Using an Oven for Meat and Dairy, or a non-Kosher Oven

In the Kollel recently, we learned the Halachos relating to the Kashrus issues of Zei’a, steam. One of the most practical applications of this issue is the propriety of using a single oven for meat and dairy.

The main potential problem would be the suspicion that vapors rose from the previous food cooked in the oven, carrying say Fleishig flavor, and deposited it on the roof of the oven. If this meaty taste would be likely to end up in a subsequent dairy food, a Kashrus issue would be present.

Additionally, if one is renting an apartment of visiting irreligious relatives, the issue would inevitably arise whether one may eat food cooked in the oven.  The oven was previously utilized to cook non-Kosher food, must one be concerned that theTreif flavor will contaminate his Kosher meal?

As a disclaimer, I certainly highly recommend that for various practical considerations one should avoid using the same oven for Milchigs and Fleishigs without processing it in between. Also, an oven that becomes Treif should be Kashered in an appropriate manner before using. The question is, under exceptional circumstances where there is no acceptable alternative, are there adequate Halachic grounds for temporary leniency?


There are numerous factors at hand, let’s analyze them one at a time:

1)      Is steam rising off of a food equivalent to the food itself? Not only is it forbidden to eat certain foods, but ingesting their flavor is forbidden as well. So, eating potatoes from a stew that contains non-Kosher meat is certainly forbidden. The Rishonim derive from a case mentioned regarding Taharos that the vapors emitted by a pot of liquid have the identical Halacha as the liquid itself. However, one rarely places a pot of soup inside the oven. The Pri Megadim quotes authorities that the above Halacha is limited to liquids and not relevant a solid food.

2)      Is there any steam? Even more basic of a consideration, Reb Moshe Feinstein zatzal challenges the assumption that solid foods emit significant steam. He suggests that when baking or roasting a generally dry food, it can be assumed that no vapors were emitted unless it was directly observed to the contrary.

3)      Does the steam reach the roof of the oven? An oven is an intrinsically hot and extremely dry environment. It is very logical to assume that any vapors that are expelled by the food being cooked will dissipate and dry up before reaching the ceiling of the oven. In fact, some Achronim observe that Zeia is exclusively mentioned regarding a pot on a stove; however, when the Gemara discusses potential problems inside an oven it limits the discussion to the much more lenient Reicha. They suggest that it can always be presumed that any steam that rises off of a roasted food burn up before causing any harm.

4)      Even if we suspect that forbidden steam emanated from the non-Kosher food and reached the upper expanses of the oven, are they edible? There is a general principle in Hilchos Kashrus that a forbidden food that becomes inedible to the average human is no longer Assur to consume inadvertently. Even if it is edible, if it does not contribute any enhancement to the flavor of the food it enters, it cannot render the formerly Kosher food problematic. Any accumulation of grease on the roof of an oven is unlikely to be appetizing, if edible at all. Especially after any prolonged exposure to the intense heat inside the oven, the singed and charred residue is unlikely to remain Kashrus concern to your new recipe.

5)      After all the above, we still need to explain how any delicious absorbed flavor is reaching the new, Kosher food being cooked. If the second dish is moist enough to fill the oven with a cloud of steam that circulates from the top back to the bottom, we have found a potential conduit for the Treif or meat/dairy to mingle. In lieu of this weather formation, any non-Kosher flavor on the ceiling of the oven is likely to remain there.


In conclusion, while I reiterate that I strongly suggest not using the same oven for uncovered Milchigs and Fleishig without running a cleaning cycle in between; when the need arises, it seems obvious to me that one may be lenient.

However, certain precautions should be taken. If one must use an oven for both milk and meat, the rack upon which the pan is placed should be cleaned well, and preferably a sheet of aluminum foil placed under the pan. Care should be taken that the pan and food avoids any contact with the possibly dirty surfaces of the oven. Ideally, the food should be covered, at least loosely.


All the above applies exclusively to a conventional oven. In a future article we will hopefully address the microwave.

13 thoughts on “Using an Oven for Meat and Dairy, or a non-Kosher Oven

  1. I would just like to point out that R’ Elyashiv ztzkllh”h held that it is impossible for ze’ah NOT to be emitted, even from a solid food in a double seal, as if that were the case, the sealed wrapper would burst.
    He therefore held that everything emitted ze’ah.

  2. I have to tell you that I was planning on writing about these halachos in my own weekly email! I haven’t had the chance to read what you wrote yet but it looks interesting.

  3. Thank you for this! It really is a lot of help. How does double wrapping help? and how can you keep an oven Parve while still cooking Meat? Can you burn out the oven inbetween?

    • You’re welcome.
      Placing foil under the pan prevent direct contact between the pan and any residue on the rack. While the foil may become Assur, it cannot transfer Issur to the pan of food.
      Covering, even when a single and not hermetically sealed layer, significantly reduces the likelihood of steam escaping. It also totally eliminates the possibility of any steam returning to the current food. I don’t see any need in a typical setting to double wrap (airline meals are different and must be double wrapped).
      Covering the meat, even lightly, should be enough to keep the oven Pareve. Whatever minimal quantity of steam escapes should not reach the walls and ceiling of the oven in a visible form. If the roast contains a lot of liquid, this may not be sufficient.
      Burning out an oven on a self-clean cycle is certainly effective. Merely running it on high is much less so, but in my opinion it is almost never really necessary anyways, so it certainly adds an added layer of Halachic protection.

  4. The Shulchan Aruch in YOD rules based on the ROSH’s psak that zeiah, per se, is not an actual issue unless the meat/milk is within a close proximity to it’s opposite to the extent that the meat/milk becomes “yad soledet” because of the [opposite]. If that is not the case, if it is further away than that, then even if we would – as the ROSH says was the minhag – dry the meat over pots of boiling milk (I assume that the meat didn’t drip into the pot) it’s MUTAR!
    Having said that it follows that (although the poskim don’t hold this!) steam rising to the roof of the oven doesn’t present a problem as far as the halachos of basar bechalav is concerned! Even more that that the rama paskins (YOD 98, i believe) that even if meat and milk are cooked in the same oven at the same time so long as one of them is covered – there is no problem of REIACH (smell, which would seem to be the exact same issue as ZEIAH as in both cases there is no actual contact with the meat/milk). This is true even in a small oven (of which the halacha is talking about there) and even if it’s not double wrapped.
    Hence it follows that ZEIAH is only an issue when the meat and milk are cooked in the same oven at the same time. Quite possibly only when one is on top of the other.
    I know that this is not the prevalent psak of modern poskim, but it DOES seem to be what the Shulcan Aruch holds.

    • First of all, the Rema in YD 92:8 only mentions the provision of the steam itself being Yad Soledes Bo at the point of contact, and does not quote the words of the Rosh more precisely as you did to require the steam to be hot enough to heat the upper pot.
      Secondly, the Terumas HaDeshen mentions a second option. It is only essential that the steam itself is so hot when the upper pot is cold. However, when the higher surface is itself hot, the steam need not be hot. This is quoted in the Beis Yosef, Toras Chatas, Pri Megadim and Rabbi Akiva Eiger on the page of the Shulchan Aruch, and the Poskim generally do not disagree. I don’t know why the Rema failed to mention it in the Shulchan Aruch.
      In any event, I don’t understand the relevance of your point. If there would be steam in an oven, the steam would certainly be Yad Soledes Bo.

      The Halachos of Reicha are brought in the Shulchan Aruch in YD 108. However, Reicha is intrinsically different then Zeia. While we Pasken that Reicha Lav Milsa, Zeia certainly IS Milsa as seen in Siman 92:8. Also, only Reicha is limited to simultaneous cooking, while Zeia is clearly even consecutive, as the Rema writes explicitly in YD 108:1.

    • Separate ovens were not a relevant option for most people until post WWII and are not discussed by Poskim prior to this point. However, I don’t know how many baked Milchig recipes they had in Europe anyways.
      Certainly, the issue of roasting Kosher and non-Kosher in the same oven is already mentioned in the Gemara and Shulchan Aruch, but only relative to Reicha and not Zei’a.

  5. Great stuff! So bedieved it’s ok to use a treif (clean) oven to heat up or cook non-soupy foods if they’re covered?

  6. Pingback: Microwave Ovens | Kollel Shaarei Horaah

  7. Although Rav Lichtenstein permits one to eat in a home where the opinion of the Aruch Hashulchan is followed, he recommends that one adopt a stricter standard. He suggests that one either wait twenty-four hours between cooking milk and meat in the same oven

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