Humidity

Caves are warm and damp places. 

They have condensation and water droplets which accumulate on their ceilings.

Save the image below to use for a new 

Particle Object called CaveHumidy

Add a CaveHumidity Particle to the top of the scene near the middle

Set the size and angle of the CaveHumidity particle as shown

Change the particle properties to those shown below

Change the initial properties as shown

Change the lifetime properties as shown

Run your scene. You should see drops falling randomly from the cave ceiling now.