Minecraft wiki entry for Defeating_a_Nether_fortress, associated text: Blaze spawners, especially if attached to an often-traversed bridge or corridor, can be a major hazard. You risk being fired at by tons of blazes when passing. Blazes can spawn within 4 blocks of the spawner at light levels 11 or lower, so you can either layer the area with torches, or use more sparsely placed jack o'lanterns, glowstone or shroomlight. The following pattern should work to remove blaze spawns (reused from the amazing Tutorials/Nether Survival guide):