Decedent was a volunteer fireman in the Pleasantville Fire District. The chief of the Pleasantville Fire District had accepted an invitation to participate in an exhibition fire drill and parade at Chappaqua, New York, on August 27, 1948. The volunteer firemen were directed to participate. There is evidence that they were compelled to do so or be subject to a fine. Decedent's regular duties were that of postal clerk in the Pleasantville Post Office. Pursuant to direction, he went to Chappaqua upon a vehicle of the Pleasantville Fire Department, and participated in the parade as a member of the fire department band, and played a snare drum in the parade. It was an unusually hot evening. Decedent was afflicted with obesity. He had a previously existing heart condition which was not disabling. Shortly after participating in the parade decedent collapsed, and died in a hospital four days later. The board has found that unusual exertion and strain, superimposed on the underlying cardiac condition, aggravated that condition and caused his death. While there is conflicting medical testimony, there is substantial evidence to sustain the findings of the board. Appellants also assert that if the award is sustained, it should be against the Chappaqua Fire District and the Hartford Accident and Indemnity Company, its carrier, pursuant to section 10 Work. Comp. of the Workmen's Compensation Law. The board in its decision has held that decedent was not responding to a "call for assistance" from the Chappaqua Fire District, within the meaning of section 10 Work. Comp. of the Workmen's Compensation Law. We think the interpretation of the board is correct. There was no fire or other public emergency. The acceptance of the invitation to parade by the chief of the Pleasantville Fire Department was purely voluntary. We think that a fair, realistic construction of the word "assistance" and the words "call for assistance" does not include voluntary participation in a parade. Award unanimously affirmed, with one bill of costs to be divided equally between the respondents, Chappaqua Fire District and Hartford Accident Indemnity Company, and the Workmen's Compensation Board, with disbursements to each.