The main purpose of this study is to investigate the effects of using oxygen enriched combustion (OEC) technology with high emission fuels (biodiesel and petro-diesel in different ratios) on an experimental four stroke internal combustion engine (ICE) Volkswagen passat and a water heating boiler. To do so, an experimental setup was prepared for each case. In both cases, the intake air was enriched by injecting pure oxygen to the combustion chamber and ensure appropriate mixing before reaching the flame, the highest oxygen enrichments levels are 24% in ICE and 27% in the boiler. A Bacharach module 300 combustion analyzer was used in order to monitor the required oxygen enriched intake air level and to measure the combustion process emissions. For internal combustion engine, it has been shown that using higher intake air oxygen concentrations with pure petro-diesel fuel or blended fuel (petro-diesel with biodiesel) increase the exhaust gas temperature obviously, the highest exhaust temperature improvement was 14%, it has been achieved when using 24% O2 concentration with pure petro-diesel. Also, it has been shown that biodiesel fuel intensify the combustion process and improve the exhaust gas temperature due to the additional oxygen quantities contained in it, results show that using B15 fuel with ambient intake air oxygen concentration (21% O2) improves the exhaust temperature 7.4%, this temperature improvement can be assumed as an indicator of the thermal efficiency improvement. However, similar stack gas temperature improvement has been achieved when implementing the same experiments on water heating boiler, 21.1% temperature improvement has been achieved when using 26% O2 intake air concentration with pure petro-diesel and optimum excess air conditions, this improvement is about 3.8% in terms of efficiency improvement. In addition, using OEC with either the internal combustion engine or the water heating boiler affects the exhaust emissions by increasing or decreasing its quantities. In ICE, NOx emissions increased when using oxygen enriched intake air with blended fuel, but it has been decreased when using either higher intake oxygen concentration or higher biodiesel fuel concentrations. NOx emissions decreased in the water heating boiler case when operating under theoretical excess air level with respect to optimum excess air level due to the reduction in the ballast N2 entering the process. Experimental results show that CO emissions decrease by using higher intake air oxygen concentrations with pure petro-diesel in both of the internal combustion engine and water heating boiler, it has been clearly noticed that when operating under theoretical excess air conditions in the boiler case, 77.2% CO emissions reduction have been achieved when using 26% O2 intake air concentration. In addition, CO exhaust emissions were reduced by using blended fuels (higher biodiesel concentrations) with ambient air oxygen concentration (21% O2) as a result of the additional oxygen quantities enter the process and improve its completeness. But it has been shown that CO exhaust emissions increase in the internal combustion engine case when using higher intake air oxygen concentration with higher biodiesel fuel concentration at the same time, it happened as a result of CO prompt formation, results show that when using 23% O2 intake air and B15 fuel, CO emissions increased 150.3% with respect to using 23% O2 intake air and B0 fuel, but when analyzing the same results with respect to using 21% O2 concentration with B15 fuel, CO emissions increased 104.5%. Similarly, SO2 emissions did not change when using OEC technology or biodiesel fuel in the ICE, but when operating under theoretical excess air conditions in the boiler section, SO2 emissions were very high and it has been reduced by using oxygen enriched intake air and/or biodiesel fuel.