Not sure about code or cannabis, but you might want to have some kind of exhaust in order to control CO2 levels to its optimum range.
CO2 is usually added to vegetables greenhouses to increase yield.

Code doesn’t specifically require exhaust for cannabis cultivation itself. But some of the supporting elements of the operation like CO2 use and making sure you have protections and purge capabilities during accidental release would end up indirectly leading you to exhausting certain areas that use it. Or odor control may lead you to maintaining certain areas at a negative pressure via exhaust fans. Where it’s grown usually isn’t an occupied space if people only spend small increments at a time in there, so ventilation isn’t directly required, but some detection and alarm system to protect on high CO2 would be. NFPA 45 is probably a good reference about gas use and projections required.