How HFS Works
A full engineering deep dive into the Honolulu Fire Shield.
The Threat Model
Ember Storms — Burning embers travel 30–60 minutes ahead of the fire front, carried by wind up to several miles. These embers land on roofs, in gutters, on decks, and in vegetation, causing spot ignitions that destroy homes before the main fire arrives.
Radiant Heat — Intense radiant heat from approaching flames can ignite combustible materials through windows and thin walls at distances of 30–100 feet, depending on fire intensity.
Direct Flame Contact — The last threat to arrive, but often the most publicized. Research shows that most home losses are actually caused by embers, not direct flame — making early suppression the highest-value intervention.
5-Layer System Architecture
From satellite detection to water on target — a fully integrated defense stack.
Zone Breakdown
Total simultaneous demand: 48.0 GPM across all 4 zones.
Zone 1 — Roof Rotors
6 heads × 2.0 GPM = 12.0 GPM, min 30 PSI
Impact-style rotary sprinklers mounted at roof peaks. Provide continuous wetting of the entire roof surface to prevent ember ignition of roofing materials.
Why this matters
The roof is the largest ember-collection surface on any home. Keeping it wet eliminates the #1 ignition pathway.
Zone 2 — Eave Sprayers
16 nozzles × 1.2 GPM = 19.2 GPM, min 20 PSI
Fine-mist nozzles installed along eave lines. Create a water curtain protecting the most vulnerable ignition point — where embers collect in gutters and soffits.
Why this matters
Embers are pushed into attic spaces through soffit vents. The mist curtain intercepts them before they reach these openings.
Zone 3 — Foam / Deck
6 foamers × 0.8 GPM = 4.8 GPM, min 20 PSI
Class-A foam applicators (0.3% concentrate, USFS approved, biodegradable) for decks, fences, and combustible attachments. Foam increases water's effectiveness 3–5x.
Why this matters
Foam clings to vertical surfaces where water would run off. A single application protects for 6–12 hours.
Zone 4 — Perimeter
8 heads × 1.5 GPM = 12.0 GPM, min 25 PSI
Ground-level sprinklers creating a wet perimeter around the structure's defensible space. Addresses radiant heat and ground-level fire spread.
Why this matters
Wet vegetation is dramatically harder to ignite than dry brush. Covers the 30–100 ft defensible space zone recommended by NFPA and CAL FIRE.
Hydraulic Validation
All 4 zones were modeled and validated in EPANET 2.2 hydraulic simulation software. The system passes at both operating conditions:
100 PSI
Municipal Mains Supply
ALL ZONES PASS
60 PSI
10,000 gal Backup Tank + 2HP Pump
ALL ZONES PASS
Backup supply: 10,000-gallon HDPE tank with 2HP centrifugal pump (50 GPM max). Runtime target: 12 hours continuous operation.
Detection Layer
NASA FIRMS
<60 sec latency
Satellite-based hotspot detection using MODIS (~25 sec) and VIIRS (~50 sec) instruments. Ultra Real-Time data for the continental US.
NOAA Weather API
12–24 hr advance
Red Flag Warnings provide advance notice of extreme fire weather conditions, enabling pre-positioning and system readiness checks.
Local Sensors
Fail-safe backstop
On-site thermal sensors (trigger at >140°F) provide a last line of detection if cloud-based services are unavailable.
Hawaii Fire Activity
Loading…Activation Logic
Level 1 — Alert
Fire detected within 7 miles. System enters readiness mode. Homeowner notified via SMS. Backup pump primed.
Level 2 — Activate
Fire within 2 miles OR local sensor reads >140°F. All zones activate automatically. Full 48 GPM deployment.
v1 Prototype — Reference Property
Interactive site plan for the HFS v1 Prototype installation at 1668 Onipaa St, Honolulu. DXF-verified geometry with toggleable zone layers, full head schedule, and installation notes.
Open Interactive Prototype →Bill of Materials
Complete component list with specs, quantities, and estimated costs — available on the Open Source page.
View Full BOM →Real-World Validation
Exterior sprinkler systems have been documented saving homes in 6 major wildfire events. Each case below links to a full analysis with documented evidence, scientific context, and engineering takeaways.
Ham Lake Fire, Minnesota
Cabin owners with roof sprinklers survived while 144 structures were destroyed across 75,000 acres.
Read full analysis →Cedar Fire, San Diego
Only homes with active exterior wetting survived on some streets. 2,820 structures destroyed across 273,000 acres.
Read full analysis →Camp Fire, Paradise CA
95% of 18,804 structure losses caused by embers — not flame. Homes with roof sprinklers were among the few survivors.
Read full analysis →Roosevelt Fire, Wyoming
Automated sprinkler system protected a home with zero damage while owner was evacuated. Fire burned to within 10 feet.
Read full analysis →Woolsey Fire, CA
Modern WUI code-compliant homes were destroyed. Only homes with active exterior wetting survived in hardest-hit areas.
Read full analysis →Korean Forestry Research
Peer-reviewed: 70%+ fire spread suppression within 60 minutes, 50% smoke reduction, fuel moisture above 200%.
Read full analysis →