Ozone (O3) is the highly unstable triatomic oxygen molecule that is formed by addi o n of an oxygen atom to molecular diatomic oxygen (O2). With regard to instability of Ozone, it is a powerful antimicrobial substance due to its potential oxidizing capacity. There are many suggested applications of ozone in the food industry such as surface hygiene, sanitation of food plant equipment, reuse of waste water and decontamination of poultry carcasses. Processing and handling conditions of poultry carcasses after slaughter result in high levels of micro-organisms, including some human pathogens. Each micro-organism has an inherent sensitivity to ozone. Bacteria are more sensitive than yeasts and fungi. Gram-positive bacteria are more sensitive to ozone than Gramnegative bacteria and spores are more resistant than vegetative cells. Chlorinated water is used in some countries to control microbial grow-out, cross-contamination or contamination? Chlorine inhibits glucose oxidization in the bacteria and shows bactericidal effect. It also decreases the activations of some enzymes that carry sulfide group. However, excess usage of chlorine forms toxic and carcinogenic compounds called tri-halo methane by reacting with the meat. However, the EU does not allow the addition of chlorine to process water during poultry processing. The chlorine levels do not normally exceed 50ppm, which results in a reduc o n in microbial load of just 1 log cycles. In this study, two poultry abattoir with ozone and chlorine treatment were compared, based on total aerobic bacterial count. Maximum level of using ozone was 0.5 ppm whereas the maximum level of chlorine was up to 40 ppm. A e r the chilling stage, whole chicken carcasses were rinsed with 250 ml of normal saline 0.9%. Serial ten-fold Dilutions were made. Total aerobic bacterial Count was done with surface plate count method using plate count agar medium. Mean of Total aerobic bacterial counts of ozonated and chlorinated abattoir were 7.6 × 104 and 2.5 × 105 cfu ml-1,respec v ely. Using sta s c al analysis, there was significant difference (P< 0.05) between these two decontamination systems. Since the mechanism of the ozone action, which destroys the microorganism through cell lysis, it cannot lead to micro-organism resistance; more detailed studies are needed to investigate the efficacy of ozone on poultry carcass decontamination. Notably, when ozone is applied to food, it leaves no residues since it decomposes quickly

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