Brazier Lock

Perfectly cut stone interrupts the natural cave wall. Within seconds the meandering hall gives way to a rigidly circular room, ever-burning flames lazily burning above, and a cold brazier sitting at the center of the floor. A thin trough below it runs directly to a riveted metal door while four other troughs disappear under four other wooden ones. Within each of these rooms is yet another cold brazier. There is little doubt that these all must be lit to open what is clearly a magically locked door.  Now only remains one question: how are the brazier to be lit?