The reclamation of energy from the by-product of palm fresh fruit bunch (PFFB) after processing into palm oil can be seen as an alternative to fossil fuel process to save the cost. The running of boiler with PEFB is generally generated ashes dust which usually contains a small particles size. This may effect on health of workers working in the risky area by inhalation route. Wet dust control systems are an alternative effective method to capture airborne dust particles. However, the system configuration and the effective of the system vary depending on the goal and the design. This study is aims to design the appropriated water spray system to effectively control dust ashes of PEFB from boilers combustion. This study was designed the water spray system by using 12 spray nozzles which size of 0.5 inch installing zigzag on the left and right side of the dust collecting room. The nozzles head gap of 0.6 meters were setting at 2.65 meters high from the floor. The results of this study showed a significant reduction of both total dust and respirable dust concentration after open the designed water spray system. However, the respirable dust concentration measured at the back of dust collecting room was still a bit higher standard. The further study should conduct to test the effective of spray control by improvement the angle and direction of water spray. Changing the material of wall room from the corrugate iron sheet to the cement wall at the back of the room may co-help reduce the distribution of the dust at this point.