Here is the full list of all 15 Chill the Piro achievements.
Save 150 dwellers
Quench 1000 fires
Collect 25 dynamites
Try and see all Piro advice
Pass a level without using extra time (where it exists)
Get all gold medal
Complete the story mode
Burn the fireman in the Piro game mode.
Complete the Piro game mode
Throw dynamite in fire
Start the new story and complete it without quit the game.
Test the effect of all the machinations of Piro
Pass the level without use the bucket
Wait until appear 3 Piro