Hi, I have a strictly kosher kitchen, but I have a roommate who is not very religious. In our kitchen, she keeps strict kosher. However during Pesach I will be away, but she will be in the apartment. If she uses our regular dishes during Pesach to cook food (chametz or even if she avoids actual chametz), will that ruin the dishes, making them not kosher for the rest of the year? In other words, is it like chametz that is not sold before Pesach and cannot be eaten after Pesach?

Shalom, Thank you for your question. You are correct that chametz not sold or destroyed before Pessach is forbidden after the festival. If so, are the vessels used to cook chametz during Pessach also forbidden? The law is that the vessels used to cook chametz during Pessach (which is of course forbidden to do) are permitted after the festival (See Shulchan Aruch 447,1, and the Mishna Brurah 4 ibid). However, it may be that there are other problems with your roommate using the kitchen for chametz during Pessach. If it is your kitchen (as it sounds from your question) then firstly you must clean it from all chametz before Pessach, or carry out a sale of it to a non-Jew. If you sell it, it is certainly forbidden for your roommate to use it – it belongs to the non-Jew! If you cleaned it out completely, you still need to put away the chametz dishes so that they will not be used during Pessach. There is also a problem of putting a stumbling block before your roommate and letting her break the laws of Pessach with your dishes. If however the kitchen and the utensils are not yours, but belong to your roommate, then there is little you can do against her wishes. None the less, I suggest trying to reach an agreement with her that she does not use the kitchen for the week of Pessach, and that you clean it properly from any chametz. Blessings.