5.1 Tools and Probes to Identify Entrapment

Tools and probes to identify entrapment

Domain 1K of the National Recreation and Park Association (NRPA) Certified Playground Safety Inspector (CPSI) blueprint tests whether you can prove a head- or neck-entrapment finding with the tools in American Society for Testing and Materials (ASTM) F1487-21 Standard Consumer Safety Performance Specification for Playground Equipment for Public Use and U.S. Consumer Product Safety Commission (CPSC) Public Playground Safety Handbook, Publication 325 (July 2025), Appendix B. Domain 1J named the cause — an opening that admits a torso and holds a head, or a V- or U-shaped angle that admits a neck and holds the head. This section is the method. A narrative that says “the ladder looks tight” without a named probe, an orientation, and a pass/fail is not an inspection finding.

The dimensional crib sheet in the exam room is the NRPA Table of Dimensions, Rev 1/2024. Do not invent a fourth probe, do not reverse torso and head, and do not substitute a tape-only “between 3.5 and 9 inches” shortcut for the fixtures. CPSC §3.3.1 still tells you that openings whose interior opposing surfaces sit greater than 3.5 inches and less than 9 inches are the suspect range, and that all dimensions of that opening must be considered together. The probes exist because a 4-inch-wide by 10-inch-tall slot and a 4-inch circle are not the same opening.

Completely bounded openings: torso probe first, then the head probe

A completely bounded opening is a hole whose perimeter is closed on all sides — a ladder rung gap, a barrier slat space, a climber diamond, a steering-wheel spoke, a roof opening — and that is not bounded on the bottom by the ground. CPSC Appendix B.2.4 / B.2.5.3 and F1487 treat every such opening, even one low enough that a child’s feet can touch the surfacing, as a potential head-entrapment hazard. Younger children may not have the motor skill or the composure to reverse a stuck head.

The official sequence is the one in CPSC Appendix B.2.5.3 and the matching F1487 torso/head performance test. Do not invent another order.

1. Select the preschool/school-age torso probe used on F1487 public-use equipment: 3.5 in thick × 6.2 in wide (NRPA Table, Figure A1.2). CPSC calls this the small torso template. Its job is to represent the smallest user at risk who can still get a torso through feet-first.
2. Identify every completely bounded opening on accessible equipment, including moving equipment tested in its stationary position.
3. Offer the torso probe with its plane parallel to the plane of the opening. Rotate it to the most adverse orientation — major axis of the probe parallel to the major axis of the opening — while keeping that plane parallel.
4. Ask whether the torso probe can pass freely. If it cannot, stop and pass. The opening is too small for a torso, so it is generally not a head-entrapment opening. A child’s head is larger than that torso; an opening that will not admit the small torso will not admit a head-first entry either.
5. If the torso probe does pass, immediately apply the 9-inch head probe (NRPA Table, Figure A1.3; CPSC large head template) with its plane parallel to the opening. The head probe must also pass freely. If it does, the opening is large enough for the largest user at risk to withdraw a head in any orientation — pass. If the opening admits the torso and holds the 9-inch head, fail: that is the classic feet-first head-entrapment hazard.

Two special completely bounded cases sit in CPSC Appendix B.2.5.4 and B.2.5.5. Limited-depth openings — a step-ladder against a barrier is the handbook example — have two planes: Plane A is the opening you first see, Plane B is the horizontal space behind the lower boundary. Test both planes with torso then head. A child can go feet-first through the rung gap and then have the head caught in the space between the step and the barrier. Flexible openings (cargo nets, climbing membranes) change shape under load. CPSC Appendix B.2.5.5 applies the three-dimensional torso and head probes with a force of 50 pounds on preschool- and school-age playgrounds (30 pounds on toddler playgrounds under ASTM F2373). The number the CPSI exam table prints for F1487 public-use equipment is 50 lbf applied to the head or torso probes (NRPA Table, F1487 6.1.2.1). Use that 50 lbf figure on 2-through-12 public-use nets unless you are inspecting a separate F2373 toddler setting.

Partially bounded openings: the neck / A / B probe

A partially bounded opening is a U- or V-shaped angle that is open on at least one side — the junction of a slide hood and a guardrail, the crotch of a climber, two adjacent pipes, a roof peak. CPSC §3.3.2 adds a geometry screen: angles formed by two accessible adjacent parts should be greater than 55 degrees unless the lowest leg is horizontal or below horizontal. That 55-degree note does not replace the probe. Use the partially bound opening test in Appendix B.2.5.6 on every accessible angle that meets the handbook’s “identify” rules (perimeter not closed; for preschool/school-age, the lowest leg tilted upward).

The preschool/school-age template (CPSC Figure B9; NRPA Table 6.1.4) is one fixture with three published dimensions you must be able to name:

• Neck: 3 in long × 1.875 in wide — the part that represents a child’s neck entering the crotch of the angle.
• Probe A: 6.1 in width — the triangular “head-first” section you offer first, narrow tip toward the opening.
• Probe B: shoulder width 8.5 in, thickness 0.75 in — the shoulder/neck section you offer after A if the opening is still in play.

CPSC Appendix B.2.5.6.1 is the sequence. Align the face of the template parallel to the plane of the opening with the narrow tip of section A pointing toward the opening. Insert A along the centerline. If both top corners at the narrow tip of A make simultaneous contact with the sides of the opening, pass and stop — the angle is too tight for a neck to bottom out. If A goes farther, check whether both angled sides of A also contact the opening; if the tip simply rests on the lower boundary with no side contact, pass. Otherwise rotate the template so its face is perpendicular to the opening and insert the B (neck/shoulder) portion. For preschool/school-age equipment, if B passes the A contact points and the opening does not enlarge enough for the 9-inch head probe to pass freely, fail. Do not skip from a tape measurement of “about 50 degrees” to a fail without running A then B.

Where to test, and what to write down

Test all completely bounded openings in the entrapment range and all accessible partially bounded angles. That includes barriers, guardrails, ladders, climbers, roofs, steering wheels, track-ride frames, and openings on moving equipment (tested at rest, then re-checked if motion changes the opening). An opening whose smallest interior dimension is clearly under 3.5 in still gets the torso probe if you cannot prove the size without the fixture. An opening larger than 9 in in every orientation is outside the head-entrapment window, but a diamond that is 10 in on the long axis and 4 in on the short axis is still in range until the probes say otherwise.

Document, at minimum, the equipment identifier and age group; the exact opening (for example, “north barrier, third slat from the west post, 18 in above the deck”); which probe you used and the orientation; pass or fail; the cited criterion (F1487 6.1 / CPSC Appendix B.2.5 / §3.3); and the priority. A torso-pass / head-fail opening is a Priority 1 head-entrapment finding. The owner still decides repair versus removal. Your job in Domain 1K is to leave a third party able to re-find the same opening and repeat the same sequence.