Section 27(7)(iii) in The Rajasthan State Pollution Control Board Employees Service Rules and Regulations, 1993
(iii)Where, adequate number of the candidates belonging to the Scheduled Castes or the Schedules Tribes, as the case may be, are not available within the zone of consideration specified above, the zone of consideration may be extended to five times the number of vacancies and the candidates belonging to the Scheduled Castes or the Scheduled Tribes, as the case may be, (and not any other) coming within the extended zone of consideration shall be considered against the vacancies reserved for them.