Although it has been widely recognized that fit testing is a critical requirement for ensuring the efficacy of tight fitting respirators, it may not always be complied with for various reasons, including availability, cost and time. Therefore, a less burdensome fit test method for respirators may help increase compliance. In this study, the particle size distributions generated by commercially available aerosol nebulizers (3M FT-10 and TSI Q-Fit) for qualitative fit test and pneumatic medical nebulizers were explored, respectively. Then, a combination of a filtering facepiece and a controlled leakage was used to calculate the fit factors according to the particle size distributions and defined aerosol penetration data. The result showed that inexpensive pneumatic medical nebulizers could be substitutions for the 3M FT-10 and the TSI Q-Fit aerosol generators.