Test Probe 18: Checking an Enclosure the Way a Child Would

Most accessibility testing imagines an adult hand. IEC 61032 Test Probe 18 exists for the other case: a small, jointed finger that reaches into gaps an adult hand ignores. Household appliance safety standards, notably IEC 60335-1, require it alongside the standard test finger, because the two probes disagree on exactly the openings where children get hurt, small vents and control-panel gaps.

How it differs from the adult finger

Probe 18 is slimmer than the 12 mm adult test finger and has a more flexible joint, which lets it curl into recesses and reach past obstructions at odd angles. It carries a stop face sized for the standard test forces. The point is not that children are stronger than adults; it is that their fingers are smaller, so a slot that blocks the adult probe can admit the child probe, and the standard treats that as a failure even though no adult hand would ever fit.

Where the two probes disagree

The disagreements cluster in predictable places. Ventilation slots narrower than 12 mm but wider than the child probe pass the adult check and fail the child check. Control-panel gaps around switches and knobs behave the same way. Standards handle this by requiring both probes, or by requiring the child probe with a reduced force, so read the specific product standard rather than assuming one verdict covers both.

Opening type	Adult probe B	Child probe 18
Vent slots, 4-8 mm	Blocked, passes	May admit, fails
Knob gaps around 6-10 mm	Blocked, passes	May admit, fails
Wide openings over 12 mm	Both probes enter; judged on hazard separation

Bench practice

Run the adult finger first, then the child probe, and note each opening by position rather than by a single pass/fail line. Photograph any opening where the child probe enters but touches no live part, since these borderline photos are what turn a disputed report into a discussion instead of a rejection. Store Probe 18 in the same case as Probe B so the pair never gets separated on a busy bench.