Shelter, 'mamad' or sealed room?

By GAIL LICHTMAN
The decision when and where to go in an emergency will be up to the Home Front Command and will be based on the specific type of threat facing the nation at that time. The public will receive instructions from the Home Front Command and should follow them. "With conventional weapons, the damage is a result of the blast and the impact of shell fragments," says Prof. David Yankelevsky, head of the Technion's Building Research Institute and an expert on structures subject to extreme loading. "It is necessary to have a proper envelope to withstand these if the shelter is located above ground. If the shelter is below ground, a lot of the damage is stopped by soil material, and only the shock waves travel to the shelter and affect the envelope." With respect to nuclear attack, Yankelevsky explains that there is also a blast, but it differs in signal shape and is accompanied by radiation and intense heat. Chemical and biological attacks involve contamination of the air. "When the main threat is air contamination, you don't need envelope thickness and strength as much as insulation. But you also need enough air inside for the duration of the contamination outside. Because air volume is limited, there has to be a supply of filtrated air," he notes. "Conventional attacks are instantaneous and usually do not require a prolonged stay. But even then, if there is a prolonged stay, there is a need for a supply of fresh air through ventilation or filtering." The mamad is a similar concept to the shelter. It consists of a reinforced concrete vertical shaft with access from the building's individual apartment. "The idea was to bring the shelter into the apartment," Yankelevsky says. "This was a change in concept following the First Gulf War when the warning time was shortened and there was a need for fast access to shelter. This type of vertical shaft also makes the building resistant to earthquakes by providing increased resistance to strong shaking." The sealed room is not designed to withstand blast and shell fragment impact. It was an improvisation decided upon during the First Gulf War when there was a danger of chemical attack. It provides insulation from contamination. "But it is not worth much as far as the level of protection against conventional attacks," says Yankelevsky. So what should you do if you don't have a mamad or cannot reach a shelter quickly? "Fortunately, Israeli buildings are built with reinforced concrete shells," Yankelevsky explains. "And even if they were not specifically designed to withstand blasts, reinforced concrete generally has a significant capacity to do so. In Jerusalem, there is additional protection. Most buildings are faced with natural stone, which is relatively strong and can deflect fragment impact. It is best to go into an interior room away from windows and outer walls," he suggests. What about the staircase? "The staircase is not always the best place," he says. "This depends on how it is built. If it is an exterior of the building, has windows or is made of prefabricated material only lightly connected to the rest of the building, the staircase would not be a good choice. If it is in the interior with reinforced concrete, then it may be similar to a mamad. Nevertheless, the public must listen to specific instructions given at the time by the Home Front Command and follow those."