The present work represents an investigation for the pollutants emission when adding water to air in a continuous combustion chamber. Direct water injection into the chamber with water/fuel ratio up to 0.8, as well as, humidifying the inlet air with water prior to the chamber by changing humidity between 20 to 100%, has been examined at different equivalence ratio with gas oil fuel. The results with fuel droplet size of 80µm and Φ=0.8, show that when water directly injected, NOx and soot will decrease by 53% and 56.6% respectively. Nevertheless, CO and UHC are to increase by 108% and 84% respectively. On the other hand, when inlet air has humidified, the decrease in NOx and soot will be 17.15% and 17.94% respectively. But, CO and UHC show an increase of 13.5% and 8.47% respectively.