I want that while the furnace is melting it will deal damage to the player

i tried using different triggers
on smelt: - does not work
on fuel burn: - does not work
on join: - works all the time, even when it is not melting

Code (Text):

1. on smelt:
2.     wait 1 tick
3.     while player is alive:
4.         loop all blocks in radius 1 around the player:
5.             if loop-block is a furnace:
6.                 damage player by 0.5
7.         wait 1 second