Lesson 8: Probing

Proper Probing Technique

Effective probing is critical for effective and fast recovery. When probing, the following techniques should be followed:

  • Be systematic and thorough.
  • Use two hands with gloves on.
  • Start probing by probing between your feet.
  • Leave the probe in place when you suspect a strike.
  • If unsure of a strike, leave the probe in place and continue with another probe.
  • If approximate depth is known, probe only 30% deeper than this.

Probing Methods

Professional responders must be familiar with and practice all probing methods. Different methods may be used depending on the stage of the response and whether or not the subject is wearing a functioning transceiver.

Spot Probing. Performed in likely burial areas (trees, rocks, and depressions) when transceiver searching is not an option.

Grid Probing. Performed after a successful transceiver search.

  1. Stand one-step back from where the strongest transceiver signal was found.
  2. Probe Centre, Left, Right.
  3. Probe Front-centre, Front-left, Front-right, Back-centre, Back-left, Back-right. This completes the first square.
  4. Take a step back. Begin probing clockwise around the first square to complete the second square. Count 1, 2, 3, 4 around each side starting below Back-Right of the first strike.
  5. If two squares yield no strikes, return to the centre, rotate 45 degrees and repeat the grid.
  • Probe in front of you. It is easier than probing between your feet
  • Probe perpendicular to the slope angle. The transceiver signal travels to the shortest distance, which is 90-degrees to the surface.
  • Use probe spacings of 20-25cm.
  • Do not revert back to a fine search. Continue to probe until a probe strike is made.
  • Leave the probe in the snow to mark the subject’s precise location.
  • Avoid stepping on the top of the subject (especially in the case of shallow burials).

Position Probing. Performed after a probe strike is made. Knowledge of the subject’s position is desired to facilitate shovelling and to more efficiently access the subject’s airway. This operation must be done quickly because time is of the essence.

  1. Leave the probe in the snow to mark the strike.
  2. Continue using the spiral method with additional probes to establish the person’s orientation and detailed position.

Three-Holes-Per-Step Probing. 3HPS is an organized probing method to search for subjects who do not have functioning transceivers. It may also be used in conjunction with other search methods if the avalanche area is large enough and there are enough rescuers on the scene. Leadership is crucial in organized probing. The line leader may be separate from the line, or if required to participate in the search, should be positioned in the centre where their voice will be clearly heard by everyone.

  1. The search should be conducted moving uphill, unless the terrain is very flat.
  2. Searchers should stand fingertip to fingertip for the initial coarse search.
  3. Each searcher probes on command; (Centre, Left, Right, Forward), maintaining a 50cm grid spacing.
  4. Searchers then step forward 50cm and repeat the procedure.
  5. The use of guide cord is recommended to facilitate precise probe placement.

If two complete passes of the search area are unsuccessful, then probers should realign shoulder to shoulder (25cm grid spacing) and continue probing in a fine search. The fine search requires a probe master and strict marking to ensure optimal coverage. If the fine search is unsuccessful, a grooming machine may be used to gently remove the top 1m of snow.

Slalom Probing. Slalom proving is another organized probe-line technique used to search for subjects without functioning transceivers. This method requires that each rescuer be responsible for searching a 1m-wide strip of the avalanche debris. Probing is done walking in a “slalom” pattern across the strip. Studies show an increase of up to 50% in the speed of this method compared to the 3HPS method.

  1. Searchers stand fingertip to fingertip for the initial coarse search.
  2. The searcher always probes directly in front of his or her body, perpendicular to the surface.
  3. Commands are given by the probe-line leader; (Probe, Right, Right, Forward, Left Left, Forward), maintaining 50cm grid spacing.
  4. Probing depth should be limited to 1.5m on the first pass.
  5. If as second pass is required, searchers should adjust positions slightly to the left or right in the probe line (offset) and probe 2.5m deep. Adjusting the position of probers allows for randomized probe hole spacing
  6. After two passes, searchers should realign shoulder to shoulder and continue with a fine search

Standardized Flagging

The International Commission for Alpine Rescue (ICAR) has adopted standardized flagging to help reduce the potential for errors by ensuring consistency between different search groups. Flagging also helps to ensure an efficient rescue by maintaining a clearly laid out and organized scene.