CO2 Enrichment for Increasing Yield

I've been reading up on how increasing the co2 creates a tremendous increase in yield.
Is there an optimal ppm for the amount of co2 in your room? What ppm do you set your room at and can you state the increase of yield you got from adding a co2 generator to your grow room?

I'm not exactly sure if Im correct but from what I have been reading is that the PPM should be around 1500 during the on light hours.