)(2)(i). Pride does not challenge on review the serious characterization of this violation. Accordingly, we affirm the violation as serious. The judge assessed the proposed penalty of $560. Based on the penalty factors in section 17(j) of the Act, 29 U.S.C. § 666(j), we assess a more appropriate penalty of $200. IV. Order For the reasons stated above. we affirm the decision of Judge Botkin and find no error in his conclusions that Pride committed serious violations of sections 1910.134(a)(2) and 1910. 145(c)(2)(l). We assess respective penalties of $ 1,000 and $200 for these violations. Edwin G. Foulke, Jr. Chairman Donald G. Wiseman Commissioner Velma Montoya Commissioner Dated: August 17, 1992 ------------------------------------------------------------------------ FOOTNOTES: [[1]] The judge characterized this testimony by Perez as "direct and persuasive." (Throughout his decision, he referred to this employee as "Mario" because he mistakenly stated that, instead of Perez (as the employee spelled his own name at the hearing), his last name was Reyes, the last name of another Pride employee.) The judge specifically credited Perez's testimony over Cantu's testimony that he saw Perez walk over and lean down near the opening, as if to listen. We defer to the judge's credibility determination. See, eg., C. Kaufman, Inc., 6 BNA OSHC 1295,1297, 1977- 78 CCH OSHD 22,481, p.27,099 (No.14249,1978). [[2]] Cantu testified that he told his crew to "stand up" while monitoring the returns. The judge specifically discredited that statement due to its inconsistency with Cantu's earlier testimony that he did not know what instructions Reyes had received,even though Cantu was the one who had given him the order to relieve Perez. Based on our review of the record, we see no need to disturb the judge's evaluation of these parts of Cantu's testimony. Moreover, even if Cantu had given instructions to stand up, he was put on notice that they were not being followed when, as he testified, he observed Reyes sitting near the opening. [[3]] The Secretary also alleged a serious violation of 29 C.F.R. 1910.23(a)(6). which requires that a "manhole floor opening" shall be constantly attended when the cover is not in place.The judge vacated this item. The Secretary does not challenge that ruling on review, and we do not consider it here. [[4]] The standard Provides: § 1910-134 Respiratory protection. (a)Permissable practice. . . . . (2) Respirators shall he provided by the employer when such equipment is necessary to protect the health of the employee. The employer shall provide the respirators which are applicable and suitable for the purpose intended. The employer shall be responsible for the "establishment and maintenance of a respiratory protective program which shall include the requirement outlined in paragraph (b) of this section. [[5]] Section1910.134(a)(1)provides In the control of those occupational diseases caused by breathing air contaminated with harmful dusts, fogs, fumes, mists, gases, smokes, sprays, or vapors, the primary objective shall be to prevent atmospheric contamination. This shall be accomplished as far as feasible by accepted engineering control measures .... When effective engineering controls are not feasible,or while they are being instituted,appropriate respirators shall be used pursuant to the following requirements. (Emphases added.) [[6]] This case can be appealed to the Fifth Circuit based on the locations of the alleged violation and the principal office of the employer. See sections 11(a) and (b) of the Act, 29 U.S.C. § 660(a) and (b). [[7]] Pride has not acknowledged that the atmosphere in the tank was oxygen- deficient. It suggests that the Secretary must show the percentage oxygen in the atmosphere, which Pride notes she has failed to do. However,as the judge stated in his decision, it was not necessary for the Secretary to establish the percentage of oxygen in order to prove the hazard of oxygen deficiency existed. He additionally noted that, despite Pride's successful objection to the Secretary's introduction of atmospheric testing results into the record. Pride itself introduced a statement as to the results into evidence in one of its own exhibits. We further note that the conditions at the well on the day before the accident, when nitrogen was not being inserted into the tank, are not relevant to the citation items before us. [[8]] This ANSI standard was the source of OSHA's respiratory protection standard at section 1910.134. See 29 C.F.R. § 1910.139. [[9]] Pride does not have any general safety rules on rescues from tanks or wells. Included in its work rules concerning H2S is only the admonition: Rescuers must exercise due caution." [[10]] "The standard provides: § 1910.145 Specifications for accident prevention signs and tags. (a) Scope. (1) These specifications apply to the ...use of signs...intended to indicate...specific hazards of a nature such that failure to designate them may lead to accidental injury to workers.... (c) Classification of signs according to use-- . . . . (2) Caution signs. (i) Caution signs shall be used only to warn against potential hazards or to caution against unsafe practices. (Emphases added.) [[11]] In light of the oxygen-deficient atmosphere in the tank, which we found above, a "danger sign" (as discussed in 29 C.F.R {sym} 1910.145(c)(l)) may have been appropriate to warn of the specific danger of asphyxiation to which employees were exposed while observing the level of the returns through the opening in the tank's top.