F*I*R*E,
Yeah, that would be a bad word. Fire prevention is no more difficult then taking a booger outa yer nose, but some folks do love to get it complicated. For an indoor growbox that has caught fire here are your options:
1. dry chemical (not good for this type fire, good for fuel type fire}
2. water (not good for this type fire, good for papertype combustables)
3. Halon ( good for this type fire because of electrical, BUT with WARNING !!
Halon gas displaces the oxygen in the surrounding area thereby putting out the flame, but be most careful that you don't suffocate yourself putting out the fire.
Your all around best advise is think through what your doing, get help from those that have been there and done that. Then go easy at it, watching for potential problems as you put things together.
It's really like flying, 98% of crashes are due to pilot error
smoke in peace
KingKahuuna