Shuriken Explosion Example - Collision

Hi,

I was playing around with the explosion example that was in the Shuriken Examples project, and I was trying to prevent the explosion (fireball etc) from going through an object (i.e a wall) so it doesn't appear through the other side to the player, however I just can't figure it out.

Here are the examples.

http://beta.unity3d.com/3.5-preview/ShurikenExamples.zip

I also played around with the Detonator framework, and couldn't work out how to do it.

http://unity3d.com/support/resources/unity-extensions/explosion-framework

Any advice?

Thanks