Often 50 ft wide and 120 ft long.
Used as extra juggling space when the gym is too small, and normally used for the bar.
Often provided by Jeff Dobson, he knows what to expect and is relaxed about hiring to a BJC. He won't ask for references or deposits etc.
They also need fire exit signs. From every indoor location (which includes marquees) there must be at least one fire exit sign visible. This sign must be illuminated in some way even if the main power goes out. Battery backed fire exit signs are the normal way to do this. The marquee supplier can probably bring some, remember to ask for them!
If the fire service become aware of the event they may send round an inspector, who will be checking these things, and who has the authority to close down your whole event.
British Standard 5499-4:2000 covers fire safety signs.
Marquees need to be fixed down securely, traditionally this is done with metal stakes which are approximately 30 inches long. Consider what could be underground when you site your marquee, electrical cables, data cables, etc can be found less than 3 feet deep.
Also if the marquee is sited on tarmac or concrete, then any holes created will need to be filled/repaired afterwards.
BJC Huddersfield solved this problem by using water butts to secure the marquees, these butts held 1 ton of water each and 16 were used for the 110ft long marquee.