In general, a good rule is that once you exceed the PPFD levels of 1000 μmol/s/m2, it should be 1:1 with CO2 PPM, up to 1500. Therefore, at a maximum PPFD = 1500 μmol/s/m2, the CO2 would be 1500 ppm (slightly lower, 1400 ppm may be the safest to start with).
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