Mishnah Oholot 5:7-6:1 · Expert voice, Standard

Sugya Map

The sugya of Mishnah Oholot 5:7 through Mishnah Oholot 6:1 navigates the boundary between mobile utensils (keilim) and architectural spaces (ohalim), formalizing how a vessel can transcend its individual identity to serve as a functional roof or barrier against corpse-impurity (tumat met).

                                  Vessel Screening Capacity
                                              │
                    ┌─────────────────────────┴─────────────────────────┐
                    ▼                                                   ▼
       Independent Status (Keli Ba'almah)             Integrated with Architecture
         • "Ein keilim na'asin ohalim letaher"          • "Metzilin im dofnot ohalim"
         • Incapable of autonomous screening             • Annexes status of existing partition
         • Transmits impurity via ohel                   • Screens contents beneath or within
                    │                                                   │
     ┌──────────────┴──────────────┐                     ┌──────────────┴──────────────┐
     ▼                             ▼                     ▼                             ▼
Underneath Tum'ah           Above Tum'ah            Interior Apertures             Exterior Projections
Keilim atop chest           Keilim below chest      Cistern/hatch covers           Kefishah on pegs; Pot on beam
become tamei               become tamei            Screen if rimmed (1 tefach)     Debate: R. Akiva vs. Chachamim

• Core Issue: Can a vessel—which biblical law generally excludes from acting as an autonomous screening tent (ein adam ve-khelim na'asin ohalim letaher)—nevertheless protect (lehatzil) against overhead defilement when functionally tethered to existing structures (metzilin im dofnot ohalim)?
• Nafka Minot:
  1. Screening via External Projection: Whether a vessel affixed to the external facade of a residence requires literal physical contact with the wall, or if spatial adjacency within three handbreadths (lavud) or one handbreadth (tefach) suffices.
  2. Status of the Base: If a non-receptive vessel (e.g., stone, unbaked clay, dung) is elevated, does its non-susceptibility enable it to shield objects resting on top of it, or does its formal designation as a keli categorically disqualify it from acting as an autonomous protective partition?
  3. Structural Autonomy of Plugs (Metzilin Bifnei Atzman): When organic or portable matter (e.g., dried figs, straw baskets, doors) seals an aperture against tum'at ohel, must the barrier sustain itself under external collapse, or is static closure sufficient at the moment defilement arrives?
• Primary Sources: Numbers 19:14–15; Tosefta Oholot 6:3–5; Eruvin 44a; Shabbat 43b; Bava Batra 19b; Rambam, Mishneh Torah, Hilchot Tumat Met 21:4–5.

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Text Snapshot

כְּשֵׁם שֶׁהֵם מַצִּילִין מִבִּפְנִים עִם דָּפְנוֹת אֹהָלִים, כָּךְ מַצִּילִין מִבַּחוּץ. כֵּיצַד? כְּפִישָׁה שֶׁהִיא נְתוּנָה עַל הַיְתֵדוֹת מִבַּחוּץ, טֻמְאָה תַחְתֶּיהָ, כֵּלִים שֶׁבִּכְפִישָׁה טְהוֹרִין. אֲבָל אִם הָיָה כֹּתֶל חָצֵר אוֹ כֹּתֶל גִּנָּה, אֵינוֹ מַצִּיל. קוֹרָה שֶׁהָיְתָה נְתוּנָה מִכֹּתֶל לְכֹתֶל וּקְדֵרָה תְלוּיָה בָהּ, טֻמְאָה תַחְתֶּיהָ, רַבִּי עֲקִיבָא מְטַהֵר, וַחֲכָמִים מְטַמְּאִין. אֶחָד הָאָדָם וְאֶחָד הַכֵּלִים נַעֲשִׂין אֹהָלִים לְטַמֵּא, אֲבָל לֹא לְטַהֵר...

“Just as they protect inside together with the walls of tents, so they protect outside. How so? In the case of a large basket (kefishah) supported on pegs on the outside: if there was uncleanness beneath it, vessels in the basket remain clean. But if it was [next to] the wall of a courtyard or of a garden, it does not protect. [In the case of] a beam placed across from one wall to another, with a pot hanging from it, if there was uncleanness beneath it, Rabbi Akiva declares [the vessels inside it] clean, but the Sages declare them unclean. Both persons and vessels can form tents to convey uncleanness, but not to screen [against uncleanness] so that objects remain clean...”
— Mishnah Oholot 5:7

Textual & Grammatical Nuances

1. עִם דָּפְנוֹת אֹהָלִים (Im dofnot ohalim): The preposition im (“with” / “alongside”) implies co-dependence. The vessel does not generate an independent ohel; it annexes itself to an extant, halachically defined ohel. Where no pre-existing dofen ohel exists (e.g., kotel chatzer, a garden or courtyard perimeter constructed merely for privacy or demarcation), the vessel’s roof-forming capacity is void.
2. כְּפִישָׁה (Kefishah): A woven willow basket, typically daubed with clay or dung, which possesses a physical cavity. The mishnah specifies netunah al hayatedot (resting on pegs protruding from the wall) to establish that it is elevated at least one handbreadth (tefach) off the ground; without this gap, defilement cleaves directly through solid matter (tum'ah rotzetzet boka'at ve'olah).
3. קְדֵרָה תְלוּיָה בָהּ (Kederah teluyah bah): The syntactic ambiguity—whether the impurity is beneath the pot or beneath the beam—drives the fundamental machloket between Rambam and Maharam of Rothenburg.

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Readings

                         Architectural Integration Models
                                        │
           ┌────────────────────────────┴────────────────────────────┐
           ▼                                                         ▼
   Rambam's Direct Extension                               Maharam / Rash: Spatial
     (Structural Annexation)                               Continuity (Lavud Dynamic)
• Beam itself forms the ohel                           • Vessel extends the external wall
• Vessel is merely suspended within                    • Gap of <1 tefach bridges vessel to wall
• R. Akiva / Sages argue over vertical                 • Dispute centers on horizontal clearance
  distance between pot's rim and beam                    and projection of the house's profile

1. Rambam: Structural Annexation and the Mechanism of Direct Extension

In Hilchot Tumat Met 21:4–5, and his commentary on the mishnah, Rambam aligns the mishnah's mechanics with absolute spatial continuity.

       [ House Roof / Ohel ]
   ═════════════════════════════════  <- Beam (Width >= 1 tefach)
                 │ | (Hanger)
             ┌───────┐
             │  Pot  │  <- Rim flush with beam = Protected
             │(Keli) │  <- Rim separated by 1 tefach = Contaminated
             └───────┘  <- Rim separated by < 1 tefach = R. Akiva vs. Chachamim
                 ▲
                 │
              [Tum'ah] (Beneath Pot/Beam)

Rambam asserts that a vessel cannot shield its interior or upper surface merely by existing near an ohel. Rather:

• For the kefishah on exterior pegs: Its aperture or side must be directly flush with the exterior wall of the house (veyitdabbek b'shivui piv im tzidei habayit). Because the house's wall was built to define an interior living space (na'aseh le-ohel), any vessel mechanically integrated into that wall becomes an architectural extension of the ohel. Conversely, a courtyard wall (kotel chatzer) is open to the sky and designated purely for boundary demarcation; it possesses no legal status of ohel, and an attached vessel cannot draw protective vitality from it.
• For the kederah hanging from the beam: Rambam, as glossed by the Kessef Mishneh citing Rabbi Yitzchak Aboab and Radbaz, interprets the text inversely from its literal syntax. The phrase tum'ah tachteha refers not to the pot, but to the korah (the beam) traversing two walls. A beam of at least one handbreadth (potheach tefach) is an autonomous roof (ohel). When corpse-impurity lies beneath this beam, the beam draws the defilement horizontally along its entire length. If an earthenware pot hangs beneath it:
  • If the pot's rim touches the underside of the beam without a gap, the beam seals the pot, and the vessels inside remain pure.
  • If a vertical gap of one handbreadth (potheach tefach) separates the rim from the beam, the beam acts as an ohel over both the impurity and the open mouth of the pot, flooding the pot's interior with defilement.
  • If the gap is less than a handbreadth: Rabbi Akiva maintains that since no standard opening (petach) of a handbreadth exists, defilement cannot enter, whereas the Sages rule that because it is not physically attached, the overhead beam brings the impurity directly over the aperture. The Rambam rules in accordance with the Sages (chachamim).

2. Rash miShantz: Slanted Ohalim and the Spatial Continuum of the Exterior Wall

Rabbi Shimshon of Sens (Rash), citing the Tosefta (Oholot 6:3), rejects Rambam’s requirement of absolute physical sealing and reframes the phenomenon through the doctrine of shipu'ei ohalim (the slopes of tents) and the rules of lavud.

Rash notes that the Tosefta differentiates between an earthenware pot placed against an exterior wall and a kefishah:

• A basket mounted on pegs is judged as shipu'ei ohalim—an angled overhang continuous with the house's roofline. Just as impurity cannot enter the interior of a sealed house, it cannot enter the interior cavity of an exterior vessel that serves as a downward slope of that same roof.
• Regarding the kederah suspended from a beam spanning two walls: Rash analyzes the Tosefta's scenario where the beam projects slightly outward from the exterior wall. Here, the dispute between Rabbi Akiva and the Sages turns on lateral proximity:
  • If the pot is pulled away (meshucheh) from the beam or wall by an open handbreadth, all agree it cannot protect, because it is an isolated vessel (keli ba'almah), and ein keilim na'asin ohalim letaher.
  • If it is flush (dibuk), all agree it protects.
  • If the gap between the vessel's rim and the overhead beam/wall is less than a handbreadth (pachot mi-tefach), Rabbi Akiva applies the principle of lavud (or a diminished spatial aperture) to treat the pot as contiguous with the wall/roof structure. The Sages, however, restrict metzilin im dofnot ohalim to an unbroken structural whole; any physical breach—even sub-tefach—breaks the architectural union, reverting the pot to the status of an independent vessel, which cannot screen against defilement.

3. Maharam of Rothenburg: The Earthenware Backside Paradox (Gabo Shel Keli Cheres)

Maharam of Rothenburg (cited in Tosafot Yom Tov Mishnah Oholot 5:7:3) addresses a fundamental vulnerability in the structural paradigm: An earthenware vessel (keli cheres) does not contract impurity through its exterior surface (miggabo), yet it does not screen (chotzetz) against defilement if it is deemed a mere keli.

Maharam explains why the mishnah specifically discusses vessels inside the suspended pot (kelim she-be-tokhah):

• The mishnah does not state that the pot remains clean—the pot itself hangs below the beam, and if defilement passes under the beam, the pot's exterior would normally be irrelevant since ein keli cheres mitamei miggabo.
• The real issue is whether the pot functions as a roof to protect the utensils resting within its hollow interior.
• According to Maharam, the beam must project outside the house, hanging over an alleyway or garden. If the pot's rim is set directly beneath the beam's edge, Rabbi Akiva asserts that the pot's interior remains a separate domain shielded by its structural alignment with the beam. The Sages argue that because the vessel’s lips flare outward beyond the beam’s margins (sefatai ha-kederah meshukhin mi-sefat ha-korah ve-lachutz), its opening remains exposed to the open sky above the impurity. Thus, the vessel fails to form a single, sealed barrier in conjunction with the architectural elements of the house.

4. Chazon Ish: The Ontology of "Tent Formation" (Oholot, Siman 14)

The Chazon Ish reformulates the debate around the mechanics of metzilin im dofnot ohalim:

• Does the vessel become a genuine physical ceiling (gag) that merely relies on the wall for its structural foundation?
• Or does the wall cast a legal "shadow" or canopy (shem ohel), into which the vessel is subsumed?

The Chazon Ish demonstrates that if the vessel itself were considered an autonomous ceiling, it would violate the categorical imperative: Ein keilim na'asin ohalim letaher (vessels cannot serve as tents to protect). Therefore, the vessel does not act as an independent ohel. Instead, Halacha reinterprets the house's wall: the wall's status as a barrier extends laterally outward to envelop any vessel physically affixed to it.

Where the connection is interrupted by a gap of a handbreadth, the wall's architectural identity can no longer project into the vessel. Rabbi Akiva and the Sages argue over whether lavud can bridge this conceptual gap: Rabbi Akiva maintains that lavud extends the structural profile of the ohel to absorb the vessel, whereas the Sages rule that lavud only closes physical breaches in existing walls, but cannot construct a composite tent out of disparate entities (le-chaber keli le-ohel).

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Friction

                     The Core Conceptual Dilemmas
                                  │
         ┌────────────────────────┴────────────────────────┐
         ▼                                                 ▼
   Kushya 1: The Asymmetry                           Kushya 2: R. Akiva's
   Why does an independent keli                      Screening Mechanism
   act as an ohel to spread defilement,              How can an unsealed pot screen
   yet fail completely to screen against it?         without an airtight seal?
         │                                                 │
         ├─► Terutz A: Metzi'ut vs. Din                    ├─► Terutz A: Spatial Negation
         │   Intervention creates physical ceiling;        │   Sub-tefach gap negates
         │   Torah demands stationary structure.           │   the presence of an entrance.
         │                                                 │
         └─► Terutz B: Kal VaChomer Inversion              └─► Terutz B: Gabo Shel Keli Cheres
             Purity requires higher halachic status        Backside remains pure; defilement
             than impurity transmission.                   cannot enter a closed system.

Kushya 1: The Asymmetry of Vessel-Tents (Adam Ve-khelim Na'asin Ohalim)

The second half of Mishnah Oholot 5:7 states:

"Both persons and vessels can form tents to convey uncleanness (letamei), but not to screen (letaher)."

Why this stark asymmetry? If a chest carried by four men can cast an ohel over a corpse—causing utensils resting on top of the chest to become defiled, and vice versa—it clearly possesses the physical dimensions of an ohel (a square handbreadth by a handbreadth, elevated a handbreadth off the ground; see Sukkot 16b). Why, then, can that same chest not intercept the path of impurity and protect what lies on its other side?

Terutz A: The Ontological Divide Between Physical Shadow and Legal Shelter

Rabbi Chaim Soloveitchik (Chiddushei Rabbeinu Chaim HaLevi, Hilchot Tumat Met 21) resolves this discrepancy by distinguishing between the physical act of ha'ahalah (overshadowing) and the formal designation of an ohel:

          [Tumat Ohel: Two Distinct Mechanics]
                          │
         ┌────────────────┴────────────────┐
         ▼                                 ▼
   Bringing Tum'ah                    Screening Tum'ah
   (Ha'avarat HaTum'ah)               (Chatzitzah / Hatzalah)
   --------------------               -----------------------
   • Relies on PHYSICAL canopy        • Relies on HALACHIC structure
   • Any spatial barrier of 1 tefach  • Requires permanent, fixed shelter
     conducts defilement horizontally.  (Ohel Kavu'a).
   • Keilim possess physical form.    • Keilim remain mobile, lacking
                                        inherent structural permanence.

1. For bringing impurity (le-havi et ha-tum'ah): The Torah requires only the physical reality of an overhead canopy (ohel tamtzi'uti). As long as a solid object of one handbreadth intervenes between the corpse and another utensil, it establishes a shared ceiling that conducts impurity horizontally across that space. Because a vessel or human body physically obstructs the sky and casts a physical shadow of a handbreadth, it functions as a conduit for defilement.
2. For screening against impurity (la-chotzetz bifnei ha-tum'ah): The barrier must possess the legal status of an architectural shelter (ohel torani / kavu'a). An autonomous ohel that protects its surroundings must be fixed, grounded, and non-susceptible to ritual impurity. Utensils, by their very nature, are mobile (metaltelin) and susceptible to ritual defilement (mekablin tum'ah). A mobile utensil cannot constitute an architectural dwelling. Consequently, it cannot screen against defilement unless it nullifies its mobility by attaching itself to a permanent, stationary structure—namely, im dofnot ohalim.

Terutz B: The Kal VaChomer Inversion and the Problem of Susceptibility

The Rashash (Mishnah Oholot 5:7:1) and Tosafot (Eruvin 44a s.v. Kol she-einano) emphasize that the inability of a vessel to protect stems from its intrinsic susceptibility to ritual contamination:

• A vessel is prone to becoming an Avi HaTum'ah or Rishon LeTum'ah.
• An object that can itself become defiled cannot serve as an impenetrable fortress against defilement (ein keli tamei chotzetz).
• Even when dealing with non-susceptible vessels (kelei avanim, kelei adamah), the Sages established a uniform boundary (lo pelug): an autonomous utensil remains classified under the laws of keilim, not ohalim. It spreads defilement downward because overhead coverage is defined purely geometrically, but it cannot prevent defilement from passing through its upper surface because it lacks the legal permanence of a non-utensil shelter.

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Kushya 2: Rabbi Akiva’s Screening Mechanism for the Suspended Pot

According to Rabbi Akiva, if an earthenware pot hangs from a beam, why do the vessels inside it remain pure?

If the pot does not possess an airtight seal (tzamid patil), then defilement beneath the beam should enter through its open top! If the pot does have a tzamid patil, it should protect on its own merits under the basic laws of earthenware vessels (Numbers 19:15), rendering the overhead beam entirely irrelevant!

Terutz A: Spatial Negation via Sub-Tefach Clearance

The Rashash (Mishnah Oholot 5:7:2) and Rash explain that the mishnah deals with a pot lacking a tzamid patil.

• Ordinarily, an unsealed earthenware pot exposed to defilement within an ohel immediately becomes contaminated through its interior airspace (tocho).
• However, Rabbi Akiva introduces a novel spatial mechanism: When the gap between the lip of the pot and the overlying beam is less than a handbreadth (pachot mi-tefach), that narrow clearance cannot function as an entry portal (petach) for airborne defilement.
• Under the laws of Ohalot, a passage of less than a handbreadth is considered sealed (setumah) against the lateral transfer of defilement into a protected vessel.
• Thus, the pot does not need a tzamid patil; the physical proximity of the beam negates the entrance.
• The Sages disagree: They hold that although a sub-tefach gap prevents defilement from escaping a sealed enclosure, it does not prevent defilement that already circulates beneath a shared roof (ohel ha-korah) from penetrating an open vessel, unless the vessel is physically fused to the ceiling.

Terutz B: Backside Immunity and Structural Fusion

According to Maharam of Rothenburg:

• The corpse-impurity is located strictly beneath the pot's bottom exterior, not directly beneath the beam's projecting lip.
• Because the defilement hits only the base of the pot, the pot's exterior remains clean (keli cheres eino mitamei miggabo).
• The hazard is that the beam spanning overhead might act as a unifying roof (ohel ham-mavi et ha-tum'ah), drawing defilement up from beneath the pot, carrying it horizontally along the beam, and depositing it down through the pot's unsealed opening.
• Rabbi Akiva holds that because the pot hangs within a handbreadth of the beam, we apply lavud: the pot and beam merge into a single, cohesive architectural unit. Consequently, the interior of the pot is treated as a separate, isolated room partitioned off from the under-beam area, preventing the beam from channeling impurity into the pot's interior.
• The Sages counter that lavud cannot turn a mobile vessel into a structural extension of a ceiling. The rim remains legally detached, the beam continues to act as an overhead conduit, and impurity travels over the rim and down into the pot.

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Intertext

1. Parallels in Halakhot of Sukkah and Shabbat: The Nature of Partitions

                               Cross-Tractate Conceptual Parallels
                                                │
         ┌──────────────────────────────────────┴──────────────────────────────────────┐
         ▼                                                                             ▼
  Eruvin 44a / Sukkah 16a-b                                                     Shabbat 43b / Kelim
  Mobile Partitions (Mechitzah Nayedet)                                         Tzamid Patil vs. Dofen Ohel
  -------------------------------------                                         ---------------------------
• "Mechitzah she-nas'uha bnei adam":                                          • A sealed clay vessel protects by 
  Carried partitions are invalid for Sukkah                                     virtue of its impenetrable walls.
  and Shabbat boundaries.                                                     • Mishnah Oholot reveals a secondary track:
• Matches Oholot 5:7: Keilim cannot form                                        An unsealed vessel protects if integrated
  a protective tent while carried by people.                                    into the architectural framework of an ohel.

The disqualification of human- or vessel-supported tents (adam ve-khelim na'asin ohalim) directly parallels the Talmud's treatment of dynamic enclosures in the laws of Shabbat and Sukkah:

• In Eruvin 44a, the Gemara establishes: Mechitzah she-nas'uha bnei adam, ein shemah mechitzah—a partition carried by human hands does not constitute a valid legal wall to permit carrying on Shabbat, nor can it serve as a wall for a Sukkah (Sukkot 16b).
• This matches the structural logic of Mishnah Oholot 5:7: When four individuals carry a chest over a corpse, their mobility deprives the structure of architectural permanence. It creates a physical canopy that spreads defilement (letamei), but it cannot serve as a stable boundary to shield the objects within (letaher).
• The Sukkot Connection: During the festival of Sukkot, this dynamic comes to the fore. A valid Sukkah requires a stationary dwelling (dirat keva or at least an ohel ar'ai grounded in the earth). An overturned basket or mobile chest elevated above the ground fails as a Sukkah roof if it remains defined as a keli rather than an ohel. Only when a structure is integrated into the ground or attached to permanent walls (dofnot ohalim) does it acquire the legal capacity to define the space beneath it.

2. Rabbinic Corpus & Shulchan Aruch: Doors and Windows as Dynamic Plugs

In Mishnah Oholot 6:1, the mishnah transitions from vessels to structural openings:

"If corpse-bearers were passing along a portico and one of them shut a door and locked it with a key: if the door can remain in its position on its own, it remains clean..."

This principle is codified in Shulchan Aruch, Yoreh De'ah 371:

• If a corpse is carried past an entrance, closing the door isolates the interior of the house from the defilement, but only if the door can stay shut without relying on human support.
• If the door requires someone to hold it in place against the wind, or if it is held shut by an ungrounded implement, it fails as a barrier. It is classified as an unstable plug (chatzitzah hayenah omedet bifnei atzmah), and the defilement penetrates into the house.

This requirement mirrors the rule governing the barrel of dried figs or basket of straw placed in a window:

• If the organic matter can remain upright if the surrounding frame is removed (im yekholin la'amod bifnei atzman), it ceases to be treated as loose, mobile objects.
• It is legally transformed into a structural wall that blocks the passage of defilement.
• If it would tumble upon the removal of the frame, it retains its identity as loose produce, which cannot serve as an architectural barrier against tumat met.

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Psak/Practice

                  Halachic Continuum of Vessel Annexation
                                     │
       ┌─────────────────────────────┴─────────────────────────────┐
       ▼                                                           ▼
Autonomous Vessel (Unattached)                            Architecturally Fused Vessel
• Follows Mishnah 5:7 (Ein keilim na'asin)                • Follows Mishnah 5:7 (Metzilin im dofnot)
• Cannot screen against defilement                        • Screens beneath or within
• Spreads defilement via ohel                             • Requirements: Direct contact or <1 tefach,
                                                            affixed to a domestic/dwelling wall

In the codification of these laws (Rambam, Hilchot Tumat Met 21:1–6; Shulchan Aruch, Yoreh De'ah 369–372), the halacha governs modern issues of tumat kohanim:

1. Halachic Ruling on R. Akiva vs. Chachamim

The halacha follows the Sages: A vessel hanging from a beam or suspended adjacent to an exterior wall does not protect the items inside or beneath it unless its rim is flush with the overhead structure. A gap of less than a handbreadth (pachot mi-tefach) does not invoke lavud to shield an open vessel from overhead defilement.

2. Criteria for Screening with Architectural Walls (Dofnot Ohalim)

To deploy a non-susceptible vessel or covering to prevent the transmission of tum'at ohel, three conditions must be met:

1. Dwelling Status (Dofen Bayit): The wall must belong to an enclosed structure built for human shelter. Walls of courtyards, corrals, or gardens (kotel chatzer ve-ginah) are disregarded.
2. Physical Integration: The vessel must be supported by pegs or brackets fixed directly into the wall, or its rim must rest flush against the wall's surface without a lateral gap of a handbreadth.
3. Internal Dimension: The vessel must possess an internal cavity with a depth and width of at least one handbreadth (rum tefach), thereby providing the minimum space required to establish an ohel.

3. Contemporary Application: Kohanim in Contemporary Enclosures

These principles directly govern the status of kohanim in hospitals, airplanes, and enclosed public walkways:

• Hospital Corridors & Porticos: When a deceased individual is present in a hospital wing, an open or unlatched fire door does not shield adjoining rooms. Under the rule of Mishnah Oholot 6:1, a door protects the adjacent rooms only if it is closed and capable of remaining latched on its own (omedet bifnei atzmah).
• Kohanim on Airplanes: Responsa literature (e.g., Minchat Yitzchak 8:126; Tzitz Eliezer 12:62) analyzes whether an airplane flying over a cemetery conveys defilement to kohanim aboard. An airplane is a mobile vessel (keli). Because ein keilim na'asin ohalim letaher, does the aircraft fail to screen the passengers from the graves beneath it? The consensus permits travel by ruling that the airplane’s fuselage is not acting as an ad-hoc screen (chatzitzah) over an active grave; rather, the grave's impurity cleaves directly upward (tum'ah rotzetzet boka'at ve'olah) through open space, and the metal cabin functions as an enclosed, independent domain (ohel bifnei atzmo) that isolates its interior from exterior fields of defilement.

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Takeaway

A vessel cannot autonomously conquer space to screen against defilement; it can only project the protective power of an ohel when structurally subsumed into an extant dwelling. Pure mobility spreads impurity, but only stable, fixed architecture has the power to hold it at bay.