I would say 3 feet hallways is the minimum, I would even go 4 in the home or yard haunt situation. Just because the walls outside are not nearly as sturdy as real walls, so the people have pleanty of room to jump without crashing into my walls and wrecking my haunt, and me being sued. Also, do whatever you want for lighting, but remember to light up the ground for people to walk.
For the angle grinder.... did you want it as just a sound thing or to grind metal and make sparks? Number one, it will draw alot of power on a standard outside house electrical system, when using foggers and lights with it. Also, a spark fence would be alot safer (no metal filings flying into peoples eyes ), I believe there's plans on haunt project. You basically take a auto battery charger, hook up the ground to the metal fence, and take the positive, hook it up to a piece of metal rod or something. And you basically scrape the fence w/ the pos. side to make sparks. CAUTION!!! Make sure you have wide paths so people don't get sparks on them. DO NOT HOLD THE POSITIVE ON THE FENCE FOR TOO LONG!!!! It will WELD IT SELF TO THE FENCE. Also, make sure you are wearing gloves, and the operator has to make sure NO ONE is touching the fence or they'll get shocked. You may even put a thin sheet of plexi glass on the outer side of the fence so no one can touch it, but you still get the effect. Light this with dim red or orange light (homemade LED spotlights work good) so it is just the actor's shadow, then, target the middle part of the group to start doing the sparks with. Maybe even hook up a mini strobe on a switch that you can flick on quickly, to light up the path with, to give it more of an effect. Set the flash speed so it simulates sparks. A red or blue gel on the strobe may look cool too.
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