File:Blazespawner.png

Summary
Minimum light required to disable blaze spawner based on how visible/uncovered it is:

Only top of spawner visible: 4 glowstone or 8 torches. Entire spawner visible: 8 glowstone or 32 torches. 1 air layer beneath spawner: 32 glowstone or 64 torches. 2 air layers beneath spawner: 64 glowstone (not possible with torches). >2 air layers beneath spawner: not possible.