Zavim 5:9-10

Zavim 5:9

If someone ate neveila of a kosher bird and it’s still in his throat, he transmits impurity to two degrees and disqualifies trumah one degree more. If he stuck his head into the airspace of an oven, he is ritually clean and the oven remains clean. If he expelled or swallowed the neveila, he transmits impurity to one degree and disqualifies trumah one degree more. He remains clean so long as the neveila remains in his mouth, until he swallows it.

Zavim 5:10

If someone touches a dead vermin or semen, or if he was unclean with corpse impurity, or if he touched a metzora when he counts his seven days, purification waters in a volume insufficient to perform the sprinkling, a neveila or something ridden on by a zav – in all of these cases he transmits impurity to one degree and disqualifies trumah one degree more. The general rule is that whatever touches anything defined by the Torah as an av hatuma (a “father of impurity”) transmits impurity to one degree and disqualifies trumah one degree more except for a person (who transmits impurity to two degrees and disqualifies trumah one degree further). Once separated from the source of impurity, it transmits impurity to one degree and disqualifies trumah one degree more.