The red chem light marks the edge of the viewing area for special guests. I inadvertently found myself shooting from an absolutely amazing position while shooting The Procession of the Ceremonial Flame.
It was literally not possible to be any closer to the effigy without being a member of the fire team. I ended up curling myself into a ball to escape the heat and keep shooting.
Burning Man: Cargo Cult, August 31, 2013