Fairfax County Board Chairman John F. Herrity, in apparent violation of the county's public disclosure law, cast three favorable votes for developers in the last 13 months without disclosing that he had received contributions for his 1983 campaign from those developers or their associates.

According to county records, Herrity also failed to disclose his receipt of a political donation before the Board of Supervisors voted in January for a local firm's request for $8 million in industrial revenue bonds.

Fairfax County law requires supervisors, before participating in a land use issue or a request for tax-exempt government bonds, to disclose publicly "to the best of their knowledge" whether, during the preceding five years, they received a gift or donation exceeding $50 from anyone with a financial interest in the application. After disclosure, the supervisors may vote on the application.

Herrity did not return repeated telephone calls yesterday.

In a related matter, Fairfax Commonwealth's Attorney Robert F. Horan Jr. is investigating whether Herrity violated state or county public disclosure laws when he failed to report his joint ownership of an office condominium unit with the principals in Hersand Builders Inc. Herrity participated in the board's consideration of a major rezoning that authorized Hersand to build a 137-unit town house project in the Springfield district.

Herrity voted against the rezoning application but then supported a motion granting Hersand several waivers to county zoning regulations.

According to county records, Herrity voted May 20, 1985, for an application to renew an exemption from county height restrictions for the developers of an office park and hotel near the Dulles International Airport. Before voting, Herrity did not disclose his receipt of a $200 campaign donation in 1983 from Herbert N. Morgan, a partner in the Webb Sequoia Co., an owner of the development site, the records show.

Those records also show that Herrity failed to disclose the contribution from Morgan on March 10 when he voted for Dulles Corner Associates' request for an additional waiver of county height restrictions for the office park and hotel project.

In another rezoning case, taken up by the board Oct. 21, Herrity did not disclose that he received a 1983 campaign donation from John P. DiGiulian, an officer of the Hallmark Bank and Trust Company of Virginia. During that meeting, Herrity voted in favor of Hallmark's application for a zoning waiver for a drive-in bank in the Lee district.

According to campaign finance reports on file in the county registrar's office, DiGiulian made a $250 donation to Herrity's successful 1983 reelection drive.

On Jan. 6, Herrity voted to allow $8.03 million in industrial revenue bonds to be issued to Artillery Hill Limited Partnership for the acquisition of property and the construction of a computer facility at Rte. 28 and Fort Drive in the Springfield District. Prior to voting, Herrity failed to disclose his 1983 contribution from Morgan, who also is a general partner in the Artillery Hill project.

In compliance with county law, the applicants in the four projects listed Morgan and DiGiulian and their titles on the affidavits that must accompany such applications. It is then up to board members, before considering the requests, to disclose whether they have had a financial relationship with those involved in the projects or have received a donation in excess of $50.

Before both votes on Dulles Corner Associates' office park project, Supervisors Nancy K. Falck (R-Dranesville) and T. Farrell Egge (R-Mount Vernon) reported that they had received 1983 campaign contributions from the developers or their associates.

Egge also disclosed a contribution he had received from DiGiulian before the board considered the Hallmark Bank project last October. Falck and Egge also disclosed contributions they had received from associates in the Artillery Hill partnership before voting on its $8 million bond request earlier this year.