A surgical tray is autoclaved at 121°C for 15 minutes before the operation. Steam under pressure (121°C, 15 psi) kills everything including spores — the gold standard for surgical instruments; indicators (chemical strips, biological spores) verify each cycle. Heat-sensitive items (plastics, endoscopes) use ethylene oxide or glutaraldehyde. The sterile field is surgery's invisible foundation — every infection prevented starts with this cycle.