Explosion triggering another explosion

I have an explosion which is basically a particle system. I want this explosion, when contacting some objects, to trigger another explosion. Kind of a chain reaction of explosions.
So I added colliders both to the explosion and the object and marked the “Is Trigger” option.
Next I attached a script to the object and hooked the OnCollisionStay method.

For some reason this does not work. The collision is no detected.

My guess that this is because the both explosion and object are not moving and the explosion just appears near the object, so entering a collision is not detected. But I don’t know how to solve this problem.

OnTriggerEnter and OnCollisionEnter (and Stay and Exit) have specific requirements upon the objects (see table at bottom of Collider doc pages), which you are not meeting, most likely neither is a Rigidbody. I’d actually suggest you implement it “manually” by checking for objects inside the explosion using OverlapSphere or some such, rather than abusing physics for the purpose, because you’ll also have to prevent unwanted side effects, and it will be inefficient anyway.