(The rescue information on these pages is quite detailed. If you are short on time or looking for a quick review, you can jump to the Avalanche Rescue Summary.)
Compared to using a digital avalanche transceiver, finding a buried person by pushing a stick into the snow is caveman-style searching. However, probing is reliable. Yes, you may mistakenly think you hit the victim when you haven't (a false positive), but your probe will never pass through the victim (a false negative).
A probe that hits a human body, or a backpack, has a slightly springy, "boingy" feel. Don't press too hard. Your job is to locate rather than perforate. Branches can also have a springy feel (and occasionally I've smelled the scent of pine on the tip of the probe). A probe that hits skis, a boot, or a snowmobile has a much different feel. As you would expect, rocks have a hard feel and can make a clicking sound. Ice layers (and sometimes frozen dirt) can have a "sticky" feel where the tip of the probe is momentarily held by the ice. If you are unsure whether your probe is contacting the victim, probe several times around your initial probe hole to gauge the size and "feel" of the object.
When you find the victim with your probe, leave it in place and begin shoveling. It is important that you leave your probe in place so you dig in the correct location. The probe is also a good reminder to not stand on top of the victim.
When purchasing an avalanche probe, consider only a dedicated sectional probe. Convertible ski pole probes might be okay as a backup, but they are too short, too difficult to assemble, and they are lousy at penetrating dense avalanche debris.
Your dedicated probe should have an assembled length of at least 220 cm. Short probes require that you bend over each time you insert the probe; Long probes are necessary only when probing an unsurvivable deep burial and are more appropriate for patrollers and search and rescue teams. Generally speaking, I suggest 280 cm probes for backcountry travellers and 320 cm probes for patrollers and professional rescuers. Etched depth indicators and contrasting segment colors are helpful for determining burial depth and measuring snow pits.
Look for a simple assembly mechanism that locks, by pulling on a handle or cable, and that does not require any fiddling to lock it. Don't use probes that require you to position a knot in a tiny groove or that require you to manually spin a knurled nut, and don't buy any probe where the tubes can accidentally come off the cable/string. Make sure you can reliably deploy the probe with your typical winter handwear (e.g., mittens). And practice deploying your probes frequently.
The Pieps iProbe is a unique probe that can temporarily silence a Pieps transmitter.
Transceiver probing takes place after completing a transceiver fine search. It is an important step to confirm that you are in the correct location before you begin digging.
After completing the fine search, you should stow your transceiver so it doesn't interfere with probing and shoveling. And after you start probing, trust your probe and avoid the temptation to return to your transceiver. The time you "waste" probing a larger area is usually small compared to the time you will waste returning to a transceiver search.
Hold the probe firmly with both hands (don't cling to your transceiver with one hand—it should be stowed). When probing for a transceiver signal, insert the probe at 90° relative to the snow rather than relative to gravity. This is because your transceiver will take you to the closest location relative to the transmitting beacon, which is not necessarily directly above the victim. If you mistakenly hold your probe vertically (a common mistake), the transmitter will be uphill of your first probe. (When spot probing, the probe can be held at any angle; when used in a probe line, the probe should be held vertically to gravity.)
You should first insert your probe at the location where your avalanche transceiver reported the strongest signal (i.e., the shortest distance). Subsequent probes should be in circles (or a spiral as proposed by Manuel Genswein in 2002) from this center point at no more than 25 cm (10 inch) intervals. This small distance between holes ensures that you will not miss the victim. It is better to "waste" a little time probing tightly than to miss and have to re-probe the entire area.
If your fine search was decent, you should find the victim within the first or second circle (i.e., a 20 inch radius). Even if you encountered a spike (which is very uncommon with modern, three-antenna transceivers) or your fine search was sloppy, continuing to probe every 25 cm (10 inches) will eventually locate your victim. (My rough time estimate is that probing a one-meter radius [which would be a huge miss] at 10-inch intervals will take less than five minutes.)
When you find the victim with your probe, leave it in place and begin shoveling. Leaving the probe in place will help you stay on-target as you shovel and will remind you to not stand on the victim which might compromise his airway.
Spot probing involves probing high-probability areas. It is used when the victim doesn't have an avalanche transceiver or when the transceiver has stopped transmitting.
High-probability areas include probing downhill of clues (e.g., skis or a snowmobile), uphill of catchments (e.g., trees, bushes, rocks), in depressions, near the toe of the avalanche, downhill of the point last seen, etc.
During spot probing, it is advisable to not probe deeper than 2 meters (6 feet). Surviving a such a deep burial is extremely unlikely; it is a better use of your time to search more locations.
You can hold your probe at any angle when spot probing (when probing after a transceiver fine search, the probe should be held at 90-degrees relative to the snow surface).
A probe line search is appropriate when the victim cannot be located using a transceiver or by other readily available means (e.g., RECCO, spot probing, dogs, etc). A probe line requires a large number of rescuers and is a slow process. It is usually considered a recovery, rather than a rescue, technique. Probe lines are typically instigated by professional rescuers (e.g., ski patrols or SAR teams) and are rarely used during companion rescues.
A probe line involves a row of rescuers repeatedly inserting avalanche probes into the snow and then advancing. It is an effective albeit slow way to search an avalanche.
A probe line typically has a leader, probers, and possibly two people who manage a guidon cord. The probers can be bystanders who are trained on the spot.
The following slideshow illustrates the probe line process (click on the right-arrow to advance through the slides). These instructions assume 50 cm (20 inches) between probe holes. This coarse spacing has about an 80% chance of finding a person on the first pass. It's a good balance between speed and thoroughness.
When used in a probe line, the probes should be held vertically relative to gravity (i.e., plumb). When probing after a transceiver fine search, the probe should be held at 90-degrees relative to the snow surface.
Probers. It is much easier on the probers' backs if they face uphill. This also gives them better situational awareness—not that they could outrun an avalanche. The probers can achieve the desired five-foot spacing by standing palm-to-palm.
Lines People. The optional lines people can hold a guidon (pronounced "guide-on") cord that is typically marked (either with paint, knots, or ribbon) every 50 cm (20 inches). The markings help keep the probers in a line and ensure proper spacing between probe holes, but the spacing will be good even without a cord provided the probers maintain the five-foot spacing.
The most important task performed by the lines people (and this can be done by the probers on the ends of the probe line) is to periodically place flags adjacent to the outside probe hole. Knowing the terrain that has been probed is critical as the incident commander adapts the search plan.
Leader. The leader is ultimately responsible for the entire probe line search. In addition to giving the verbal probing commands, the leader must ensure that proper spacing is maintained between probers and that the probers remain focused. The leader can observe the heights of the inserted probes to gauge the underlying terrain versus a possible probe spike. Additionally, the leader may need to train bystanders so they can participate in the probe line.