Calculation formula for the minimum safety distance for AOPD with parallel approach (danger zone guarding):

The following calculation formula applies for applications of optoelectronic protective devices with approach direction of body parts parallel or in an angle up to 30° to the protective field level. The formula is derived from the ANSI formula and based on the principles of EN 999. With protective devices arranged in this way the safety distance from the point of operation is measured from the furthest away protective field boundary, as the detection of the body part begins here (see page 41, fig. 4.2.1-5).

Ds = Hs x (Ts + Tc + Tr + Tbm) + DH

DH = 1200 mm – (0.4 x H)
DHAdditional distance for lower limbs. DH always at least ≥ 850 mm (arm length)
HHeight of protective field above reference plane (floor).
Permissible installation heights H of a protective device with resolution d [mm]:
15 x (d – 50) ≤ H < 1000 mm
Required resolution d of a protective device with installation height H:
d [mm] ≤ H / 15 + 50 mm


If H is greater than 300 mm (12 inches) there is danger of room to crawl under. This must be taken into account with the risk assessment.