John,
Welcome to the site. There could be a number of reasons why you smell odor. Depends on the odor and other factors. We did a post a couple of months ago on smells. It may depend on some of the following:
Do you use a one piece or two?
Do you take omega 3 pills or eat lots of asparagus?
What is the brand of pouch do you use?
What type of ostomy do you have?
Does the pouch have a gas filter?
One piece is completely watertight without a gas filter. I avoid using these as the filter works for shit and can get clogged easily. Better to burp the bag. Other opinions may vary.
If it smells like shit or urine, it could be the seal or filter if that's what you're using, or a leak. Taking omega 3 pills will permeate the pouch and you will smell a fishy metallic smell.
Some brands have better construction than others. Nuff said.
Since I don't know what type of ostomy you have, I can't tell what smell you're dealing with.
Filters suck. Period.
Hope this points you in the right direction.
Bain