how close is to close?

for my whole last grow my light was attatched to the roof of the grow room and the plants grew great but I was wondering how close is to close?

You're gonna have to tell us what type of light you're using and what wattage it is.

holy fuck shoulda thought of that hahah

250 Watt HPS Grow room is about 4 maybe 5 feet tall 3/4 feet wide