One who passed gas with a smell, may not recite any Davar Shebikedushah, including studying or thinking in Torah topics, as long as the odor is present. If one does want to recita a Davar Shebikedushah, one must distance oneself to where the smell ends. Others, however, may not recite a Davar Shebikedusha, but may study Torah. This applies to any time where the tangible source of the odor is not present.