Thanks for your question.
I assume you meant foul smell.
This usually caused by the bacterial overgrowth in the vagina also known as bacterial vaginosis.
This is due to the change in vaginal pH resulting in growth of 'bad' gas producing bacteria.
Medications like metronidazole vaginal cream daily for 7 days is good to treat this condition.
You should also consider taking probiotics ( lactobacilli) daily which also helps eliminating bad bacteria & 'gas'.
Thanks for the clarification.
Usually this is not normal--air coming out of the vagina.
This can raise the suspicion of a fistula between the vagina and the colon.
Please see a gynecologist to rule out this possibility which will need a surgical repair, if the medication mentioned above does not improve your condition.