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Show \\'hich in turn reduces the form a tion rate of the first arom a tic ring [7 - 9]. Otherwise, the presence of 02 in incineration process also has a promoting effect on aromatics formation because of the accelerated chain branching leads to an incrase in the C/O ratio and to enhance fuel pyrolysis and thus increased precusors of PAHs formation such as C2H2, C2H3 , CZH4 and C4H3. The fact that fundamental mechanisms involved PAHs and soot formation in the in·cineration process are the oxidation , pyrolsis , Diels -Alder reation, nucleation, coagUlation, aggregation , and agglomeration [5 ,6,7]. Furthermore, the PAHs formed can grow, condense or adsorbe onto the emitted particulates which will diffuse to the atmosphere. These air pollutants are potential danger to human health because of their mutagenicity or carcinogenicity. Thus, the objectives of this reseach work are focused to characterize the prescusors of PAHs formation ie., C6H6, PAHs compounds and soots formation under various incineration temperatures and oxygen supplies. The mutagenicity of the emitted gas from P. S. incineration is also concerned and focused. MATERIALS AND METHODS The 0 .2 gram of polystyrene (P . S. ) was incinerated at various temperatures and oxygen supplies in two-stage incinerator. The inflow gas consisted of the oxygen and nitrogen . The inflow rate was controlled at 2.0 ~L/min and at various oxygen ratios by use of the flotation flow meter and needle valves. Two- stage incinerator consisted of two furnaces, t\\-'o quartz tubes, an electronic balancer, a computer and a data acquisition system which is used for auto sampling, signal transfer and autorecording the mass losses of the P. S. and temperature changes with time from the P. S. incineration process, as shown in Figure ] . The rate of temperature increa se in the stage-one incinerator was controlled. at 35°C/min , and the maXImum temperature was controlled at 500°C. The temperature in the stage-two incinerator \vas controlled at various temperatures (clean-up temperature ), from 900°C to 1200°C . The theoretic residence time wa s 3 |