If susceptibility is known to be less than worst-case protective requirements, which classification is assigned?

• A. HERO safe
• B. Safe separation
• C. HERO unsafe
• D. Eid

Answer: (C)

The key idea is that HERO classifications come from how a item’s susceptibility compares to the protective requirements used for worst‑case conditions. If the susceptibility is known to be lower than those worst‑case protection thresholds, it means the item could be affected by exposure levels that the protective measures are supposed to guard against. In practical terms, even with the protective measures in place, the hazard could still be present, so the item is considered unsafe with respect to HERO. That’s why this situation is labeled as HERO unsafe. The other classifications are used in different scenarios: HERO safe means protection is sufficient to prevent initiation, safe separation is a spacing-based mitigation, and Eid relates to external initiation devices rather than susceptibility comparisons.