Types And Description Backward inclined, backward curved bladesBackward inclined, backward curved blade is a highly efficient impeller design. Its employed to handle air and also used for gas medium containing lighter amounts of dust particles and at high temperatures. Reinforcements and surface hardening are done for extra strength, if required.Backward inclined, flat bladesAn efficient and strong shape, this design is a cost-effective alternative to the backward curved design but with flat blades instead of curved and radial tipped. This results in a slightly lower efficiency, compensated by handling moderate dust particles.