More information for this can be found in the Application Guide for the Projected-beam Smoke Detectors (DS240/DS241 and D296/D297) on the Bosch website www.us.boschsecurity.com
Location and Spacing The D296/D297 detectors allow a range of 30 ft to 350 ft (9 m to 106 m) and spacing up to 60 ft (18.3 m). Space the detectors no more than 60 ft (18.3 m) between projected beams and no more than half the spacing between a projected beam and a sidewall . You can determine other spacing based on ceiling height, airflow characteristics, and response requirements. In some cases, mount the transmitter on one end wall and mount the receiver on the opposite wall. You can also mount the transmitter and receiver up to one-quarter of the spacing distance from the end walls. See the following figure:
Q - A common question we get is can the beams be crossed?