Abstract: A tension adjusting sash suspension arrangement for a vertically reciprocal sash for a fume hood having a cable connected to opposite sides of the sash, threaded over front corner pulleys, threaded around rear corner pulleys, threaded through a tension adjusting mechanism and directed downwardly to a common counter weight. The tension adjusting mechanism includes two laterally arranged pulleys mounted rotatably on a sliding bracket. The sliding bracket is slidable along a fixed bracket and fixable in selected position along a slot. The cable lengths are adjusted by loosening the sliding bracket with respect to the fixed bracket and allowing the counter weight to take up all tension in the cables, and then fixing the sliding bracket in position. The sash counter weight system can be precisely adjusted for proper vertical movement of the sash without binding caused by a skewed travel.