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.