The invention relates to a boom apparatus for an agricultural sprayer, comprising a first boom section of a boom provided with a plurality of sprayer elements for dispensing a product； a second boom section of the boom, the second boom section foldably connected to the first boom section in such a way that the second boom section is pivotable between an extended position in which the second boom section is outwardly extending from the first boom section for forming an extended boom and a folded position in which the second boom section is folded from the extended position in a folding direction for forming a folded boom. A pressure relief apparatus (33) is provided, comprising a pressure relief flow line (34) connecting the first and second cylinder sub-chambers (29, 30)； and a pressure relief valve (35) provided in the pressure relief flow line (34) in such a way that, in the operation mode, the pressure relief flow line (34) is in a normally blocked condition in which the pressure relief flow line (34) is blocked by the pressure relief valve (35). The pressure relief flow line (34) is in an open condition by the pressure relief valve (35) opening if, because of the second boom section (4) colliding with an obstruction and pivoting rearwardly from the extended position toward the folded position, a pressure in one of the first and second cylinder sub-chambers (29, 30) is exceeding a threshold pressure, thereby, allowing a hydraulic fluid flowing through the pressure relief fluid line (34) directly from the one to the other of the first and second cylinder sub-chambers (29, 30)； and the pressure relief flow line (34) is returning to the normally blocked condition by the pressure relief valve (35) closing if the pressure is falling below the threshold pressure. Further, an agricultural sprayer and a method of operating a boom apparatus of an agricultural sprayer are provided. (Fig. 3).
