What Is a Fire Hazard Severity Zone (FHSZ)?

Before Zone 0, before defensible space, before any of California's wildfire-safety rules apply to a property at all, there's one underlying classification that determines whether they reach you in the first place: your Fire Hazard Severity Zone, or FHSZ. Here's what it actually is, how it's determined, and what it triggers.

What a Fire Hazard Severity Zone measures

A Fire Hazard Severity Zone is a classification the State Fire Marshal assigns to land based on fuel loading, slope, fire weather, and other physical conditions - including areas where wind is a major driver of fire spread. Every parcel gets sorted into one of three classes: Moderate, High, or Very High.

The distinction worth understanding clearly: FHSZ measures hazard, not risk. Hazard reflects the physical conditions and expected fire behavior over a 30-to-50-year period, without factoring in mitigation - your FHSZ tier doesn't change because you've hardened your home or cleared brush. Risk is the potential damage under current conditions, accounting for those mitigations. Think of it the way a flood-zone map describes probability of inundation, not a prescriptive damage forecast for one specific house.

Gov. Code §51178 / PRC §4202

State Responsibility Area vs. Local Responsibility Area

The other classification that matters alongside your hazard tier is whether your property sits in a State Responsibility Area (SRA) or a Local Responsibility Area (LRA) - which agency has legal responsibility for wildfire prevention and suppression where you live.

SRA maps are adopted directly by the state. The current maps were adopted January 31, 2024 and took effect April 1, 2024. Every SRA parcel falls into one of the three hazard tiers - there's no "unzoned" category within SRA.
LRA maps work differently: CAL FIRE issues them as a recommendation, and each local jurisdiction's governing body has to formally adopt them by ordinance before they're legally in effect - generally within 120 days of the state's recommendation. The current LRA maps were recommended March 24, 2025, with most local adoptions following through mid-2025, though the exact date varies by city and county. A property can sit in a "Recommended" LRA zone that hasn't been formally adopted yet, which is a meaningfully different legal status than an already-adopted one.

PRC §4125 / Gov. Code §51175 / SB 63 (2021)

Statewide rule applies (SRA - any tier, or Very High LRA)

Statewide rule doesn't reach it (Moderate/High LRA, or no FHSZ at all)

Local ordinance - a separate, independent possibility

You shouldn't have to work this out yourself That chart is a big part of why Zone Zero Check exists. Knowing whether your property is in the SRA or LRA, which of three hazard tiers it falls into, and whether your specific city or fire district has layered on its own ordinance isn't something a homeowner should have to piece together from state, county, and city sources one at a time. Enter your address and we run that entire determination for you against CAL FIRE's current maps - no flowchart required.

What your FHSZ tier actually triggers

This is the part that makes your specific classification matter in practice, not just as a label:

The 100-foot defensible space requirement (Zone 0, Zone 1, and Zone 2, covered in our breakdown of all three) applies to any SRA property, and to Very High LRA properties specifically - Moderate and High LRA aren't reached by this requirement.
Zone 0, the newly-adopted five-foot ember-resistant zone, follows that same SRA-any-tier / Very-High-LRA scoping. See our Zone 0 explainer for what it actually requires.
California's Wildland-Urban Interface building code (Chapter 7A - fire-resistant roofing, siding, decking, vents, windows) applies to new construction anywhere in SRA, and to new construction in High or Very High FHSZ within LRA.
The real estate disclosure requirement under AB 38 applies to any property in a High or Very High FHSZ, regardless of SRA or LRA - see our AB 38 explainer if you're buying or selling.

Local jurisdictions can require more

Everything above is the statewide floor, not the ceiling. A handful of California cities and fire districts have adopted their own, stricter local ember-resistant-zone ordinances - independent of, and sometimes reaching further than, the SRA/LRA/tier determination above. San Diego and Berkeley are two we've verified against a primary source; several more exist.

A local ordinance can matter in two different ways: it can tighten the state's own requirements for a property already in scope, or it can reach a property the statewide rule doesn't - a Moderate or High LRA parcel the 100-foot requirement above doesn't cover can still be bound by a city's own rule. Check your county's page to see if one applies where you live.

Find your own property's zone

Your FHSZ tier and SRA/LRA status are the two facts that determine which of California's wildfire-safety requirements actually reach your specific address - not your county, not your city, your parcel. Enter your address below for a free, real-time lookup against CAL FIRE's own current hazard zone data.