"Duck and cover" is a method of personal protection against the effects of a nuclear explosion. Ducking and covering is useful in offering a degree of protection to personnel located outside the radius of the nuclear fireball but still within sufficient range of the nuclear explosion that standing upright and uncovered is likely to cause serious injury or death. In the most literal interpretation, the focus of the maneuver is primarily on protective actions one can take during the first few crucial seconds-to-minutes after the event, while the film of the same name and a full encompassing of the advice also cater to providing protection up to weeks after the event.
The countermeasure is intended as an alternative to the more effective target/citywide emergency evacuation when these crisis relocation programs would not be possible due to travel and time constraints. Maneuvers similar, but not identical, to Duck and Cover are also taught as the response to other sudden destructive events, such as an earthquake or tornado, in the comparable situation where preventive emergency evacuation is similarly not an option, again, due to time constraints. In these analogously powerful events, Drop, Cover and Hold on likewise may help prevent injury or death if no other safety measures are taken.
Procedure
During a surprise nuclear attack
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.
When warning is given Under the conditions where some warning is given, one is advised to find the nearest bomb shelter, or if one could not be found, any well-built building to stay and shelter in place. Sheltering is, as depicted in the film, also the final phase of the "duck and cover" countermeasure in the surprise attack scenario.
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,Ruffman, Alan and Howell, Colin D. (edited by). Ground Zero: A Reassessment of the 1917 Explosion in Halifax Harbour (1994, Nimbus Publishing), p.276. 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",http://www.gensuikin.org/english/photo.html Photographs of Hiroshima and Nagasaki 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. This response was also observed among people in the vicinity of Hiroshima and Nagasaki.
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-oriented 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