The molecular speeds of gaseous molecules are analogous to those to rifle bullets , why do then odour of the gaseous molecular not detected so fast ?

Explanation

Though the molecules of a gas travel at high speeds but they do not travel in straight lines in one direction like bullets. As they travel, they collide with the molecules of the gases present in the air. As a result, they are deflected. Thus, they follow a zig-zag path, i.e., the net distance travelled in a particular direction is quite small in a given time. That is why the odour is not detected so fast.