321. Separating Kosher and Non-Kosher

46:19 If cheese or other foods are in the possession of a non-Jew, even if they are sealed or marked kosher, if we don't know who sealed them, they may not be eaten. 46:20 We must be careful that a Jew and a non-Jew do not cook in two pots next to each other, one with kosher meat and one with non-kosher meat if the pots are uncovered. Similarly, we should not leave cooking pots with non-Jewish household employees unless there is a Jew at home who will come and go periodically.