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Bloons Wiki
Sprays foam that removes camo and regen, and pops leads.
~ BTDB Steam description

Cleansing Foam is the third upgrade on Path 1 for the Monkey Engineer in BTD5. It allows the engineer to shoot blobs of foam onto the track that remove Camo and Regen properties of bloons, as well as pop Lead Bloons on contact. Without attack speed bonuses, the engineer can have up to 3 blobs on the track at once. These dissipate after 8.2 seconds or (on mobile versions) 30 bloons pass by, whichever happens first.

It costs $680 on Easy, $800 on Medium, $865 on Hard, and $960 on Impoppable.


  • Place a 3-x Cleansing Foam as far from the track as possible, so as to minimize the random distribution of the foam globs.
  • The Cleansing Foam is incapable of directly popping non-lead bloons, although there is a bug where it can damage any bloon type on mobile versions if the engineer is given lead-popping power.
  • This upgrade removes the camo property from D.D.Ts.
  • In the Flash version of BMC, the blobs of foam have infinite piece and thus have no hard limit to the amount of bloons they can cleanse. This makes the upgrade super powerful, effectively removing all bloon effects if placed at the start of the track.

Differences Between BTD5 Flash and BTD5 Mobile[]

NERF Cleansing Foam costs more ($750 → $800) and no longer has unlimited pierce(BMC-exclusive).

Update History (Bloons TD Battles Mobile)[]


BUFF Cleansing Foam price decreased ($800 → $650).


  • The Monkey Engineer doesn't aim the foam with his gun, so the globs of foam can come from the side or back of the Monkey Engineer.
  • There is a glitch in BTD5 mobile where the Monkey Intelligence Bureau allows the cleansing foam to pop any type of bloon and damage MOAB-class bloons in a manner similar to Road Spikes. This is likely due to the foam being able to pop Lead Bloons. The same may happen if the Engineers Workshop specialty building is active.
  • This upgrade gives the Engineer a blue tank on their back that resembles a Glue Gunners with tier 1 upgrades.