Some tips on behavior during an explosion threat..
Petrenko Evgeny Sergeevich
SOME TIPS ON BEHAVIOR DURING AN EXPLOSION THREAT
Explosive terrorism has unfortunately become a reality today. There is no hope that this nightmare will end in the near future. It is also not yet possible to station a policeman near every forgotten bag or box or to make the entire population explosive experts.
Let's try to consider the problem and give recommendations on survival in these conditions for some groups of the population. Explosives experts, who have to search for and defuse explosive devices and other explosive objects, hopefully know their business perfectly and do not need advice. Another matter is employees of various enterprises and institutions responsible for security and safety, public transport drivers, employees of the Ministry of Internal Affairs, who, due to their job, may encounter an explosive object, not being explosives experts, and simply residents of our large and small cities, who most often suffer from terrorist attacks.
There have been many recommendations recently, and quite often such recommendations are given by “experts” after watching American action films or after thinking in the office at the table as a result of solving systems of differential equations describing the motion of planets in particularly remote metagalaxies. Although the physics of explosion is one of the most complex sciences, in which the most complex mathematical apparatus is used and the greatest minds of humanity worked, many solutions are on the surface and can be used by anyone.
Let's start from the beginning. The question can only be about some more or less significant reduction in the probability of a terrorist act or a reduction in the severity of its consequences. There are no technical means capable of providing 100% protection from terrorist acts and their consequences, and probably never will be. As funny as it may sound, the most effective and accessible way to protect against the damaging factors of an explosion (fragments, shock waves and detonation products) is protection by distance. And what is it (distance) the more the better. From a physical point of view, this is explained by the fact that the intensity of the shock wave, the density of the fragmentation flow and the speed of individual fragments decrease proportionally to the square and even the cube of the distance from the explosion site. It is known that to cause a severe concussion to a person, an excess pressure of only 0.1 atmospheres in the shock wave front is sufficient, while an excess pressure of 0.4 … 0.5 atmospheres is fatal. A fragment weighing only 0.1 g and piercing a steel sheet 1 mm thick is considered lethal. Based on this, it can be argued that each meter away from the explosion site significantly increases the chances of survival or, at least, reduces the severity of the effects of the explosion factors. In everyday language, it sounds something like this: try to stay as far away as possible from various boxes, bags, forgotten things (no matter how much you want to look into them), try not to be onlookers watching the work of searching for and defusing real explosive devices, and especially do not try to defuse anything yourself after gaining “experience” as a result of watching another action movie. There is another aspect of the effectiveness of the distance protection method. A person who is not a terrorist, but who approached a real explosive device out of curiosity and left his tracks, fingerprints or personal belongings there, or who was simply remembered by witnesses, may subsequently find it quite difficult to prove to investigators his non-involvement in the event. Although people say that curiosity is not a vice.
It is necessary to approach the recommendations of some pseudo-«experts» who advise to dodge fragments or even run for cover after an explosion. Maybe someone will succeed, but it is worth noting that the initial velocity of the shock wave during the explosion of most military and industrial explosives is more than 3000 m/s, metal fragments — from several hundred to 1500-1700 m/s. Therefore, it is almost impossible not only to hide, but even to change your position in space during the movement of these components of the explosion. Another matter is the secondary damaging factors of the explosion: glass fragments, open fire from flammable materials, smoke and especially — panic. This is a separate, rather voluminous issue that requires its own solution and is not discussed in this article yet.
Some experts recommend taking cover behind any obstacles, lying down on the floor or pressing yourself against a wall in a room when there is a risk of explosion. If the first recommendation is not subject to discussion (even clothes, especially winter clothes, can significantly weaken the impact of shrapnel, especially shrapnel on the fly), then the other two are quite controversial. And here's why. It is known that in the ground layer of air during the explosion of various explosive charges placed just above ground level, a so-called Mach shock wave is formed, the excess pressure at the front of which can exceed the similar parameter of the shock wave at other points in space by up to 2.5 times. This means that a person lying on the ground or floor is affected by a much more intense shock wave compared to a standing person removed from the explosion site at the same distance. If the shock wave only knocks over a standing person, then a lying person can get, for example, a severe concussion. It was not for nothing that during the Great Patriotic War, experienced soldiers forced inexperienced recruits to squat in a trench during artillery attacks or air bombardments, and not lie face down at the bottom of the trench, no matter how scary it was. Here it is – life experience, which can be used even now, even without knowing the physics of the process.
Now let's consider another case, when a person is recommended to press against a wall before an explosion. The case with a sliding (passing) shock wave was considered above. If the shock wave is incident (approaches the wall in a direction close to the perpendicular), then in the wall layer of air, any object is affected almost simultaneously by two identical shock waves — incident and reflected (the parameters of the latter will be closer to the parameters of the incident, the stronger, «rigider» the wall). That is, the intensity of the impact of the shock wave on a person can double. This process can be interpreted as follows. If a person is pressed several times with a finger, a bruise may appear at the point of contact. Another matter if the total impulse of the impact of several such relatively weak pressures is translated into one powerful short punch to the head. Is there a difference?
All of the above does not mean that a person facing the threat of an explosion finds himself in a hopeless situation and must meekly await his fate. As already stated, it is best to avoid exposure to an explosion altogether. But if it is impossible to avoid the event, then depending on the circumstances and the time available, the following actions must be taken:
- move as far away as possible from the location of the suspected explosive device (for information, the radius of the dispersion of steel fragments can be up to 1000 m or more);
- take cover behind local objects or in folds of the terrain (just do not try to use a glass display case or shelves with flammable substances as cover);
- if it is impossible to take cover, it is necessary to ensure a minimum body surface area in the direction of the possible arrival of the shock wave and fragments, for example, by squatting at a distance of no closer than 0.5 m from the wall and pressing your head to your knees, covering it (the head) with your own briefcase, bag, book, hands, clothes, etc.
Unfortunately, in practice there may not be time to perform such actions.
Now some additional wishes and recommendations for those who, due to their job duties, may encounter an explosive device, without being an explosive expert.
There are a number of special technical means that provide solutions to problems of searching for and defusing explosive devices. And this is a separate conversation. The possibilities of visual identification, recognition of a detected explosive device even by highly qualified specialists are very limited primarily due to the large variety of these devices, as well as due to the placement in most cases of these explosive devices in opaque bags, packages, luggage. Therefore, it would be better to assume that in this particular bag there is a real explosive device with a fragmentation casing, equipped with all known types of target sensors: a radio fuse, a clock mechanism, a self-destructor, an element of non-removability, an element of non-defusing, a tension target sensor, etc. In reality, such a combination cannot be in the fuse, and in 99 cases out of 100 there will be no explosive device itself. Nevertheless, starting your steps to fulfill your official duties, it would be more correct to proceed from the point of view of maximum security for yourself and others.
If there are special technical means – good. But what if there are none? Many actions can be performed using these recommendations and improvised means. Unfortunately, it is not yet possible to completely abandon the use of special technical means.
The first and most important thing is to stay alive (in our country only public politicians are still valued); the second is to find out, if possible, whether it is advisable or necessary to call explosive experts. You can try to call these experts every time a box, bag or empty beer can is found (in one cafe this can happen twenty times a day). They will come once or twice, and then they can send you far away: there are not that many explosive experts even in large cities, there are enough real explosive devices, but there may be problems with gasoline, transport, technical equipment and traffic jams. It may happen that they will not have time to come to a real explosive device in a given establishment after numerous previous false calls. You can try to carry out the operations to search for, identify and defuse an explosive device yourself, without having the appropriate training or the appropriate permission. In the latter case, there can be three outcomes: the first — the explosive device is found and defuses, and the winner is not put on trial (which is unlikely); the second — the explosive device went off with all the ensuing consequences; and the third — it will take a long time and, perhaps, unsuccessfully to sort out the investigation into this fact. Obviously, the real actions should lie somewhere in the middle in strict accordance with the job description. Unfortunately, there are no uniform and universal instructions on this matter yet.
Therefore, at present it seems advisable to be guided by the following. The practice of using delayed-action fuses with a clock (timer) mechanism shows that the fuse response time is set, in the overwhelming majority of cases, as a multiple of 1 hour, 30 or 15 minutes. That is, an explosion is most likely, say, at 11:30, at 12 o'clock exactly, at 9:45, etc. Accordingly, the safest time to approach the suspected explosive device is, for example, 11:37, 12:07, 9:53, etc. I hope everyone has a watch on their wrist.
It is unlikely that terrorists or killers using a radio fuse in an explosive device will try to blow up an ordinary policeman or an employee of the enterprise security service via a radio channel — such things are used to hunt larger «game». A radio fuse can be blocked with a special device — a radio fuse blocker. The use of wired explosion control lines in urban conditions in peacetime presents a number of difficulties and is therefore unlikely.
Another matter is the use of tension target sensors. In this regard, it is advisable to look carefully under your feet, paying attention even to thin nylon threads. And in no case should you «shuffle like an old man, not looking under your feet. In no case should you pull or cut the detected thread — it must simply be marked or fenced off.
It is very effective to detect an explosive device by its primary feature — explosives. Everything else (metal case, plastic parts, electronic components, mechanical watches, etc.) is secondary and may not be part of a real explosive device. Explosives can currently be detected with varying degrees of probability using various types of explosive detectors, chemical express tests or mine detection dogs (MDS).
Currently, a new technology has been developed for using small dogs to search for explosives, when the dog works in tandem with a car vacuum cleaner, which allows to significantly increase search safety, sharply reduce the time for examining buildings, structures and vehicle flows, and also increase the dog's performance in urban and industrial areas with a large number of distracting factors (oil products, paints and varnishes, noise, other animals). The best result, ensuring the maximum reliability of detecting explosives, is achieved by using several different means together. Unfortunately, the range of combat, industrial and, especially, spontaneously or systematically formed in everyday life and at work explosives is very large. Another thing is that only combat and some industrial explosives with high reliability, safety, ease of use and transportation are used to carry out terrorist acts. The number of mixed explosives is significant, but they are based on a limited range of starting materials (TNT, RDX, HMX, PETN, tetryl, ammonium nitrate), the presence of which can already be used to assess the danger of a particular substance.
No specialist will undertake to judge unequivocally whether a particular substance is explosive based on its appearance.
Explosive devices with fuses equipped with an anti-removal element, which are triggered when attempting to tilt or move the fuse, pose a serious danger. In standard engineering munitions, such elements are quite common as part of standard fuses, unlike improvised explosive devices. In order to verify the presence or absence of an explosive device with such a fuse in a suspicious object, it is necessary to perform the following actions (if specified in the job description):
- give up the idea that “I’ve always been lucky — I’ll be lucky this time”;
- do not try to pick up the object with your hands and move it to another place convenient for further inspection;
- approach the object alone in accordance with the recommendations for the optimal approach time;
- in the shortest possible time, place a light hook (wooden, plastic or, in extreme cases, aluminum, but not steel) with a cord on the object without moving or tilting it;
- if possible, the most important sectors of space, in which the scattering of fragments and the propagation of a direct shock wave is unacceptable for one reason or another (people, utility lines, material assets), must be shielded with the simplest homemade protective structures based on sand or water. The use of special anti-bomb (anti-fragmentation) mats or blankets placed directly on a suspicious object is highly undesirable due to the risk of triggering a fuse with an unextractable element;
- Hide behind cover and make sure that there are no other people in the immediate area, pull the cord, trying to tip (tilt) the object or at least move it.
If no explosion occurs, then the probability of the presence of a fuse with a non-removable element in the suspicious object is negligible, although the explosive device itself may be present.
When opening or checking the contents of a bag, package, or parcel (if this is provided for by the job description), special attention must be paid to the thin threads between the sliding parts of the object, which may be the threads of a tension detonator or a hand grenade fuse. Naturally, further opening must be stopped, especially since applying additional force to open is unacceptable. In extreme cases, opening must be done remotely from behind cover using cords.
A very effective method of destroying suspicious objects without approaching them is by shooting them with a firearm. However, in this case, when destroying a real explosive device, there is a serious risk of a conflict with the investigative bodies, since such actions can be classified as intentional destruction of material evidence of a crime.
Among the special technical means that can significantly simplify the solution of the problem of detecting explosive objects and identifying them, we can note X-ray equipment (portable and stationary versions), detectors of time and electronic fuses, non-linear radars (enabling the detection of electronic components) and metal detectors of various types.
Unfortunately, the problem of combating explosive terrorism is not limited to the scope of this article, which only considers certain aspects. Naturally, each specific case will require the creation of appropriate job descriptions, detailed development of recommendations on the procedure for the actions of officials and their appropriate training. The author of the article will be grateful for critical comments, recommendations and suggestions in light of the solution to this problem.