what wattage lamp is the safest to use in my tent.

Hey roll it upers,,,I have a Secret Jardin Dark street DS90 11 Tent,,,The dimensions are 90cm x 90cm x 160cm. I was wondering what the highest wattage lamp would be the safest to use in it.At the moment im using a 250w sodium in it (recommended by the manufacturer) but was wondering if it would be safe to go higher? Has anyone out there ever had any horror stories by using a stronger lamp than the tent can handle???.As usual all reply's welcome.Peace.

I wouldn't go bigger than a 600W in that tent. You are going to have to keep it well ventilated so keep that in mind when you are shopping.