As additional clarification if you align the piece upward to look like this then you're fine:

   #
  ##
  #

You'll end up with

   # # # # #
  ##########
  # # # # # 

which becomes

   # # # # #
  # # # # # 

which you can just repeat over and over again forever (if your variant of Tetris includes gravity even this collapse to nothing).