Baking fish and meat in the same oven:[1]

A. Simultaneously:[2]

It is forbidden to bake fish and meat in the same oven, simultaneously.[3]

Covered fish/meat: If the fish and meat are both hermetically covered in a way that vapor is not released during the baking, then everything remains permitted.[4] Furthermore, even if only one was covered and the only other was uncovered, seemingly both remain permitted.[5] However, initially, one should not cook the fish and meat in the same oven simultaneously even if both foods are hermetically covered.[6]

Bedieved: Although in previous times when medieval ovens were in use, fish and meat that were baked simultaneously within a large[7] oven would remain permitted[8], nevertheless, in today’s modern-day ovens, if both the fish and the meat were uncovered, then both the meat and fish are forbidden[9], unless either the fish or meat has 60x one versus the other in which case the food that has 60x against it is forbidden and the majority food is permitted.[10] Whatever the case, the oven does not need to be Kashered, although one should wait 24 hours before using it.[11]

B. Baking fish and meat in the same oven-One after the other:[12]

No residue:[13] It is permitted to bake fish in an oven in which one previously baked meat, and it is permitted to bake meat in an oven in which one previously baked fish, so long as the oven is clean of any meat/fish residue, or the food is hermetically covered. This applies even if the oven is Ben Yomo from its previous use.[14] [Some Poskim[15] rule that even those who are stringent to not cook fish in a meat pot, may be lenient regarding this matter to bake fish in a clean meat oven. Some, however are accustomed to be stringent to only bake fish in a Pareve oven.[16] This especially applies if it is difficult to ascertain whether the oven contains any meat residue, in which case it is best to always cook the fish in a Pareve oven, or to cover it.]

There is residue: If one baked uncovered fish in a meat oven that contains meat residue, then the fish is forbidden to be eaten unless it contains 60x the meat reside.[17] The same applies vice versa, that if one baked uncovered meat in an oven that contains fish residue, then the meat is forbidden to be eaten unless it contains 60x the fish reside

How to clean an oven of residue:[18] The only way a proper cleaning can be accomplished is through performing Libun [even Kal] inside of the oven. [This can be accomplished by turning the oven on to a hot temperature for about 15 minutes and having it burn out any leftover residue.[19]] It does not suffice to merely clean the oven with a sponge and water, without also turning it on and burning any leftover residue that is inside.[20]

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[1] See Sefer Shemiras Haguf Vihanefesh [Lerner] 1:16; Pesakim Uteshuvos 116:8

See regarding baking fish and meat simultaneously in same oven of previous times, regarding if we say Reicha Milsa Hi: Rama Y.D. 116:2 that one may not do so due to Reicha, although Bedieved it is permitted; Darkei Moshe 116:3; Toras Chatas 76:11; Issur Viheter 39:25 and 29; Rashal in Yam Shel Shlomo Chulin 7:15 [lenient even initially-no Sakana]; Shach 116:1 [lenient, although in name of Beir Sheva is stringent]; Derisha 116:5 [stringent]; Taz 116:2 [permitted even initially]; Peri Chadash 116:4 in name of Beir Sheva 35 that Reicha is forbidden even bedieved by fish and meat due to Sakana Chamira Meissura; Peri Toar 116:3 [stringent by fatty meat/fish]; Minchas Yaakov 86:26; Aruch Hashulchan 116:10 [permitted Bedieved]; Stringent by small oven: Minchas Yaakov 86:26; Lechem Hapanim 116:3; Beis Lechem Yehuda 116:4;  Chochmas Adam 68:1; See Ran Chulin 93b; Kneses Hagedoal 116:18; Darkei Teshuvah 116:22; Kitzur SHU”A 33:1 [permitted by large ovens of today, but not by small ovens of previous times unless one is covered]; Kaf Hachaim 116:23-24; Halacha Berurah O.C. 173:9 

See regarding the issue of vapor: Michaber and Rama Y.D. 92:8; 108:1 regarding baking under the same roofing which causes Zeiah, which is Mamashus to travel

See regarding the status of today’s ovens: Igros Moshe Y.D. 1:40 in length for the Zeiah concerns in our ovens and that they have the same status as a pan placed over two uncovered foods, brought in Rama 108:1; Maharsham 3:208; Minchas Yitzchak 5:20; Chelkas Yaakov 2:136; Kinyan Torah 1:24; Badei Hashulchan 92:166; Darkei Halacha p. 242

[2] Rama Y.D. 116:2; All Poskim ibid who prohibit initial cooking due to Reicha even in ovens of previous times; All Poskim ibid regarding Zeiah

[3] The reason: It is forbidden to eat meat and fish together due to danger, and this danger applies whenever the flesh or gravy of meat and fish mix together. Now, whenever one cooks thing simultaneously in an oven there is a question of whether the tastes of the food mixed with each other due to the smell and vapor that they expel into the oven. In the ovens of previous times, the issue of vapor was very scarce being that the ovens were very large and contained large chimney holes which allowed the vapor to escape before falling back onto the foods. Accordingly, the only issue that the Poskim dealt with in cases of foods that were baked simultaneously in the same oven, is the issue of smell, of which we rule Bedieved that “Reicha Lav Milsa Hi,” that smell of a food is not an issue, and hence even if one baked fish and meat in the same oven while both were uncovered, many Poskim rule that they remained permitted [although some are stringent]. However, this ruling was only truly by the ovens of previous times, however, by the ovens of today the Poskim conclude that there is an additional issue of vapor, and hence the law changes. Now, since vapor commonly carries the actual substance of the product, when one bakes the uncovered meat and fish in the same oven, the vapor of the meat enters into the fish and the vapor the fish enters into the meat, hence rending them both forbidden. For this reason, it is imperative that one never bake fish and meat at the same time in the same oven, and at the very least, if one needs to, one is to make sure that they are both hermetically covered.

[4] The reason In the event that both of the foods are covered, then there is no worry of vapor and smell, as the vapor and smell of the foods do not escape the cover and hence there is no worry of intermingling of the two gravies.

[5] Chochmas Adam 68:1 and Kaf Hachaim 116:23 regarding Reicha; See Admur 447:10 and Michaber 108:1 that it suffices for even one of the foods to be covered, however, that is regarding Reicha. However, regarding Zeiah, so long as the vapor of one of the foods hits the other food, it is forbidden, and thus both foods must be covered; Vetzaruch Iyun from Kaf Hachaim 108:32 who explains that the Zeiah case which prohibits is if both the Heter and Issur are uncovered;

The reason: In the event that only one is covered, then while there is no worry that the covered product will release vapor, the uncovered product will release vapor and it thus can prohibit the covered product as a result. However, in truth one can argue that since by mixtures of meat and fish the Poskim rule that only if the two substances actually mix do they become forbidden, and not through mere absorbance of taste, therefore by fish and meat even the covered food remains permitted as it only absorbs the taste of the vapor of the other food through its cover and not the actual vapor. [See regarding that by fish and meat there is no prohibition of taste: Implication of Michaber 95:1 and Chulin 111a “One who roasts fish in a meat pot may eat it”; Taz 95:3 “One can learn from here that there is no danger in eating fish that contains the taste of meat through being cooked in a Ben Yomo pot of meat”; Issur Viheter 39:26 “All secretion of taste of meat that is absorbed in a vessel into fish is not Bedieved forbidden due to danger”; Rashal Kol Habasar 9; Kneses Hagedola 116:18; Minchas Yaakov 57:1 concludes “The custom is to be lenient [even initially-Kaf Hachaim 116:20] if the pot is clean”; Peri Megadim 95 M.Z. 3 defends the ruling of the Taz ibid; Lechem Hapanim 116:3; Beis Lechem Yehuda 116:4; Chochmas Adam 68:1; Eidos Biyihosef 2:46; Divrei Hilel 2:32; Daltei Teshuvah 95:5; Ikareiy Hadat Y.D. 14:10; Zechor Leavraham 3:186; Darkei Teshuvah 116:27; Kaf Hachaim 116:20; Sheivet Halevi 6:111 writes it is the custom of the world to be lenient.]

[6] Rama 92:8 regarding meat and dairy, and the same should apply to fish and meat; Pesakim Uteshuvos ibid footnpte 86

[7] The law by a small medieval oven: Some Poskim rule that by a small oven, Reicha is forbidden even Bedieved by mixtures of Sakana of fish and meat. [Minchas Yaakov on Toras Chatas 86:26; Peri Chadash 116:4; Peri Toar 116:3 regarding if either the fish or meat is fatty, if, however both are lean then is permitted; Lechem Hapanim 116:3; Beis Lechem Yehuda 116:4; Chochmas Adam 68:1; Kaf Hachaim 116:23-24 regarding if either the fish or meat is fatty; See Ran Chulin 93b; Kneses Hagedoal 116:18; Darkei Teshuvah 116:22; Kaf Hachaim 116:23-24; Halacha Berurah O.C. 173:9] Vetzaruch Iyun. [See Divrei Malkiel 2:53; Mishmeres Shalom 116; Imreiy Yaakov 10 Likkutim 14] This, however, only applies if either the fish or meat is fatty, if, however both are lean then is permitted. [Peri Toar ibid; Zivcheiy Tzedek 116:13; Kaf Hachaim 116:24]

[8] Rama Y.D. 116:2 that one may not do so due to Reicha, although Bedieved it is permitted; Darkei Moshe 116:3; Toras Chatas 76:11; Issur Viheter 39:25 and 29; Rashal in Yam Shel Shlomo Chulin 7:15 [lenient]; Shach 116:1 [lenient]; Taz 116:2; Minchas Yaakov 86:26; Aruch Hashulchan 116:10

If the gravy of the meat touched the fish or vice versa: Then the fish, or vice versa, is forbidden even in medieval day ovens. [Shach 116:1; Issur Viheter 39:28; Toras Chatas 77:11; Kneses Hagedola 116:18; Beis Lechem Yehuda 116:4; Kaf Hachaim 116:22] If, however, the gravy became absorbed in the floor of the oven which then had fish cooked on it, then it remains valid. [P”M 105 S.D. 5; Kaf Hachaim 116:16]

Other opinions: Some Poskim rule that Reicha is forbidden even Bedieved by fish and meat due to Sakana Chamira Meissura [Shach 116:1 and Peri Chadash 116:4 in name of Beir Sheva 35; Peri Toar 116:3; Chochmas Adam 68:1]

[9] See all Poskim in first footnote for the law regarding vapor and modern-day ovens; This does not fall under the Heter of 116:2 regarding baking fish and meat in an oven, in which case we rule that Bedieved it is valid, as there it is only dealing with a problem of Reicha.

The reason: It is forbidden to eat meat and fish together due to danger, and this danger applies whenever the flesh or gravy of meat and fish mix together. Now, whenever one cooks thing simultaneously in an oven there is a question of whether the tastes of the food mixed with each other due to the smell and vapor that they expel into the oven. In the ovens of previous times, the issue of vapor was very scarce being that the ovens were very large and contained large chimney holes which allowed the vapor to escape before falling back onto the foods. Accordingly, the only issue that the Poskim dealt with in cases of foods that were baked simultaneously in the same oven, is the issue of smell, of which we rule Bedieved that “Reicha Lav Milsa Hi,” that smell of a food is not an issue, and hence even if one baked fish and meat in the same oven while both were uncovered, many Poskim rule that they remained permitted [although some are stringent]. However, this ruling was only truly by the ovens of previous times, however, by the ovens of today the Poskim conclude that there is an additional issue of vapor, and hence the law changes. Now, since vapor commonly carries the actual substance of the product, when one bakes the uncovered meat and fish in the same oven, the vapor of the meat enters into the fish and the vapor the fish enters into the meat, hence rending them both forbidden. For this reason, it is imperative that one never bake fish and meat at the same time in the same oven, and at the very least, if one needs to, one is to make sure that they are both hermetically covered.

The law by meat and fish without gravy: See Pesakim Uteshuvos ibid who writes that dry fish and meat do not release vapor, however, in truth many Poskim rule that all food products release vapor, whether liquid or solid, aside for the fact that all fish and meat have natural gravy released when cooked. [Tur 451:15 regarding Charara “And it releases vapor”; Bach 451:13; M”A 451:30; Yad Yehuda 92 Aruch 53; Masas Binyamin 42:58; Chacham Tzvi 20; P”M 451 A.A. 30; Rivash 295; Tzemach Tzedek O.C. 43; Shoel Umeishiv Chamisha 4; Beis Shlomo Y.D. 1:162 and 164; Maharsham; Daas Sofer; Levushei Mordechai; Poskim in Darkei Teshuvah 92:164; Rav Elyashiv in Beis Yitzchak; See Peri Haretz Y.D. 2:14]

[10] Peri Chadash 116:4; Lechem Hapanim 116:3; Beis Lechem Yehuda 116:4; Zivcheiy Tzedek 116:14; Kaf Hachaim 116:25

[11] See Darkei Teshuvah 116:28; Kaf Hachaim 116:13; Imreiy Yaakov 10:41; Sefer Shemiras Haguf Vihanefesh [Lerner] 1:15

[12] See Igros Moshe 1:40; Pischeiy Halacha p. 27; 157; Kinyan Torah 1:24; Minchas Yitzchak 5:20; Hakashrus 1:39-40

Background: As explained in A, modern ovens today contain a Zeiah prohibition. Accordingly, the roof and walls of an oven are saturated with taste of the foods cooked in it and receive a meat/fish status similar to that of a meat/dairy pot. Thus, if one cooks fish in a meat oven or vice versa, it is viewed similar to having cooked fish in a meat pot or vice versa. This is in addition to the possibility of the oven containing meat or dairy residue which can release vapor and enter the food.

[13] Pesakim Uteshuvos ibid and 92:22 footnote 274; Koveitz Mibeis Levi Inyanei Y.D. p. 41

[14] The reason: As the danger of eating fish with meat only applies if it contains substance of the meat, and does not apply towards the indirect taste transferred through a pot. [Taz 95:3 “One can learn from here that there is no danger in eating fish that contains the taste of meat through being cooked in a Ben Yomo pot of meat”; Issur Viheter 39:26 “All secretion of taste of meat that is absorbed in a vessel into fish is not Bedieved forbidden due to danger”; Rashal Kol Habasar 9; Kneses Hagedola 116:18; Minchas Yaakov 57:1 concludes “The custom is to be lenient [even initially-Kaf Hachaim 116:20] if the pot is clean”; Peri Megadim 95 M.Z. 3 defends the ruling of the Taz ibid; Lechem Hapanim 116:3; Beis Lechem Yehuda 116:4; Chochmas Adam 68:1; Eidos Biyihosef 2:46; Divrei Hilel 2:32; Daltei Teshuvah 95:5; Ikareiy Hadat Y.D. 14:10; Halef Lecha Shlomo O.C. 312-313; Chinuch Beis Yehuda Y.D. 61; Zechor Leavraham 3:186; Darkei Teshuvah 116:27; Kaf Hachaim 116:14, 16, 20; Sheivet Halevi 6:111 writes it is the custom of the world to be lenient.]

[15] Pesakim Uteshuvos ibid and 92:22 footnote 274; Hilchos Basar Bechalav 12:50 in name of Rav Klein

[16] Rav Landau

[17] The reason: As the residue releases vapor and Reiach which becomes absorbed within the fish and makes it forbidden.

[18] Michaber 97:2

[19] Kinyan Torah 1:24; Minchas Yitzchak 5:20; Hakashrus 1:40

[20] Taz 97:4; Peri Chadash 97:4; Chavas Daas 97:9; Aruch Hashulchan 97:12; Kaf Hachaim 97:34]

The reason: As the fat does not clean off well and requires the oven to be lit in order to burn the fat. [Poskim ibid]