Pyrotechnics turns a fire into either a burst of blinding fireworks or a thick cloud of choking smoke, depending on the version the character chooses.
Fireworks: The fireworks are a flashing, fiery, momentary burst of glowing, colored aerial lights. This effect blinds creatures within 120 feet of the fire source for 1d4+1 rounds (Will negates). These creatures must have line of sight to the fire to be affected. Spell resistance can prevent blindness. In addition to the obvious effects, a blinded creature suffers a 50% miss chance in combat (all opponents have full concealment), loses any Dexterity bonus to AC, grants a +2 bonus to attackers' attack rolls (they are effectively invisible), moves at half speed, and suffers a -4 penalty on most Strength- and Dexterity-based skills.
Smoke Cloud: The smoke is a writhing stream of smoke billowing out from the source and forming a choking cloud. The cloud spreads 20 feet in all directions and lasts for 1 round per caster level. All sight, even darkvision, is ineffective in or through the cloud. All within the cloud suffer -4 penalties to Strength and Dexterity scores (Fortitude negates). These effects last for 1d4+1 rounds after the cloud dissipates or after the character leaves the area of the cloud. Spell resistance does not apply.
Material Component: The spell uses one fire source, which is immediately extinguished. A fire so large that it exceeds a 20-foot cube is only partly extinguished. Magical fires are not extinguished, although a fire-based creature used as a source takes 1 point of damage per caster level.