Catching On Fire
Characters exposed to burning oil, bonfires, and noninstantaneous magical fires might find their clothes, hair, or equipment on fire. Spells or technological items with an instantaneous effect don’t normally set a character on fire, since the heat and flame from these come and go in a flash.
A character at risk of catching fire must succeed at a Reflex saving throw (usually DC 15) or gain the burning condition (see page 273). Those whose clothes or equipment catch fire must attempt a separate Reflex saving throw (at the same DC) for each item. On a failed saving throw, flammable items take the same amount of damage as the character.
Source
Core Rulebook pg. 403