These explosions can be activated by a Switch or Touchplate.

Place as many SEENINE/OOZFILTER explosives tagged [Channel,DelayExplosion] as you want. For DelayExplosion, a value of 30 = 1 second. If you want to make the explosives intangible in the game, shrink them horizontally (x-wise) as much as possible. Raise each one to the height at which you want it to explode. Each SEENINE/OOZFILTER must have a Lo-Tag value or else it won't visibly or audibly explode (although it will still shake the screen and spawn debris). It is also recommended to assign time-delay Lo-Tag values to linked tangible explosives, because in the case of multiple tangible explosives, only the one with the largest sprite number will visibly and audibly explode. Place a D[0,Channel] in just one sector containing a SEENINE/OOZFILTER explosive (the Channel will link the rest of the explosives together). Place either a T[0,Channel] or else a Switch tagged [ActivationSound,Channel] somewhere in the map (to trigger the explosion).

Note: You can link a SEENINE/OOZFILTER explosive tagged [Channel,DelayExplosion] to an S[Channel,13]. When you activate the trigger, the SEENINE/OOZFILTER (tangible or intangible) will also activate the S[Channel,13].