An experimental study on the effect of filter types, relative humidity and using two stage filters on the weight efficiency and pressure drop across the filter was carried out, to complete the study a test rig is designed and built, the rig consist of three sections air duct, of 30 cm ×30 cm cross sectional area, with overall length of 220 cm. Six types of air filters are used in a single stage filters; namely spongy, polyester, synthetic one and two layer aluminum filters. A molten Aluminum powder dust (Type Aluxite No. 25, 98% less than 35 microns and 2% less than 10 microns) is used. In two stage filters study the bag filter is used as a secondary filter while the primary can be any type of the five filters mentioned above. The study shows that the spongy filters gives a maximum efficiency when is used as a single stage filter as compared with the other filters type. Increasing of working environment relative humidity improves the weight efficiency for both single and two stage filters. Two stage filters can improved the filtration process, it is found that the combination of spongy filter and bag filters give a maximum of weight efficiency of about 92% when the relative humidity equals to 90% . Space distance between two stage filters affect the weight efficiency, it is found that the best distance between the spongy filter and bag filter is between 15 to 20 cm.