That phrase is the Safeguard, and Season 3 is finally forcing viewers to reckon with exactly what it means for Juliette, Lukas, and the 10,000 people trapped underground with her. The Safeguard Procedure is the ultimate failsafe built into every silo, and understanding it is key to understanding where this Apple TV Plus sci-fi drama is headed next. What the Safeguard Procedure Actually DoesAt its core, the Safeguard Procedure is a contingency plan in case a silo revolts, allowing some unseen entity to kill every single person in the silo via a pipe full of poison that gets distributed through the vents. Apple StudiosThe Safeguard is described as the fail-safe, a pipe on Level 14 designed to gas an entire silo’s population the moment things get out of hand. Why the Safeguard Still Haunts ‘Silo’ Season 3Season 3 has made clear that knowing about the Safeguard is not the same as being able to stop it.