A utensil that never touches food directly (such as the grate on a stovetop) does not require tevila.
A utensil which is always used with something covering it, such as a toaster rack that always has silver foil on it, still requires tevila, since the covering is insignificant, and is considered to be part of the utensil. However, if there is always a real utensil separating between the food and the dish or pan and the food is never directly on the utensil, such as the glass in a microwave that one never places food directly on, then the utensil would not require tevila. The exception to this rule is a pot cover, which will be discussed below.
Disposable Bottles and Cans
Glass drink bottles, such as Snapple bottles, are subject to much debate. On the one hand, people only use them once. Most people view them as disposable. Once one finishes the drink, the bottle is disposed of. On the other hand, the bottle itself is very much a real utensil. These bottles are reusable, and these drink bottles get thrown away merely because we are living in a more affluent time.
The poskim give various reasons and solutions how to permit drinking from these bottles, and why they do not require tevila first. One opinion is that the bottle was not considered a utensil until a Jew opened it, and the Jew is the one that gave the bottle the status of a useable utensil. Therefore, the bottle does not require tevila.
Another solution is that one should have in mind not to acquire the bottle when buying the drink. As long as the bottle belongs to a non-Jew it does not need tevila.
Electric appliances that have metal or glass parts (including toasters, sandwich makers, urns, electric grills, etc.) require tevila. If the metal parts are removable, one may take those out and only do tevila on those parts. If the appliance is a single unit, the entire machine requires tevila. The plug and cord, if removable, do not require tevila. If they are not removable, only the part close to the body of the appliance needs to be submerged in the mikvah. The remainder of the length of the cord does not need to be immersed.
Most simple electrical appliances can be immersed quickly and dried for several days and will not break. In a case when it is impossible to immerse the appliance without breaking it, one should consult with a rabbi.
Ovens and Racks
Ovens do not require tevila, since the oven itself does not touch the food, and it is too large to be considered a cover. One should do tevila on the racks, without a bracha, since the racks have food baked directly on them at times. One who never bakes food directly on the racks, but uses a paper or aluminum foil to cover the racks should still do tevila without a bracha, since the disposable covering is insignificant, as explained above.
Peelers require tevila, since they come in direct contact with food. Further, peelers are often used for foods that are eaten raw, such as cucumbers and apples. Therefore, when doing tevila on a peeler, one should make a bracha. In a household where the peelers are only used for foods that are not eaten raw one should not make a bracha on the tevila.
Pot covers require tevila even though they do not touch the food directly. The Pri Chadash and the Aruch Hashulchan explain that since steam rises from the food and touches the pot cover, the cover is considered like it is the pot itself.
The Chelkat Binyamin adds that the cover traps the heat in the pot and aids in the cooking. From here it would seem that a cover that is only used for covering a container of cold food would not require tevila. However, it would be preferable to do tevila without a bracha, especially if the cover keeps the food better in some way, for example a cover on a bottle of soda that prevents the gas from escaping.
An air fryer is an appliance that allows one to mimic deep fried foods without all the oil. The food is placed in a metal basket and slid into a box. Inside the box, blowers shoot very hot air at the food, and as the hot air rushes around the food it mimics the environment of a normal deep fryer.
In order for the air fryer to work, there needs to be an environment which contains the hot air, and allows it to circulate and hold its temperature. The metal basket needs tevila since food goes directly in it. However, the outside of the air fryer is a bit more complicated. One can say that since the steam from the food in the basket touches the box, it is like a pot cover which requires tevila. On the other hand, perhaps the box around the basket does not aid in the cooking process, since the food gets cooked as a result of the direct contact with the air, and the external box does not require tevila. One should consult with a rabbi prior to using an air fryer, to determine the best halachic solution.
There is a dispute among the poskim whether one who is giving a dish as a present should do tevila before giving it to the recipient. However, a present is not the same as merchandise. One who purchases merchandise has no thought of using utensils when he buys them, he has no thought of its use for food. It is merely a piece of merchandise to buy and sell. However, one who buys a dish for a present does buy the dish to be used for food, he just does not intend to be the one to use it.
One should consult with a rabbi before giving mishloach manot that has a dish in it, because if the dish requires tevila, one may not place food on it without doing tevila first.
Containers made of glass or metal require tevila. However, since these are not usually used to eat with, rather they just store food for a later time, one does not recite a bracha when performing the tevila.
Urns and Percolators
Utensils for Raw Food
The Shulchan Aruch writes that some rule that a knife used for shechita does not require tevila, however, the Rama rules that one should do tevila without a bracha. The Taz and Shach explain that a knife for shechita is only used for food which is raw and still needs to be cooked, and therefore one cannot do tevila with a bracha.
There is, however, a distinct difference between how the Taz understands this halacha and how the Shach understands this halacha. The Taz learns that any utensil which touches food that is not at the final stages of preparation, still requires tevila without a bracha. However, the Shach understands that only a utensil which also has an alternate use for food that is already fully prepared requires tevila. An example of this is a knife for shechita, which can also be used to cut prepared food.
Some practical differences between the Taz and Shach would be a dough hook, rolling pin, meat grinder, meat tenderizer, and a sifter. All of these are utensils that have no use other than for a food which is still raw. According to the Taz one must do tevila without a bracha, but according to the Shach there is no need for tevila on such utensils.
Many poskim disagree with the Taz and rule that only a utensil that can be used for food which is ready to eat would be included.
The Pri Chadash adds that a knife for shechita makes a huge change in an animal. Without shechita, there is no way to eat an animal, and so it is a utensil of significance and requires tevila. Therefore, a knife for shechita which can also be used as a regular knife requires tevila. However, a utensil like a meat tenderizer, which has no use other than for raw meat, does not need tevila.
Utensils for Sale
A store owner is not responsible to do tevila on utensils that he intends to sell. If he performs tevila, there is a dispute among the poskim whether the utensil he did tevila for requires a new tevila when someone buys them. Since only a utensil which is used for food requires tevila, and the store owner has no intention of ever using the utensil for food, it may not require tevila. Further, if the store owner does tevila, the tevila may be useless, since the utensil only becomes obligated in tevilat keilim once a Jew purchases it for use with food.
The common custom is that one who buys a utensil which the store already did tevila to, should do a second tevila without a bracha.
There are two varieties of water coolers. Some water coolers are completely plastic, except for the metal pipe which runs through the reservoir tank to cool the water. Other water coolers have a metal reservoir for holding the cold water. The former may not require tevila, while the latter would require tevila.
There is another distinction in regard to water coolers. Some are connected to the water supply of the house, and are therefore considered to be connected to the ground, and therefore they are not considered utensils at all according to some poskim. Others have a bottle which is filled with water that is placed atop the machine. This type would require tevila if it has a metal reservoir.
 שו”ע שם סעי’ ד
 חוט שני טבילת כלים עמ’ כד, חלקת בנימין סי’ קכ ס”ק לד
 אג”מ יו”ד ח”ב סי’ מ
 שרידי אש יו”ד סי’ ב
 אג”מ יו”ד ח”א סי’ נז. ועי’ באג”מ יו”ד ח”ג סי’ כד בענין טוסטר שאין צריך טבילה דרק מייבש את הפת, והפת לא היה חסר כלום לפני ששם אותו בתוך הטוסטר.
 מנחת שלמה ח”ב סי’ סו אות ב, רבבות אפרים ח”ו סי’ ריא
 רבבות אפרים שם אות ג, הל’ טבילת כלים אות מב בשם הגריש”א
 הל’ טבילת כלים שם
 רמ”א שם סעי’ ה
 שם ס”ק טו
 שם ס”ק לב
 ערה”ש שם סעי’ לב, חוט שני טבילת כלים עמ’ מא, משמרת הבית פ”ג סעי’ יג
 אהלי ישרון ח”א פרק ג הע’ סח בשם בעל האג”מ
 משמרת הבית פ”ג סעי’ יג
 קיצור שו”ע סי’ לז סעי’ ח, חלקת בנימין סי’ קכ ס”ק ד
 בצל החכמה ח”ה סי’ ה
 חוט שני טבילת כלים עמ’ מד
 שו”ע ורמ”א שם סעי’ ה
 שם ס”ק ז
 שם ס”ק י
 ש”ך שם ס”ק יא, חכמ”א כלל עג אות ט, קשו”ע סי’ לז סעי’ ח
 שם ס”ק יד
 ט”ז יו”ד סי’ קכ ס”ק י
 שו”ת מנח”י ח”ז סי’ מג אות ב, שו”ת תשובות והנהגות ח”א סי’ תנב
 עי’ שיעורי הלכה להגר”ש פעלדער פי”א אות ה