In a 1991 decision of the former Workers’ Compensation Commission, United Engineers & Constructors was permitted to offset its obligation to pay weekly workers’ compensation benefits to its employee, Norman LaPointe, by the payments that LaPointe received pursuant to a Massachusetts decree. After LaPointe obtained a lump-sum settlement of his claim against his Massachusetts employer, the Workers’ Compensation Board granted LaPointe’s petition for an order of payment, ruling that United Engineers was no longer entitled to the offset and must reinstate weekly benefits. Because we agree with the employer that the Board misconstrued the 1991 decision of the Commission, we vacate the decision of the Board.1
In August 1986 Norman LaPointe injured his back while working for United Engineers. LaPointe suffered a subsequent work-related back injury in February 1989 while employed in Massachusetts by Wormald Fire Systems and was awarded short-term total and ongoing partial incapacity benefits for that injury pursuant to Massachusetts workers’ compensation law. In 1991 the Maine Commission granted LaPointe’s petition for restoration, concluding that his 1986 injury was “a substantial contributing factor” to his ongoing incapacity. The Commission ordered United Engineers to pay short-term total and ongoing partial incapacity benefits, but also concluded that United Engineers was entitled to “receive a week by week setoff for benefits paid to the Employee under Massachusetts law for his various periods of incapacity.” Because the Massachusetts award exceeded United Engineers’ weekly benefit payments, the employer set off its entire weekly benefit obligation. The Commission’s 1991 decision was not appealed.
In May 1992 LaPointe entered into a lump-sum settlement of his Massachusetts claim for ongoing partial incapacity benefits in the amount of $100,000, with an additional $25,000 for attorney fees. The settlement did not include payment for permanent im*460pairment or medical expenses. In June 1992 LaPointe filed a petition for an order of payment against United Engineers seeking payment of his ongoing partial incapacity benefits. He claimed that United Engineers was no longer entitled to a week-by-week setoff because the Massachusetts claim had been paid in a lump sum. In October 1994 the Board granted LaPointe’s petition and ordered the employer to reinstate continuing partial benefits. The Board interpreted the 1991 setoff as conditional on the continuation of weekly payments from the Massachusetts employer, and concluded that “once payments stopped from Massachusetts, for any reason, the employer’s setoff also necessarily ended.” The Board denied United Engineers’ motion for findings of fact, and we granted the employer’s petition for appellate review pursuant to 39 M.R.S.A. § 103-C (1989).
United Engineers contends that the setoff awarded in 1991 was not conditional on the continuation of weekly benefit payments from the Massachusetts employer, and therefore it is entitled to set off the entire amount of LaPointe’s Massachusetts settlement against its continuing obligation to pay weekly incapacity benefits. LaPointe contends, however, that a hearing officer’s interpretation of a Commission decision must be affirmed on appeal if supported by competent evidence. The hearing officer’s interpretation of the 1991 decision was a conclusion of law, not a finding of fact. This is not a case in which the Board relied on extrinsic evidence to aid in the interpretation of ambiguous language in a prior decision. Moreover, despite the deference we accord to an administrative agency’s application of its statute, the Board’s interpretation of the 1991 decision is incorrect.
The Board gave controlling weight to the fact that the 1991 decision awarded a “week by week setoff.” A “week by week setoff for benefits paid” is not the same as a setoff “for benefits paid week by week.” In the first instance, the phrase “week by week” is intended to modify the setoff; in the latter instance the phrase is intended to describe the benefits that may be set off. The 1991 decision did not award a setoff “for benefits paid week by week,” language that might have supported the Board’s conclusion that the decision was conditional on the payment of weekly, as opposed to lump-sum, benefits. In this case, however, United Engineers was awarded a “week by week setoff’ that corresponded to its duty to pay week by week benefits. There is nothing in the language of the 1991 decision to support the conclusion that the setoff was contingent on the payment of weekly benefits, as opposed to lump-sum benefits, by the Massachusetts employer.
Moreover, it is widely recognized that an employer is entitled to a credit for a duplicate recovery in a different state. Thomas v. Washington Gas Light Co., 448 U.S. 261, 281, 100 S.Ct. 2647, 2660-61, 65 L.Ed.2d 757 (1979); de Cancino v. Eastern Air Lines, 239 So.2d 15, 17 (Fla.1970); Lavoie’s Case, 334 Mass. 403, 135 N.E.2d 750, 751 (1956); Stanley v. Hinchliffe & Kenner, 395 Mich. 645, 238 N.W.2d 13, 17-19 (1976); Hernandez v. G & P Gonstr. Co., 43 A.D.2d 228, 350 N.Y.S.2d 808, 811 (1974); Restatement of Conflict of Laws § 403 (1934); 4 A. Larson, The Law of Workmen’s Compensation § 85 (1993). See also Van Houten v. Harco Constr., Inc., 655 A.2d 331, 332 (Me.1995) (parties voluntarily agreed to credit benefits from one state against the other); LeBlanc v. United Eng’rs & Constructors Inc., 584 A.2d 675, 677 (Me.1991) (commission authorized employer to credit payments made pursuant to New Hampshire law); Dissell v. Trans World Airlines, 511 A.2d 441, 442 (Me.1986) (commission awarded credit for payments made pursuant to Massachusetts claim). A primary purpose for the setoff is to prevent the employee from receiving a double recovery.
The Commission concluded in 1991 that LaPointe’s Maine and Massachusetts injuries combined to create a single incapacitating condition. Because no claim was brought against LaPointe’s Massachusetts employer pursuant to the Maine Act, the Commission awarded total benefits against United Engineers for the combination of his injuries. See Brackett v. A.C. Lawrence Leather Co., 559 A.2d 776, 777-78 (Me.1989) (employer may be fully liable for employee’s incapacity *461that results from combination of work injury and subsequent nonwork-related injury). Because LaPointe was receiving benefits pursuant to Massachusetts law for the combined effects of his Massachusetts and Maine injuries, the Commission awarded United Engineers a setoff to prevent a double recovery. As the Massachusetts Supreme Judicial Court has stated: “All compensation acts rest upon the policy that the industry should bear the burden of industrial accidents, but there is no policy that justifies placing the burden on the industry twice, especially where that results in paying the employee so much that it becomes to his advantage to remain away from work.” Mizrahi’s Case, 320 Mass. 738, 71 N.E.2d 383, 385 (1947).
LaPointe contends that the Board’s interpretation of the Commission decision is the only permissible interpretation, citing Kennedy v. Brunswick Convalescent Ctr., 584 A.2d 678, 680 (Me.1991), and Harding v. Sheridan D. Smith, Inc., 647 A.2d 1193, 1194 (Me. 1994). Both cases are distinguishable. In Kennedy, we decided that an insurer liable for a subsequent injury could not receive an apportionment against an insurer who had previously settled the employee’s claim for an earlier injury. In Harding, we decided that an employer paying benefits for a prior injury was not entitled to an apportionment against an employee who suffered a subsequent aggravating injury while self-employed and not covered by the Act. Both cases involved an interpretation of the apportionment statute, 39 M.R.S.A. § 104-B (1987), repealed and replaced by P.L.1991, eh. 885, §§ A-7, A-8 (effective January 1,1993), codified as 39-A M.R.S.A. § 354 (Supp.1995).
The credit awarded in the 1991 decision was not an apportionment. An apportionment would have divided liability between two employers according to their relative contribution to an incapacitating condition. In this case, because there was no claim against the Massachusetts employer pursuant to the Maine law, the Commission ruled that United Engineers was fully liable for LaPointe’s incapacity. The setoff awarded in the 1991 decision was a credit against duplicate recoveries received pursuant to two separate workers’ compensation systems.
We agree therefore with United Engineers that, pursuant to the 1991 decision, it is entitled to set off the Massachusetts lump-sum settlement against its continuing obligation to pay weekly benefits. We do not agree, however, with its contention that the Massachusetts recovery may be applied against its obligation to pay permanent impairment or attorney fees. We have held that, because permanent impairment and incapacity benefits are designed to compensate employees for different types of loss, they are not duplicative. See Delorge v. NKL Tanning, Inc., 578 A.2d 1173, 1174 (Me.1990). We have also held that employers are not entitled to set off incapacity benefits received pursuant to the federal Longshore and Harborworkers’ Compensation Act against an obligation to pay permanent impairment benefits pursuant to the Maine Act. Bouford v. Bath Iron Works Corp., 514 A.2d 470, 474 (Me.1986), cert. denied, 479 U.S. 1065, 107 S.Ct. 951, 93 L.Ed.2d 1000 (1987).2 Our rationale in that case applies equally when the setoff is against a recovery awarded in another state.
Similarly, attorney fees and incapacity benefits are not duplicative. Attorney fees are a necessary cost of prosecuting a workers’ compensation claim and are not generally treated as a “benefit” for purposes of the Act. See Campbell v. School Admin. Dist. No. 59, 658 A.2d 1094, 1097 (Me.1995) (fees are not a benefit for purposes of section 68); Lucas v. E.A Buschmann, Inc., 656 A.2d 1193, 1195 (Me.1995) (fees are not a benefit for purposes of penalizing employer for nonpayment during appeal period).
*462Accordingly, we conclude that, pursuant to the 1991 Commission decision, United Engineers is entitled to set off its obligation to pay weekly incapacity benefits by the amount of the lump-sum settlement of LaPointe’s Massachusetts claim, excluding fees. United Engineers is not permitted to apply that settlement payment against its obligation to pay permanent impairment benefits or attorney fees.
The entry is:
Decision vacated. Remanded to the Workers’ Compensation Board for further proceedings consistent with the opinion herein.
WATHEN, C.J., and CLIFFORD, RUDMAN, DANA, and LIPEZ, JJ., concurring.. Because LaPointe’s petition for forfeiture was filed in 1992, the proceeding was pending on the effective date of title 39-A and the issues in this appeal are governed exclusively by former tide 39. Riley v. Bath Iron Works Corp., 639 A.2d 626, 627-29 (Me.1994).
. Until 1991, permanent impairment and incapacity benefits could be received concurrently. 39 M.R.S.A. § 56-B (1989); Campbell v. Bates Fabrics, Inc., 422 A.2d 1014, 1015 n. 5 (Me. 1980). In 1991, in an effort to scale back permanent impairment recoveries, the Legislature amended section 56-B to allow incapacity benefits to be offset against benefits for permanent impairment. P.L.1991, ch. 615, § D-8. This amendment expressly applies only to injuries occurring on or after October 17, 1991, and therefore does not apply to either of LaPointe's injuries. P.L.1991, ch. 615, § D-26.