I would generally rule that finding a proximity trigger without triggering it takes twice as long as just searching a square normally. Also, that it can only be done by one person at a time, slowing down the process even more.
Since these are triggered by vibration, be aware of talking loudly or other action the party might take to set it off.
Another way to handle these triggers is to just set them off. Throw a thunderstone down the hallway and cover your ears.
The biggest clues you have in order to detect a trigger of this type are the signs that the area has not been disturbed or visited in a long time. Examples above, such as dust, are useful; other signs of proximity triggers in use include:
- Cobwebs
- Sagging shelves and furniture or curtains
- Hard stone or metal hallway floors or acoustical ceilings to increase the noise made
- The section of the dungeon is a sealed or is clearly a vault.
Traditional use
C2: Ghost Tower of Inverness by Allen Hammack
6. BUGBEAR ROOM. . .
This 90'x90' room has a 20' high ceiling; there is a 10' wide passage in the center of the west wall. In the room are 16 bugbears without weapons, standing perfectly still; however, they do not appear to be statues. In the center of the north wall is a 10' long, 5' wide, 5' tall stone sarcophagus engraved with lettering.
The bugbears are in a type of temporal stasis; 4 will animate. . . and attack any intruders within the room each time one of the doorways is passed through. (For example, if a party member steps into the room and then out again, 8 bugbears will be animated.) The doorway, and not the floor, is the trigger: flying and levitation spells will still animate the monsters, characters using dimension door and teleport spells will not activate the bugbears, regardless of whether the room is entered or passed thereby.
T1-4: Temple of Elemental Evil by Gary Gygax
210. OCTAGONAL CHAMBER
If the bronze doors in area 145 (Dungeon Level One) are sundered, the stairs therein descend south to this room. However, entry is blocked by another set of like doors, set in the north wall of this area.
Illumination in this large octagonal room seems to come from everywhere — ceiling, walls, floor — a milky radiance which gives a dim and eerie glow to the whole scene. The floor of this place is 15' below the level of the normal dungeon floor, with short broad stairways leading to it. The ceiling vaults to a height of 40 feet. The walls and floor of the room are of polished gray stone with whorls of glittering mica; the floor is partially obscured by swirling, eddying, softly glowing mist. In the center of the area is a great pierced square of bronze, ten feet on a side. A dome is pierced in the northern ceiling, a circular shaft some 20 feet wide opening directly over a pit of the same diameter and five feet depth. Immediately to the south of the pit is a block of alabaster two feet wide, four feet high, and eight feet long. Atop it are two knives and a bowl of finest crystal. Ranking the pit are two crystal braziers, suspended from tripods by chains of silver. Each emits a faint sickly-sweet perfumed smoke. The doors to the north are bronze, sealed with iron, chained, barred, and bear a warning inscription in runes of some sort.
The altar stone and crystal service pieces are protected by a special glyph of warding suitable to the place. They cannot be safely touched unless the symbol of the Air Temple is worn and the glyph name, whah-duh, is spoken. Failure in either requirement causes a whirlwind to suddenly form and spin from the pit to the altar, inflicting 12 points of damage to each creature within ten feet of its path (save vs. spells to take half damage). This also triggers an alarm; the whole area gives off an evil-sounding chiming and tinkling, and the guardian is summoned.
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