duck and cover

Procedure

During a surprise nuclear attack

Dropping immediately and covering exposed skin provide[s] protection against blast and thermal effects ... Immediately drop facedown. A log, a large rock, or any depression in the earth's surface provides some protection. Close eyes. Protect exposed skin from heat by putting hands and arms under or near the body and keeping the helmet on. Remain facedown until the blast wave passes and debris stops falling. Stay calm, check for injury, check weapons and equipment damage, and prepare to continue the mission.

Immediately after one sees the first flash of intense heat and light of the developing nuclear fireball, one should stop, get under some cover and drop/duck to the ground. There, one should assume a prone-like position, lying face-down, and to afford protection against the continuing heat of the explosion further cover exposed skin and the back of one's head with one's clothes; or, if no excess cover or cloth is available, one should cover the back of one's head and neck with one's hands.

Similar instructions, as presented in the Duck and Cover film, are contained in the British 1964 public information film Civil Defence Information Bulletin No. 5 and in the 1980s Protect and Survive public information series. Children in the Soviet Union likewise received almost identical classes on countermeasures, according to Inside the Kremlin's Cold War authors Zubok and Pleshakov.

In U.S. Army training, soldiers are taught to fall down immediately and cover their face and hands in much the same way as is described above.

In the classroom scene of the film, the rapid employment of school desks, as an improvised shelter following the awareness of the initial light flash, is a countermeasure primarily to offer protection from potential ballistic window glass lacerations when the slower moving blast wave arrived. However, in higher blast pressure zones, where partial-to-total building collapse may occur, it would also serve a similar role to that borne out from experience in urban search and rescue, where voids under the debris of collapsed buildings are common places for survivors to be found. More rigid examples of void-forming-tables to shelter under include the "Morrison indoor shelter", which was widely distributed by the millions in Britain as a protective measure against building collapse, brought about by blast pressures generated during the conventional bombing of cities in World War II.

Cursory analysis

The "duck and cover" countermeasure could save thousands. This is because people, being naturally inquisitive, would instead run to windows to try to locate the source of the immensely bright flash generated at the instant of the explosion. During this time, unbeknownst to them, the slower moving blast wave, would be rapidly advancing toward their position, only to arrive and cause the window glass to implode, shredding onlookers. In the testimony of Dr. Hiroshi Sawachika, although he was sufficiently far away from the Hiroshima bomb himself and was not behind a pane of window glass when the blast wave arrived, those in his company who were had serious blast injury wounds, with broken glass and pieces of wood stuck into them.

During earthquakes and tornadoes

Similar advice to "duck and cover" is given in many situations where structural destabilization or flying debris may be expected, such as during an earthquake or tornado. At a sufficient distance from a nuclear explosion, the blast wave produces similar results to these natural phenomena, so similar countermeasures are taken. In areas where earthquakes are common, a countermeasure known as "Drop, Cover, and Hold On!" is practiced. Likewise, in tornado-prone areas of the United States, especially those within Tornado Alley, tornado drills involve teaching children to move closer to the floor and to cover the backs of their heads to prevent injury from flying debris. Some US states also practice annual emergency tornado drills.

History

The dangers of viewing explosions behind window glass were known of before the Atomic Age began, being a common source of injury and death from large chemical explosions. The Halifax Explosion of 1917, an ammunition ship exploding with the energy of roughly 2.9 kilotons of TNT, injured the eyes and faces of hundreds of people who stayed behind and looked out of their windows after seeing a bright flash, with 200 blinded by broken glass when the slower moving blast arrived. Every window in the city of Halifax, Nova Scotia, was shattered in this catastrophe of human error.

In the Record of the "Nagasaki A-bomb War Disaster", those close to the hypocenter (Matsuyama township), were described as all having been killed, with the exception of "a child who was in an air-raid shelter." A little further away, Professor Seiki of Nagasaki Medical School Hospital was building an air-raid dugout 400 m from the hypocenter of the detonation and survived. Chimoto-san, who was atop a distant hill that creates the valley in which Nagasaki is located, performed the similar "hit the deck" maneuver upon seeing the bomb drop, which was notably prior to the detonation. However despite having these few seconds of relatively unique warning, he did not stay on the ground for long enough after the flash subsided, and received some translational injuries due to prematurely standing-up again, at which point the slower moving blast wave swept past him and carried him with it for a few meters.

According to the 1946 book Hiroshima and other books which cover both bombings, in the days between the atomic bombings of Hiroshima and Nagasaki, some survivors of the first bombing went to Nagasaki and taught others about ducking after the atomic flash and informed them about the particularly dangerous threat of imploding window glass. As a result of this and other factors, far fewer died in the initial blast at Nagasaki as compared to those who were not taught to duck and cover. The general population however was not warned of the heat or blast danger following an atomic flash, due to the new and unknown nature of the atomic bomb. Many people in Hiroshima and Nagasaki died while searching the skies, curious to locate the source of the brilliant flash.

When people are indoors, running to windows to investigate the source of bright flashes in the sky still remains a common and natural response to experiencing a bright flash. Thus, although the advice to duck and cover is over half a century old, ballistic glass lacerations caused the majority of the 1000 human injuries following the Chelyabinsk meteor air burst of 15 February 2013.

Background

The United States' monopoly on nuclear weapons was broken by the Soviet Union in 1949 when it tested its first nuclear explosive, the RDS-1. With this, many in the US Government, as well as many citizens, perceived that the United States was more vulnerable than it had ever been before. In 1950, during the first big Civil Defense push of the Cold War—and coinciding with the Alert America! initiative to educate Americans on nuclear preparedness, the adult-orientated Survival Under Atomic Attack was published. It contains "duck and cover" or more accurately, cover and then duck advice without using those specific terms in its Six Survival Secrets For Atomic Attacks section. 1. Try to Get Shielded 2. Drop Flat on Ground or Floor 3. Bury Your Face in Your Arms ("crook of your elbow"). The child-oriented film Duck and Cover was produced a year later by the Federal Civil Defense Administration in 1951.

"Duck and cover" exercises quickly became a part of Civil Defense drills that every US citizen, from children to the elderly, was encouraged to practice so that they could be ready in the event of nuclear war.

Education efforts on the effects of nuclear weapons proceeded with stops-and-starts in the US due to competing alternatives. In a once classified, 1950s era, US war game that looked at varying levels of war escalation, warning and pre-emptive attacks in the late 1950s early 1960s, it was estimated that approximately 27 million US citizens would have been saved with civil defense education. At the time however the cost of a full-scale civil defense program was regarded as lesser in effectiveness, in cost-benefit analysis than a ballistic missile defense (Nike Zeus) system, and as the Soviet adversary was believed to be rapidly increasing their nuclear stockpile, the efficacy of both would begin to enter a diminishing returns trend. When more became known about the cost and limitations of the Nike Zeus system, in the early 1960s the head of the department of defense under president John F. Kennedy,

Robert McNamara, determined the ineffectiveness of the Nike-Zeus system, especially in its benefit-cost ratio compared to other options. For instance, fallout shelters would save more Americans for far less money.

Efficacy during a nuclear explosion

Within a considerable radius from the surface of the nuclear fireball, 0–3 kilometers—largely depending on the explosion's height, yield and position of personnel—ducking and covering would offer negligible protection against the intense heat, blast and prompt ionizing radiation following a nuclear explosion. Beyond that range, however, many lives would be saved by following the simple advice, especially since at that range the main hazard is not from ionizing radiation but from blast injuries and sustaining thermal flash burns to unprotected skin. Furthermore, following the bright flash of light of the nuclear fireball, the explosion's blast wave would take from first light, 7 to 10 seconds to reach a person standing 3 km from the surface of the nuclear fireball, with the exact time of arrival being dependent on the speed of sound in air in their area. The time delay between the moment of an explosion's flash and the arrival of the slower moving blast wave is analogous to the commonly experienced time delay between the observation of a flash of lightning and the arrival of thunder during a lightning storm, thus at the distances that the advice would be most effective, there would be more than ample amounts of time to take the prompt countermeasure of 'duck and cover' against the blast's direct effects and flying debris. For very large explosions it can take 30 seconds or more, after the silent moment of flash, for a potentially dangerous blast wave over-pressure to arrive at, or hit, one's position.

Blast effects

To elucidate the effects on lying flat on the ground in attenuating a weapons blast, Miyoko Matsubara, one of the Hiroshima maidens, when recounting the bombing in an interview in 1999, said that she was outdoors and less than 1 mile from the hypocenter of the Little Boy bomb. Upon observing the nuclear weapons silent flash she quickly lay flat on the ground, while those who were standing directly next to her, and her other fellow students, had simply disappeared from her sight when the blast wave arrived and blew them away.

Position of the body can have a considerable influence in protection from blast effects. Lying prone on the ground will often materially lessen direct blast effects because of the protective defilade effects of irregularities in the ground surface. Ground also tends to deflect some of the blast forces upward. Standing close to a wall, even on the side from which the blast is coming, also lessens some of the effect. Orientation of the body also affects severity of the effect of blast. Anterior exposure of the body may result in lung injury, lateral position may result in more damage to one ear than the other, while minimal effects are to be anticipated with the posterior surface of the body (feet) toward the source of the blast.

The human body is more resistant to sheer overpressure than most buildings, however, the powerful winds produced by this overpressure, as in a hurricane, are capable of throwing human bodies into objects or throwing debris at high velocity, both with lethal results, rendering casualties highly dependent on surroundings. For example, Sumiteru Taniguchi recounts that, while clinging to the tremoring road surface after the Fat Man detonation, he witnessed another child being blown away, the destruction of buildings around him and stones flying through the air. Similarly, Akihiro Takahashi and his classmates were blown by the blast of Little Boy by a distance of about 10 meters, having survived due to not colliding with any walls etc. during his flight through the air. Likewise, Katsuichi Hosoya had a near identical testimony.

During the 2013 Chelyabinsk meteor explosion, a fourth-grade teacher in Chelyabinsk, Yulia Karbysheva, saved 44 children from potentially life-threatening ballistic window glass cuts by ordering them to hide under their desks when she saw the flash. Despite not knowing the origin of the intense flash of light, she ordered her students to execute a duck and cover drill. Ms. Karbysheva, who herself did not duck and cover but remained standing, was seriously lacerated when the explosion's blast wave arrived, and window glass blew in, severing a tendon in one of her arms; however, not one of her students, who she ordered to hide under their desks, suffered a cut. A follow-up study of the effects of the meteor airburst determined that the windows most prone to breaking when exposed to a blast overpressure are those of school buildings, which tend to be large in area.

Flash & burn injuries

The advice to cover one's exposed skin with anything that can cast a shadow, like the picnic blanket and newspaper used by the family in the film, may seem absurd at first when one considers the capabilities of a nuclear weapon. However, even the thinnest of barriers such as cloth or plant leaves would reduce the severity of burns on the skin from the thermal radiation with the flash light, similar in average emission spectrum/color to sunlight. The thermal radiation emits in the ultraviolet, visible light, and infrared range but with a higher light intensity than sunlight, and this combination of light rays is capable of delivering radiant burning energy to exposed skin areas. As the time-to-rise at peak and total duration of the emittance pulse of this burning thermal radiation is both prolonged and increases with larger explosive yield, it is usually at least a few seconds long for all high yield stockpiled weapons, creating the potential for protective countermeasures.

High importance is given to closing eyelids and covering the eyes as temporary or permanent flash blindness is a risk potential without this covering, especially at night.

A photograph taken about 1.3 km from the hypocenter of the Hiroshima bomb explosion showed that the shadowing effect of leaves from a nearby shrub protected a wooden utilities pole from charring discoloration due to the burst of thermal radiation; the rest of the telephone pole, which was not under the protection of the leaves, was charred almost completely black. The difference in required flash-energy necessary to produce essentially immediate, though transitory, non-propagating flaming, and that required to achieve a continued self-sustained propagating flaming are orders of magnitude in difference for most combustible materials. In the case of untreated timber it is largely dependent on the depth of char. While the propagating fires in both Japanese cities were almost exclusively ignited by the blast wave overturning charcoal cooking-braziers and similar secondary events, thermal flash-fires from untreated fabric and timber in the urban environment is considered potentially the widest destructive effect of the higher yield explosive devices.

The Nevada test site used for testing nuclear devices had a dry desert environment with low humidity, which repeatedly demonstrated the flash-combustion effect during tests. Many investigative films made on location there, such as The House in the Middle and others, focused on the combustion of fabrics and clothing.

Initial nuclear radiation

While not designed for those faced with low-yield neutron bombs or for those who are, in general, so close to the nuclear fireball that prompt/initial radiation would be life-threatening in the short-medium term, ducking and covering would nevertheless slightly reduce exposure to the initial gamma rays, specifically the portion emitted after the first flash of visible light. The initial gamma rays are defined as those emitted from the fireball & following mushroom cloud which can reach personnel on the ground for a total of approximately 1 minute, at which point the intensity of the radiation has diminished and the atmosphere itself is thick enough to act as full shielding.

As approximately half of these gamma rays are emitted in the first second and the other half, over the following 59 alongside gamma rays being mostly emitted in a straight line, people lying on the ground will more likely have obstacles serving as radiation protection such as building walls, foundations, car engines, etc. between their bodies and the radiation emitted from both the fireball and the accompanying lower levels of radiation that continue to arrive at the ground for about 1 minute, during the mushroom cloud phase, which is termed "cloudshine". It would also give protection from the even smaller fraction of radiation that changes direction and is randomly reflected and scattered by the air/"skyshine". Approximately "One and one half inches"/37 mm of steel will reduce gamma dose by half. Its half-value thickness.

The effective gamma ray energy of the cloudshine is not especially high, 200 KeV.

Unlike the relatively low-yield, or low explosive energy "A-bombs" dropped on Hiroshima and Nagasaki, which did result in a sizable proportion of injuries from prompt radiation, higher yield "hydrogen bombs" (thermonuclear weapons) are not expected to result in very many such injuries – as the range at which the ionizing radiation from higher yield devices is of primary concern, is already well inside the hyper-lethal blast and flash burn areas.

Delayed nuclear radiation, "fallout"

Apart from the intrinsic "prompt effects" of nuclear detonations, that of thermal flash, blast and initial radiation releases, if any part of the fireball of the nuclear detonation contacts the ground, in what is known as a surface burst, another, comparatively slowly increasing, radiation hazard will also begin to form in the immediate area.

Putting aside the possibility of the detonation occurring during an already established heavy rain-storm, the formation of this life-threatening "delayed nuclear radiation" manifests only when the altitude, or "height of burst" of the explosion, is such that both the fireball and the buoyant updrafts it creates, sufficiently heats and lifts the soil that was below it into the core of the mushroom cloud. Once there, the very hot radioactive isotope products of the nuclear reactions that produced the explosion, begin to coalesce with the cooler and denser soil. Upon cooling, this mixture begins to locally fall-out or precipitate-out of the mushroom cloud, falling back to the surface of the earth, near to the point of detonation, over the next few minutes and hours.

While the duck and cover countermeasure, in its most basic form, offers a small to negligible protection against fallout, the technique assumes that after the effects of the blast and initial radiation subside, with the latter of which being no longer a threat after about "twenty seconds" to 1 minute post detonation, a person who ducks and covers will realize when it is wise to cease ducking and covering (after the blast and initial radiation danger has passed) and to then seek out a more sheltered area, like an established or improvised fallout shelter to protect themselves from the ensuing potential local fallout danger, as depicted in the film.

After all, "Duck and Cover" is a first response countermeasure only, in much the same way that "Drop, Cover and Hold On" is during an earthquake, with the advice having served its purpose once the earthquake has passed, and possibly other dangers—like a tsunami or fallout—may be looming, which then require movement to high ground and radiation protection, respectively.

However, if such a shelter is unavailable, the person should then be advised to follow the Shelter in Place protocol, or if given, emergency evacuation advice. Evacuation orders would entail exiting the area completely by following a path perpendicular to the wind direction and therefore perpendicular to the path of the fallout plume. Taking upper atmospheric winds into account, surface winds alone are not to be depended upon as indicative of the direction of fallout movement. "Sheltering in place" is staying indoors, in a preferably sealed tight basement, or internal room, for a number of hours, with the oxygen supply available in such a scenario being more than sufficient for 3+ hours in even the smallest average room, under the assumption that the improvised seal is perfect, until carbon dioxide levels begin to reach unsafe values and necessitate room unsealing for a number of minutes to create a room air change.

Nuclear electromagnetic pulse, non-lethal

In respect to the other non-lethal weapon effects from an IND detonated on or near the surface, the detonation's blast wave would likely produce a momentary electric grid blackout due to the loss of a large portion of a city's electrical equipment drawing power/electrical load, while the electromagnetic pulse (EMP) from a surface/ground-burst explosion would cause little damage outside the blast area, so cell phone towers that survive the blast should be capable of carrying communications. But if communications during the 9/11 attacks or after a major hurricane are anything to go by and the cell phone network towers survive, the service would be overloaded (a mass call event) and thereby made useless soon after; however, if prior arrangements between the cell network and emergency responders are made to give them priority and bar access to all other individuals, then it may be an effective service.

The Civil Defense (CD) shelters, as depicted in the film, were stocked for such an eventuality. They contained among other things, at least one ruggedized CDV-715 radiation survey meter and one CD emergency radio receiver which would respectively be used to facilitate a safe delayed evacuation, regardless of outside help though if communications continued, the radio receiver was to inform them of the outside situation as it developed.

Long-term survival

The dubious assumption that "only the cockroaches" would survive the post-war fallout environment was frequently used in an attempt to criticize Duck and Cover during the height of the Cold War, contextually at a time when discussion of a total war involved the much greater US-Soviet arsenal of nuclear weapons that were then in existence. However even at that time, this assumption was shown to be misled, as scientifically detailed in areas including the 1988 book Would the Insects Inherit the Earth and Other Subjects of Concern to Those Who Worry About Nuclear War.

In material terms, the primary life-threatening risk survivors and downwinders could face in the long-term after a nuclear explosion or war, is the "nuclear famine" issue, the potential continuation of hostilities by conventional warfare and radioactive contamination of the food and water supplies, disrupting the normal distribution and consumption, of these vital goods.

Cold War continuity of government planners and civil defense organizations in general have always had this disruption, or "nuclear famine" issue in mind, as widespread infrastructure destruction producing starvation conditions was also seen during and after WWII. Papers such as On Reorganizing After Nuclear Attack, and Survival of the relocated population of the U.S. after a nuclear attack by Nobel Prize winner, Eugene Wigner, detail the thought and attention that went into long-term survival, relocation and reconstruction.

Numerous human and agricultural decontamination countermeasures exist for the two most persistent and biologically significant isotopes, cesium-137, strontium-90 and long-lived fallout contamination in general, with the most visible and immediate act that will prevent a potentially large dose to the public, taking the form of using shielded bulldozers to skim off the layer of topsoil that the fallout had settled on, a restorative practice that was fielded upon the creation of Lake Chagan. The creation of human decontamination tents at the entrances of buildings and when lower levels of risk exist, the use of clean room air showers as a form of contamination control to prevent the spread of radionuclides that adhere to dust, into building interiors, would also be advisable to reduce the elevated risk of radiation induced cancer that would otherwise occur. Air showers may be paired with electrostatic precipitators to attract the dust to collection plates, forestalling a re-suspension that may otherwise be inhaled. Moreover use of the open access radioecology research on decontamination and conventional agriculture in the Chernobyl-Polesie State Radioecological Reserve and around the Fukushima accident, would both be implemented in the event of any widespread fallout contamination, with particular emphasis on bioremediation of radionuclides from soil and aquifers. Although less of a hazard than external exposure, internal decontamination, that may be required after assessment in a whole-body counting session, in the long term may, as is now, be conducted with binding-and-excretion promoting chelation therapy, with ammonium-ferric-hexacyano-ferrate (AFCF)/"Giese salt", Radiogardase and DPTA all proven effective.

Historical and psychological assessment

Some historians and documentaries, including science historian Melissa Smith in a 2010 article for The British Journal for the History of Science and the film 1982 The Atomic Cafe, have described "duck and cover" advice as propaganda.

In U.S. Army training, soldiers are taught to immediately fall down, covering face and hands in much the same way as is described by the advice to duck and cover.

The exercises of Cold War civil defense were described by historian Guy Oakes in 1994 as having less practical use than psychological use: to keep the danger of nuclear war high on the public mind, while also attempting to assure the American people that something could be done to defend against nuclear attack.

Tornadoes

Ducking and covering does have certain applications in other, more natural disasters. In states prone to tornadoes, school children are urged to "duck and cover" against a solid inner wall of a school, if time does not permit seeking better shelter—such as a storm cellar—during a tornado warning. The tactic is also widely practiced in schools in states along the West Coast of the United States, where earthquakes are commonplace. Ducking and covering in either scenario would theoretically afford significant protection from falling or flying debris.

Earthquakes

In an earthquake, which are generally of a natural tectonic plate origin (although they can be artificially generated by the detonation of a nuclear explosive device in which sufficient energy is transmitted into the ground, with an extreme case to serve as an example of this phenomenon being the Operation Grommet Cannikin test of the 5 megaton W71 warhead exploded deep underground on Amchitka Island in 1971, which produced a seismic shock quake of 7.0 on the Richter magnitude scale) people are encouraged, regardless of the cause of the quake, to "drop, cover and hold on": to get underneath a piece of furniture, cover their heads and hold on to the furniture. This advice also encourages people not to run out of a shaking building, because a large majority of earthquake injuries are due to broken bones from people falling and tripping during shaking. While it is unlikely that "drop, cover and hold on" will protect against a building collapse, in earthquake-prone areas in the United States building codes require that buildings withstand quakes up to an expected magnitude enough to allow evacuation after shaking stops. and thus a building collapse of these structures (even during an earthquake) is rare. "Drop, cover and hold on" may not be appropriate for all locations or building types, but the Red Cross advises it is the appropriate emergency response to an earthquake in the United States.