To enhance the understanding of combustion-driven continuous wave (CW) DF chemical lasers, especially for knowing the situation of the generation of F atoms in combustion chamber and the excitation situation in the optical cavity, a series of experiments is carried out without diluent. The results show that, DF lasers will be in good condition without primary diluent, and lose a half of power and specific power without secondary diluent. The effect of diluents on lasers is discussed based on the results. DF lasers can run stably without diluent, which provides the evidence for the simplification of DF lasers.