What makes ammonia tank decommissioning so dangerous?

“Ammonia remains adsorbed in insulation, weld pores and vapour spaces even after the tank is emptied. Risks include toxic exposure (IDLH 300 ppm), flammability above 16% in air, brittle fracture during cold-tank warm-up (-33 °C inner shell), high-elevation cutting on 30 m double-wall geometry, and contaminated insulation handling.”