The canyon is deep from the beginning, and often contains a few muddy pools near the entrance after which the passageway is dry for a while. The walls become as little as 2 feet apart and the rocks above curve inwards preventing all but occasional rays of sunlight from illuminating the way ahead. In a particularly narrow and gloomy section there is likely to be a long, thin pool of cold water, 5 feet deep or more, that curves around several bends in the canyon but apart from this there are no major obstacles before a temporarily wider, shallower and more brightly lit section filled with fallen rocks - a subway-like chamber that often harbors one or more small rattlesnakes. These creatures are frequently found in canyons in this region, and are usually the midget faded species, a regional variation of the western rattlesnake; pale yellow in color without any distinctive patterns.
Beyond the open area, the gulch deepens again and soon becomes too narrow to continue at ground level - the passageway is about 6 inches wide and offers no easy way to climb above the tight section, so returning back to the entrance is the only option for most people. This turn-around point is reached about 20 minutes hiking in the narrows. The lengthy central section of Brimstone Gulch can best be traversed starting from the upper end, by use of chimneying techniques several meters above the floor, and a number of small rappels.