After mixing fresh soil, wait days to weeks then reach into the middle with your hand or a thermometer. If the middle is hot (above ~90F), the composting process is still active — don't plant in it yet. Mix the cool outer material into the hot middle and let it cool again. Below ~1 cubic yard the risk is low; above that or combining multiple kits makes hot spots more likely.
'If it's hot to the touch with your hand in the middle you probably don't want to use it yet.'
Discussed in: Ep 003