You want to tell Particular to emit from a layer — in your case your masked lock that has been precomped:
This is from the help manual that you can find by going into particular effects window/ click on “options” then click on “help” at the bottom of the options window:
In Particular, set Emitter>Layer to your precomped “lock” layer. Notice that a new light named “LayerEmit [layername]” is created. This is a control light that Particular uses to keep track of the layer. It is locked and shy and it’s not supposed to be edited.
Set Emitter>Emitter Size Z to 0 (zero).
Try a RAM preview to see particles emitted from the text. Notice that all particles are behind the layer. To fix this, move the Boom layer to the bottom of the TLW. Then set in Particular Visibility>Also Obscure with to “Layer Emitter”.
Jim Dodson
8 Core Intel — Mac – OSX