be fine - i've also read that its goood to open your gas cap to releave the pressure - but the xtinquishers i sold should put out a decent size engine fire and will leave no mess
i honestly dont know the exact right/best way to put it out though
1990 300ZX TT w/ some mods 1999.5 Audi A42.8Quattro supercharged 1998 CBR 900RR