The one fire metric that is genuinely comparable across every Maryland county is the civilian fire-death rate: average annual civilian fire deaths per 100,000 residents over 2020-2024. Deaths come from the Maryland State Fire Marshal's fatality report (an un-suppressed county breakdown); population comes from the U.S. Census Bureau. The rate is a direct, reproducible calculation —(5-year deaths ÷ 5) ÷ population × 100,000— not an estimate.

The Overall Fireground Index score normalizes that rate across the 24 county-equivalents: a z-score, inverted so a lower fire-death rate yields a higher score, centered at 50and clamped to 0-100:score = clamp(50 − z × 18, 0, 100). There is no black box. The platform's multi-dimensional scoring engine is reserved for when multiple comparable metrics exist; with one comparable fire metric today, this single transparent normalization is used instead.

Where a county publishes an incident/response figure, it is shown as sourced context with its exact definition and reporting year. These counts use incompatible definitions across counties (total responses vs. EMS-only vs. per-station), so they are never normalized into a cross-county comparison — that would be misleading.

Civilian injuries, firefighter injuries, and fire dollar loss have no authoritative per-county public source, so they are shown as "Data not publicly available"with the sources investigated. Missing data reduces Data Confidence; it never blanks a county.

Data Confidence communicates how much verifiable public evidence backs a county: the authority of its sources, how many public metrics exist, and how statistically reliable the outcome data is (a county with 0-2 fire deaths over five years has a real but uncertain rate). A data-rich county reads differently from a data-sparse one — and that difference is itself information. Confidence is never based on whether every county reports identically.