I think they mean fans like this: https://www.amazon.com/dp/B07ZJ47Z2J/ref=cm_sw_r_apan_i_RM0BGFCZXPSER79MW0EN?_encoding=UTF8&psc=1

Personally, I have a large wire rack with those same Barrina grow lights but they are 4ft long. Since the rack isn't enclosed there is some degree of constant air circulation but I still get occasional mold and disease issues with my microgreens and seedlings. When I turn the ceiling fan on it definitely seems to help alleviate these issues. So I also recommend getting a small fan or two for an enclosed setup like that.