with the shallowest being dug out first since they have the greatest chance of survival. probing can be a very time-consuming process if a thorough search is undertaken for a victim without a beacon. in the u.s., 86% of the 140 victims found (since 1950) by probing were already dead. survival/rescue more than 2 m deep is rare (about 4%). probes should be used immediately after a visual search for surface clues, in coordination with the beacon search. shovels even when the snowpack consists of loose powder, avalanche debris is hard and dense. the energy of the avalanche causes the snow to melt, and the debris refreezes immediately after it stops. shovels are essential for digging through the snow to the victim, as the snow is often too dense to dig with hands or skis. a large strong scoop and sturdy handle are important. plastic shovels often break, whereas metal ones are less prone to failure. as excavation of the avalanche victim is extremely time-consuming and many buried victims suffocate before they can be reached, shovelling technique is an essential element of rescue. shovels are also useful for digging snow pits as part of evaluating the snowpack for hidden hazards, such as weak layers supporting large loads. recco rescue system the recco system is used by organised rescue services around the world. the recco system is a two-part system where the rescue team uses a small hand-held detector. the detector receives a directional signal that is reflected back from a small, passive, transponder called a reflector that is included into outerwear, boots, helmets, and body protection. recco reflectors are not a substitute for avalanche beacons. the recco signal does not interfere with beacons. in fact, the current recco detector also has an avalanche beacon receiver (457 khz) so one rescuer can search for a recco signal and a beacon signal at the same time. avalung recently, a device called an avalung has been introduced for use in avalanche terrain. the device consists of a mouth piece, a flap valve, an exhaust pipe, and an air collector. several models of avalung either mount on one's chest or integrate in a proprietary backpack. during an avalanche burial, victims not killed by trauma usually suffer from asphyxiation as the snow around them melts from the heat of the victim's breath and then refreezes, disallowing oxygen flow to the victim and allowing toxic levels of co2 to accumulate. the avalung ameliorates this situation by drawing breath over a large surface area in front and pushing the warm exhaled carbon dioxide behind. this buys additional time for rescuers to dig the victim out. avalanche airbags avalanche airbag system with visible airbags avalanche airbags help a person avoid burial by making the user an even larger object relative to the moving snow, which forces the person toward the surface. avalanche airbags work on the principle of inverse segregation (granular convection). avalanches, like mixed nuts and breakfast cereal are considered granular materials and behave fluid-like (but are not liquids) where smaller particles settle to the bottom of the flow and larger particles rise to the top. provided the airbag is properly deployed, the chances of a complete burial are significantly reduced. with freeriding becoming more popular in recent years, avalanche airbags have become (relatively) commonly used equipment, with one german producer reporting over 20,000 sales in the 2012/13 winter season. one complication is that the small explosives or compressed air canisters that deploy the airbag might need to be emptied or expended in order to fly on a commercial airplane. though the international air transport association has approved carrying charged devices, the u.s. transportation security administration requires that they be discharged. for this reason, some users who travel by air buy a new canister or refill an empty one after arrival. in 2014, one company introduced an airbag system that uses a battery-powered fan to inflate its 200-litre (7.1 cu ft) bag in around 3.5 seconds. avoiding the use of compressed gas is claimed to avoid problems with travel restrictions. the manufacturer claims a number of other advantages for the system, such as the ability to easily and repeatedly test it, the ability of a continuously operating fan to keep the airbag inflated even if it receives a puncture or small tear and the fact that the bag can be easily deflated and repacked, making the system available for a second deployment if needed. other devices more backcountry adventurers are also carrying satellite electronic notification devices (send) to quickly alert rescuers to a problem. these devices include the spot messenger, emergency position-indicating radio beacon (epirb) or personal locating beacons (plbs) containing the global positioning system (gps). this device can quickly notify search and rescue of an emergency and the general location (within 100 yards), but only if the person with the epirb has survived the avalanche and can activate the device. survivors should also try to use a mobile phone to notify emergency personnel. unlike the other devices mentioned above, the mobile phone (or satellite phone) provides two-way communications with rescuers. on-site rescuers (usually companions) are in the best position to save a buried victim. however, organized rescue teams can sometimes respond very quickly to assist in the search for a buried victim. the sooner organized rescue can be notified the sooner they can respond, and this difference can mean the difference in living or dying for a critically injured patient. the international commission for alpine rescue recommends, “early notification is essential, e.g., by mobile phone, satellite phone, or radio, wherever possible” other rescue devices are proposed, developed and used, such as avalanche balls, vests and airbags, based on statistics indicating that decreasing the depth of burial increases the chances of survival. although inefficient, some rescue equipment can be improvised by unprepared parties: ski poles can become short probes, skis or snowboards can be used as shovels. a first aid kit and equipment is useful for assisting survivors who may have cuts, broken bones, or other injuries, in addition to hypothermia. types of rescue self-rescue is the process where victims caught in an avalanche escape by either digging themselves out, or after the snow melts. self-rescue is rare as the victim is usually "entombed" by the snow and unable to move at all. however, if the avalanche is small, or the victim is buried near the surface, or the avalanche debris is soft, victims may be able to dig themselves out. when attempting to dig themselves out, victims usually find it difficult to gauge which way is up. a common myth is that spitting while covered in snow can help a victim determine the direction upwards. spitting while covered in snow does not help because when the snow has settled, it becomes solid and movement is mostly not possible. in some cases, the snow may begin to melt, and the victim may be released from the snow after it thaws. companion rescue is when victims are rescued by other members of their group. when professional and volunteer rescue teams become involved, the process is referred to as organized rescue. in case of organized rescue, the first teams travel fast and light to locate and uncover buried victims. these teams carry basic rescue equipment, including rescue dogs and recco detectors, and emergency-care gear. these rescuers are generally not equipped for prolonged operations. avalanche in karaj county upon the first alert of an avalanche incident the rescue leader will appoint a team to arrange transportation for both rescuers and patients. rescue leaders will assess the complexity of the search and rescue operation to determine and anticipate the needs for support. every incident is different depending upon the number of victims, avalanche danger, weather conditions, terrain, access, availability of rescuers, etc. support includes getting appropriate resources of people and equipment, transporting the resources, caring for and replacing rescuers. in the united states all agencies are mandated to manage search and rescue operations, including avalanche, under the incident command system (ics).