Cleansing Foam is the third upgrade on the first path for the Monkey Engineer in BTD5. It allows the Monkey Engineer to shoot a blob of foam that can remove Regen and Camo properties of bloons, as well as pop Lead Bloons. Up to 3 blobs of foam are able to be applied onto the track at once, unless the Monkey Engineer has an attack speed boost which will add more blobs on the same map. If a certain amount of bloons go over the foam, it disappears, regardless of if they are Camo, Regen, or Lead.

Cleansing Foam makes a return as the third upgrade on the second path for the Engineer Monkey in BTD6. Blobs of foam will regularly land on nearby track every 2.0s, independent of the main attacks. These blobs can remove Camo or Regrow properties or damage Lead properties. Each blob of foam lasts 8.5 seconds on the map before disappearing or after 10 bloons pass by the blob, whichever comes first. It costs $800 on Medium. Cleansing Foam will take the camo off of DDT's, making this one of the cheapest ways to allow towers to attack DDT's.

Verion history (BTD6)Edit


Buff 2-3-0 Cleansing Foam now has increased attack speed (2.0s --> 1.2s)

Buff 0-3-1 Cleansing Foam now has more pierce (10 --> 15)

Differences Between BTD5 Flash and BTD5 MobileEdit

Nerf Cleansing Foam costs more ($750 → $800) and no longer has unlimited pierce.

Update History (Bloons TD Battles Mobile)Edit


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.
  • This upgrade gives the Engineer a tank that resembles a Glue Gunner with Glue Soak or Stickier Glue upgrade.
  • The Cleansing Foam is incapable of directly popping normal bloons.
  • This upgrade removes the camo property from a D.D.T. in Bloons Monkey City.
  • In the Flash version of BMC and in BTD5 Deluxe, the Engineer's Foam has no limit of amount of bloons passing by. This makes the upgrade super powerful, effectively removing all bloon effects if placed at the start of the track.
  • In the mobile versions, the foam lasts for 30 bloons or 8.2 seconds, whichever happens first.
  • In BTD6, there is a specific glob-dispensing sound for Cleansing Foam placement.


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