tries to lift the bottom end of the curtain 1 when said curtain is in the lowered position the safety system thus acts both as a break in detector and as an obstacle detector in the example shown in fig3 and 4 the bottom end of the curtain 1 is provided with a rigid bar 3 naturally the safety strap 10 may also be fixed directly to the bottom of said curtain 1 and the invention is thus also applicable to a roll up curtain that has no rigid and or heavy element at its bottom fig5 and 6 show the use of the safety system of the invention on another type of goods handling door namely a stack up goods handling door in this type of door the curtain 1 is said to be flexible either because of its material or because it is made up of rigid panels that are hinged together about hinge bars 4 in this case the curtain 1 is not rolled up about a roller as described above but rather it is stacked up in known manner at the top of the apparatus said curtain is opened and closed by means of one or more actuating straps 10 39 which are therefore tensioned while the curtain is being displaced and which are rolled up at the top end about a roller 11 for raising and lowering the curtain 1 said actuating straps 10 39 are preferably fixed to a rigid and.