Intangibles in the TADS 3 library constitute things that have some kind of presence but are not physical objects, such a light, smoke, smells and sounds. The class hierarchy for Intangible is:
Intangible
DistanceConnector
SensoryEmanation
Noise
SimpleNoise
Odor
SimpleOdor
Vaporous
SenseConnector
DistanceConnector
While we're looking at intangibles and sensory things, we'll also cover:
SensoryEvent
SoundEvent
SoundObserver