7. Risk Assessment Concepts · Page 2 of 5
Criticality Tiers for Equipment
A simple tier model for SPD rollout.

Tier A — safety / life
Fire systems, emergency lighting supplies, medical, evacuation systems.
Tier B — business critical
Production PLCs, data halls, payment systems, access control for high-security sites.
Tier C — general
Comfort loads and non-critical outlets. Protect at board level first, point-of-use later if needed.
