Opinion by
Judge MacPhail,Frank Martincic (Claimant) appeals an order of the Workmens Compensation Appeal Board (Board) which amended a referees decision to award benefits only from the date notice of disability was given to Claimants employer, rather than from the date of disability. We vacate and remand.
Claimant worked as a stationary engineer for more than thirty years, the last thirteen of which was in the employ of the Greater Pittsburgh International Airport. His job entailed maintaining and repairing heating and air conditioning equipment in an airport terminal, which exposed Claimant to asbestos dust and fumes. Claimant retired on August 25, 1978 because he had trouble breathing and “getting around.”1
*240In November of 1981, Claimant was examined by Dr. C. Vaughn Strimlan who informed the Claimant that he had asbestosis. Claimant subsequently consulted an attorney and on January 11, 1982, two letters were sent to Claimants employer informing it that Claimant is “totally and permanently disabled as a result of a presumed occupationally-related pulmonary disease.”2
Claimant filed a claim petition for workmens compensation benefits on April 26, 1982, alleging that he became totally disabled as a result of asbestosis on August 25, 1978. The petition was assigned to a referee for a hearing, and on October 12, 1984, the referee awarded benefits from October 26, 1978, the date of Claimants first disability.3 The Board amended the referees decision so that compensation commenced on January 12, 1982, the date on which Claimants employer received notice of the disability. Claimants petition for review of this order is now before our Court.
Claimants sole argument on appeal is that the Board incorrectly amended the referees order to award benefits from the date of notice of disability rather than from the date of disability. Our review of the Boards order is, of course, limited to a determination of whether constitutional rights have been violated, an error of law committed, or whether its findings are not supported by substantial evidence. Section 704 of the Administrative Agency Law, 2 Pa. C. S. §704.
*241Section 311 of The Pennsylvania Workmens Compensation Act, (Act)4 77 P.S. §631, provides:
Unless the employer shall have knowledge of the occurrence of the injury, or unless the employe or someone in his behalf, or some of the dependents or someone in their behalf, shall give notice thereof to the employer within twenty-one days after the injury, no compensation shall be due until such notice be given, and, unless such notice be given within one hundred and twenty days after the occurrence of the injury, no compensation shall be allowed. However, in cases of injury resulting from, ionizing radiation or any other cause in which the nature of the injury or its relationship to the employment is not known to the employe, the time for giving notice shall not begin to run until the employe knows, or by the exercise of reasonable diligence should know, of the existence of the injury and its possible relationship to his employment. The term ‘injury’ in this section means, in cases of occupational disease, disability resulting from occupational disease. (Emphasis added.)
In interpreting Section 311 of the Act, our Court has held that:
When there is evidence in the record that Claimant, if he had exercised reasonable diligence, may have acquired such knowledge from which a referee could find that Claimant should have known of his disability from an occupational disease and its causal relationship to his employment, a finding by the referee of when Claimant should have known these matters is necessary for our review.
*242Arcadia Coal Co. v. Workmen's Compensation Appeal Board (Kubalic), 79 Pa. Commonwealth Ct. 148, 152-153, 468 A.2d 906, 908 (1983) (emphasis in original).
This critical finding is required because under the provisions of Section 311, where the claimant gives notice of his disability from disease within 21 days of the date he knew or should have known of the injury and its relationship to his employment, compensation is payable from the date of disability. If, however, the claimant gives notice after the 21 days has elapsed but within 120 days of the date he knew or should have known of his injury, compensation is then payable from the date that notice was given. See Culp Industrial Insulation v. Workmen's Compensation Appeal Board, 57 Pa. Commonwealth Ct. 599, 426 A.2d 1263 (1981).
In the case now before us the referees sole finding of fact regarding notice reads as follows:
10. Notice was sent to the defendant (employer) by certified mail dated January 12, 1982 and January 13, 1982. Your Referee finds this Notice to be timely as the claimant was not told that he had asbestosis until he met with his counsel and was advised of the contents of Dr. Strimlans letter of January 12, 1982.
The Board, citing Arcadia Coal Co., correctly concluded that that finding was insufficient to satisfy the requirement that there be a specific finding as to when the Claimant knew or should have known of his disability and its relationship to his employment. Then, however, the Board, without taking additional evidence, proceeded to state that January 12, 1982 was “the date the claimant knew or should have known of a causal relationship between his employment and work-related injury.”
Our case law is to the effect that since the 1972 amendments to the Act, when the Board hears no addi*243tional evidence, it may not “make its own findings of fact, but is limited to reviewing conclusions of law and to determining whether the findings of fact of the referee are supported by competent evidence.” Pages Department Store v. Velardi, 464 Pa. 276, 282-283, 346 A.2d 556, 559 (1975).
Inasmuch as there has been no finding by the factfinder as to when the Claimant knew or should have known of his injury and its relationship to his employment, we are unable to resolve the issue presented to us of whether compensation is payable from the date of disability or the date notice of disability was given. We, therefore, must remand the case to the Board for further remand to the referee for the necessary factfinding.
Order
The order of the Workmens Compensation Appeal Board in the above-captioned proceeding is vacated, and the matter is remanded for further remand to the referee for findings consistent with the foregoing opinion.
Jurisdiction relinquished.
Notes of Testimony (N.T.) from October 18, 1982 at 13.
A letter addressed to the Law Department of the County of Allegheny was received on January 12, 1982, and one addressed to the employers Administrative Offices was received January 13, 1982. See N.T. at 18-19; Claimants Exhibits 2 and 3.
The Claimant appears to have retired on August 25, 1978 although the referee found his last day of work to be October 25, 1978.
Act of June 2, 1915, P.L. 736, as amended.