Thursday, Jul 18, 2024

Halacha Talk- Explaining Contemporary Tumah Issues

Question #1: Interruptions

When is it good to interrupt?

Question #2: Flying through Air

Is an entertainer swinging from a flying trapeze an ohel?

Question #3: Ohel Zoruk

Why would anyone throw a tent?

Question #4: Carbon Fiber versus Titanium

What difference does it make halachically whether an airplane is manufactured from aluminum, titanium or carbon fiber?


This week’s parsha teaches that a kohen may not become tomei to a human cadaver, with the exception of immediate relatives: his parents, wife, brothers, children, and sisters who never married. Kohanim know to be careful regarding funerals, not to walk under trees that overhang cemeteries and are vigilant regarding other situations that could make them tomei. However, there is less knowledge about many important situations. For example, there is much halachic discussion germane to whether an airplane flying over a cemetery or a meis aboard an airplane creates problems for a kohen. As always, it is not the purpose of this article to answer each person’s questions; that is the responsibility of the individual’s rov or posek. Our purpose is to provide halachic background.

The laws of tumas ohel, which I will define shortly, are taught at the beginning of parshas Chukas. Technically, these are not laws germane exclusively to kohanim, but are a subset of the laws of tumas meis, the laws of tumah that result from contact with a dead person. For our purposes, I will subdivide the laws of tumas meis into four general categories:

  1. Maga

This is tumah spread through physical, tactile contact. This method of spreading tumah is not unique to tumas meis, but applies to all tomei sources including neveilah, dead animals, sherotzim, certain varieties of dead small creatures and people who contract tumah (see Keilim 1:1). However, a kohen is not prohibited to become tomei because of either neveilah or sherotzim, and, therefore, the laws of these tumos are, for the most part, not germane to us until we again have korbanos, the Beis Hamikdosh and the ashes of parah asumah.

  1. Masa

Tumas masa is generated when a person lifts the tomei item. This is also not limited to tumas meis, but applies to most varieties of tumah (see Keilim 1:2). Perhaps the most common case today of becoming tomei through tumas neveilah is someone who lifts or moves a non-kosher piece of meat in a supermarket. Since the animal was not killed by shechitah, the meat is neveilah and therefore, tomei. Someone who moves the neveilah becomes tomei, even if he did not touch the meat itself, but only lifted or moved the package.

  1. Ohel

Ohel literally means tent, but tumas ohel means tumah from a meis that spreads underneath an extended roofed area and thereby conveys tumah to any person or vessel that is also under the extended ohel area. This will be the main topic of this article.

  1. Other related tumah considerations

There are various other categories of tumas meis, such as golel, dofek, kever, kever sasum, and cherev harei hu kecholol, each of which has its own, highly detailed laws that I will not be discussing in this article. Most of these, golel, dofek, kever, and kever sasum, concern either parts of a grave, or different methods of burial. Cherev harei hu kecholol is a type of tumas meis conveyed via items (according to many rishonim, only metal items) that, themselves, contracted tumah via a meis. Most rishonim rule that the prohibition of a kohen contracting tumas meis does not include coming in contact with cherev harei hu kecholol (see Tosfos, Nazir 54b).


Although the word ohel translates as “tent,” or “roof,” tumas ohel has much broader connotations and is conveyed via almost any item that covers at least a tefach (about three inches) cubed, regardless of how high it is above the meis or above the kohen. A ledge of a building, an umbrella, or a branch that are a tefach wide and overhang a grave or corpse convey tumah onto anyone or any vessel susceptible to tumah positioned directly beneath the ohel. Tumas ohel spreads from one ohel area to any other ohel that overlaps or connects, even if the different ohel “roofs” are of very different heights. It also spreads from one area to another adjacent area through an open door, window or other break in a wall, even if it is as small as a tefach by a tefach. Thus, a series of overlapping or connecting roofs, ledges, caves, umbrellas, tree branches or even people, can create a continuous ohel that transfers tumah for great distances. Indeed, that which appears to be separate buildings or structures may be one large ohel connected by open doors and windows (under certain circumstances, even through closed ones), ledges or tunnels, and tumah in one building may spread across an entire complex of buildings. This is particularly common in hospitals, museums, shopping malls, university campuses and airport terminals, where human remains in one building may spread tumah throughout the entire complex or airport, notwithstanding that those complexes appear to be several separate buildings, via interconnecting tunnels or other passageways.

An airplane that is partly over a grave or meis and partly over a branch, umbrella or person will also convey tumas ohel. We will soon discuss if this is so only if the airplane is stationary or, even if it is in flight.

In the modern world, numerous teshuvos have been published discussing whether tumas meis extends to an entire train or vehicle, when part of it passes through a cemetery or under a tree that overhangs a cemetery (see, for example, Shu’t Maharam Schick, Yoreh Deah #353; Shu’t Birchas Retzei #12; Shu’t Melamed Leho’il 2:133 and in many more recent publications). Responsa concerning whether a kohen may fly in an airplane whose route takes it over graves or cemeteries appeared as early as the 1930s, in the very infancy of commercial air travel.

Many common situations can create a halachic problem for a kohen, because of the laws of tumas ohel. For example: someone carrying human remains into an airport terminal or medical facility that connects to a subway station could convey tumah throughout the entire subway system and prohibit any kohen from remaining anywhere in the subway, since the entire system qualifies as one large ohel. Therefore, someone dying in a Bronx subway station contaminates a kohen awaiting his commuter train in Penn Station! These more complicated ohel situations can be easily rectified during construction or refurbishing of the buildings – however, they require input of a knowledgeable expert in these matters to explain how to avoid the problems. There are hospitals in Israel in which these tumah problems were rectified, because care was taken during renovation to consult rabbinic authorities how to remedy the problem.

This article will be discussing tumas ohel as spread through keilim, which I will translate loosely, but not that accurately, as “vessels,” and an important concept of tumas ohel called chatzitzah, blocking or interrupting tumah.

Blocking tumah

Although tumas meis spreads throughout the building in which it exists or spreads, it usually does not spread through the ceiling of the room in which it is located. These halachos are derived from the posuk in parshas Chukas (19:14) that implies that although tumah spreads throughout the roofed area in which it is currently found, it is blocked from spreading above, below, or outside that ohel area, including through its ceiling (Ohalos, Chapter 9).

There are three ways that to provide a barrier to block tumah:

  1. Having in item situated above the tumah, so that the tumah does not penetrate above and through it.
  2. Having an item situated below the tumah, stopping the tumah from penetrating below and through it.
  3. Closing an opening in a room or building, thus preventing tumah from moving laterally from one roofed area to an adjacent area.

What blocks tumah

As a rule of thumb, anything that is not mekabel, susceptible to, tumah will be able to block tumah. What materials are mekabeil tumah? Most utensils, defined here as receptacles that can contain an item, are divided into several categories for the purposes of tumah and taharah depending on the type of material of which they are manufactured. Germane to our discussion are the following three categories:

  1. Never mekablei tumah

Materials that do not become tomei. Indeed, there are many such materials. In the time of the Mishnah, these included most unfired vessels made of earth and those made of stone. According to many authorities, these would, today, include vessels made of plastic materials and, potentially, might include materials made of carbon fiber and fiberglass.

  1. Always mekablei tumah

There are materials that become tomei when they are complete utensils, regardless of their size. In general, metal items, or at least those made of the six metals mentioned in Chumash as susceptible to tumah — gold, silver, copper, iron, tin and lead (Bamidbar 31, 22). Steel, the most common metal used today in manufacture, is predominantly iron, and the Mishnah implies that an alloy would be treated as its majority constituent (Keilim 11:4). Thus, although there are hundreds of varieties of steel containing a wide variety of other components, for halachic purposes, steel is considered iron. Similarly, both bronze, an alloy of predominantly copper with tin, and brass, an alloy of predominantly copper with zinc, are halachically treated as copper, and pewter, an alloy of predominantly tin with either lead or antimony, is considered tin. Therefore, items made of steel, bronze, brass or pewter all become tomei and do not block tumah.

  1. Depends on size

This category consists of materials that become tomei when they are manufactured into small vessels, but do not become tomei when manufactured into large vessels, which are not meant to be moved when full. For these purposes, a “large vessel” is defined as one that can hold sixty se’ah, which by my estimate is between 150-250 gallons. (For comparison purposes, a standard wine barrel holds 31.5 gallons.) This category includes wood and most natural cloth.


At this point, we are in a position to appreciate our opening question: “When is it good to interrupt?”

The answer is when we are interrupting tumah, i.e., blocking tumah so that an adjacent area will not be forbidden for kohanim to enter, it is definitely a welcome action. A vessel made from material in category A or a large item in category C can serve as a tumah blocker.

With the greatest of ease

Does the daring young entertainer swinging from a flying trapeze qualify as an ohel?

The Mishnah states: “The following items neither convey tumah nor block it… someone jumping from one spot to another, a bird flying overhead, a garment fluttering in the breeze, or a boat sailing on the water” (Ohalos 8:5). The reason why tumah does not spread underneath the person, bird, garment or boat is because it is not at rest, unlike an ohel (Sefer Hayashar #275). Thus, the daring young man on the flying trapeze does not qualify either as an ohel to convey tumah or as an interrupter to block it. (Of course, all this is germane only if he is flying outdoors on his trapeze, and the meis is not underneath any other ohel. Otherwise, the building or “big tent” convey tumas ohel.) However, should you tie down the garment or chain the boat in place, it becomes an ohel and spreads tumah underneath itself and contaminates anything both above and below itself (see Ohalos, Chapter 9).

Ohel zoruk

Let us now explore the third of our opening questions: Why would anyone throw a tent?

Allow me to introduce a concept called ohel zoruk, which literally translates as a “thrown tent,” and is the subject of a dispute between the tanoim, Rebi and Rabi Yosi berabi Yehudah. Rebi asserts that an ohel zoruk, a moving ohel, such as a large cabinet being transported by animals, does not block tumah, whereas Rabi Yosi berabi Yehudah rules that it does (Eruvin 30b; Chagigah 25a; Nazir 55a; Gittin 8b). Their dispute is germane to the use of a large vessel [category C above], which is not mekabeil tumah, and therefore can potentially block tumah. If such a vessel is stationary, all agree that it does block tumah; the dispute between Rebi and Rabi Yosi berabi Yehudah concerns whether it blocks tumah if it is moving. According to several early acharonim, their dispute is germane only to a rabbinic issue. In the opinion of these poskim (Shu’t Shevus Yaakov, Yoreh Deah 1:85 and 2:88, Pnei Yehoshua, Sukkah 21a s.v. Uve’ikar), all tanoim agree that an ohel zoruk blocks tumah, min haTorah. The dispute between Rebi and Rabi Yosi berabi Yehudah is whether Chazal made a takanah that ohel zoruk does not block tumah, Rabi Yosi berabi Yehudah contending that they did and Rebi contending that they did not.

Aluminum, titanium, zinc and chrome

The entire discussion regarding whether airplanes can block tumah is only if we assume that they are not mekablei tumah (see Ohalos 2:1). To clarify this topic, we need to analyze yet another major issue. What is the halachic status, germane to the laws of tumah and taharah, of metals that have been discovered since the times of Chazal, which include zinc, chrome, manganese, nickel, magnesium, platinum, aluminum, titanium and many others? The Tiferes Yisroel assumes that they have the same halachic status as the six metals mentioned in Chumash, and therefore they are mekablei tumah min haTorah (Yevakeish Daas #44). As such, they could never block tumah, as I explained. However, there are poskim who dispute the conclusion of the Tiferes Yisroel and contend that only the six types of metal that the Torah mentions spread tumah, and not any of the newly discovered ones (Shu’t Igros Moshe, Yoreh Deah 2:164; Sefer Tevilas Keilim page 243). We should also note that Rav Avrohom Shaag, the rebbi of Rav Yosef Chaim Sonnenfeld, seems to hold that all these materials will be mekablei tumah miderabbanan, which would also preclude their blocking tumah (Shu’t Ohel Avraham #24).

The primary metals used for airplane manufacture today are aluminum and titanium. Only small amounts of steel are used, since it is very heavy. Most of our readers are familiar somewhat with steel and aluminum, but not with titanium, which is almost as strong as steel, but is much lighter and is very heat and corrosion resistant. The Lockheed SR-71 Blackbird, the world’s fastest jet-propelled aircraft, is made of titanium. The Boeing 747 is made predominantly of aluminum. Newer aircraft are being made from composite materials, such as graphite-epoxy, also called carbon fiber, which are very strong, but much lighter than titanium or aluminum. These lightweight materials are becoming more popular. More than half of the materials used to make the Boeing 787 Dreamliner are composites, which are also called carbon fibers.

Carbon fiber versus titanium

At this point, it is appropriate to discuss the last of our opening questions: “What difference does it make, halachically, whether an airplane is manufactured from aluminum, titanium or carbon fiber?

Assuming that we rule that the entire airplane is considered one item for kabolas tumah purposes, and that 51% of the component materials of an airplane determine whether it is mekabeil tumah or not (see Keilim 11:4, see also Keilim 13:6), booking a flight on a Dreamliner manufactured from carbon fiber might have more potential resolutions to our halachic issues than one manufactured from titanium or aluminum. However, since I am aware that there are rabbonim who dispute both of these conclusions, I will simply instruct our local kohen to discuss this question with his posek.





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