hot zone

noun3

1. •
   An area to which access is restricted because it is contaminated with radiation or a chemical or biological biohazard.

   • Medical monitoring is an essential aspect to conducting operations in the hot zone. — 2004
2. •
   An area where fighting or hostilities are likely to erupt.

   • Any spot I could point to on a map was about to turn into a hot zone. There was too much trougle brewing for it not to bubble over, and by the summer of 2012, I had a major decision to make. — 2014
3. •
   An apparatus for growing crystals at very hot temperatures.

   • The “hot zone” is the key part in controlling the growth process, the melt and gas flow, and the concentration of the intrinsic point defects and their aggregates. — 2014