After months of campaigning by the Service Employees International Union (SEIU), more than 4,700 janitors who work for four of the five largest cleaning companies in Houston agreed to unionize. The decision was certified late Tuesday by the American Arbitration Association.

The majority of janitors who work for GCA Services Group, as well as ABM Janitorial Services, Sanitors Inc. and OneSource Facility Services agreed to form a union with the SEIU. According to officials, Pritchard Industries Southwest tentatively agreed to also join the union, but their decision is waiting to be certified.

Representatives from SEIU commented that once this happens, 5,300 of the 7,000 janitors in Houston will have union representation.