He worked at the department of health for twenty years.
Tips
usage
厅 (tīng) denotes a provincial-level bureau directly under a provincial government; the national counterpart is 部 (bù, ministry) — 卫生部, and the municipal one is 局 (jú) — 卫生局. So 卫生部 > 卫生厅 > 卫生局 in the admin hierarchy.