Size distribution of particles and their associated polycyclic aromatic hydrocarbons(PAHs) from indoor burning source is one of the most important factors for the risk assessment of human breathing exposed to indoor burning smoke.In this study,smokes of incense,mosquito coil incense,moxa and cigarette burning were simulated in a chamber,respectively.The smoke particles were collected with a MOUDI sampler and used for further PAHs analysis.In addition,an airborne particle counter was used to monitor the indoor particle number concentrations of moxa and cigarette smokes.The emission factors for particles varied in the range of 3.68-22.46 mg/g,and the size distribution peaked at 0.25-0.44 μm.As for the US EPA 16 priority PAHs,the emission factors ranged from 10.52 μg/g to 91.30 μg/g.The size distribution of PAHs from moxa smoke peaked at 0.44-1.0 μm,which was slight higher than those from other burning sources.The toxic equivalency(BaPTEQ) for benzo［a］pyrene(BaP) in particles less than 1 μm accounted for 85%-98%.The source characteristics ratios showed that moxibustion,cigarette smoke and incense burning could be categorized into biomass burning.The indoor particle number concentrations increased rapidly after the cigarette and moxa were lighted,then reached the maximum when they were burned out,and finally decreased exponentially in 4 h.Furthermore,the number concentrations of particles less than 0.3 μm decayed the fastest.