Bad Breath or BO???

I wondering how does anyone know whether the are suffering from bad breath or bo?

I've read post on here about room filling BO and about ppl saying there bo smelled like things that they've eaten. One person said their bo smelled like gum when they chewed it or 3x worse than alchol when they've drank it based on comment ppl had made. I even read on this forum of ppl saying they believe their smell is coming from their anus.

I know bo is a issue for those tmau or other similar issues. But my question is if they can't smell it and only relying on what others say how do know what is stinking and from where.