Clarifications on Passive Senses
( ⇪ House Rules )
(Inferred from Rules Compendium page 9)
You can assume that everyone is constantly taking 10 on Spot and Listen checks. This represents a creature’s ability to passively spot something in their peripheral vision provided that it isn’t camouflaged (which provides concealment) or obscured (which provides an improved cover bonus to a Hide check) or passively hear something provided that it isn’t quiet (like whispering) or muffled (such as through a door or wall).
For every 10 ft of distance between you and the creature or sound, the Spot or Listen DC increases by 1. This means that a creature will automatically spot or hear something until taking 10 would result in a Spot or Listen check too low to hear it (once they see it, they know where it is until it’s out of line-of-sight). Spotting a medium-sized object adjacent to you is a DC 0 Spot check, and hearing someone talk adjacent to you at a normal speaking volume is a DC 0 Listen check. To hear someone that’s whispering, unless you have a good enough listen modifier you’ll have to step into their square to hear it passively.
A basic human skeleton warrior has a WIS of 10 (WISmod +0) and no ranks in Spot or Listen. This means that when it takes 10 on a Spot or Listen check, it gets a 10. Let’s assume that it’s walking along and a medium-sized TV is speaking nearby. It will automatically see the TV or hear it when the TV is less than 100 ft away because for every 10 ft of distance the DC for both checks increases by 1.
It can be generally assumed that most of the time most people are distracted by what they are attempting to accomplish at that moment. If this is not the case (such as when you’re explicitly “on watch”), then the results of your check are as in the example above. If the human skeleton were distracted, however (such as by a battle), the Spot and Listen DCs increase by 5, so his effective passive peripheral vision and passive hearing each decrease by 50 ft.
For the purposes of a Spot check, objects of that size take up roughly the same amount of space as a creature of that size. Use the object’s longest visible length to determine its size For example, a 5ft × 5ft × 5ft block of stone is “medium”-sized, as is a 6ft × 3ft × 2ft crate. Objects are considered to be constantly hiding but have an effective roll of 0, and a Hide modifier of +0 not counting for the size modifier.
The Hide check modifiers for size are as follows:
- Fine +16
- Diminutive +12
- Tiny +8
- Small +4
- Medium +0
- Large -4
- Huge -8
- Gargantuan -12
- Colossal -16
- Planetary -20
- Astronomical -24