In-line fan w/ carbon scrubber is what the man is talking about (i think?).
Extra equipment for summertime hydro consists of 1-12,000 BTU- A/C, 1-Reservoir chiller, 1-460 CFM In-line exhaust for 2-1000's watt HPS w/ vented hoods / glass. Lights have seperate air intake / exhaust. That's it...