Why is Automist a strong option for rebuilding in California’s wildland urban interface (WUI)?

In wildfire scenarios, most homes are not ignited by direct flame contact but by wind-driven embers that travel ahead of the fire front and enter through vents, windows, or other openings. Once that envelope is breached, the fire problem moves inside, where exterior hardening can no longer help and where, in a fast-moving WUI event, no fire crew is likely to be available to intervene.

Automist addresses this risk by rapidly suppressing interior ignition events with minimal water, providing a critical layer of protection once embers breach the building envelope. It can also prevent a small fire within a structure growing out of control and spreading to surrounding buildings. Operating at just 2.4 GPM, around 10% of the water demand of a conventional sprinkler system, Automist places far less strain on water infrastructure while still delivering advanced fire protection.

The sections below explain why each of these properties matters, drawing on recent full-scale fire-spread research and the documented water-supply failures of the 2025 Los Angeles and 2023 Maui fires.

Why is house-to-house spread the real threat in a WUI rebuild?

Post-event investigations of recent catastrophes — the 2018 Camp Fire, the 2021 Marshall Fire, the 2023 Lahaina fire, and the 2025 Los Angeles County fires — consistently find that homes ignite from wind-borne embers and from neighbouring structures, not from a continuous wildfire flame front. Once a community ignites, the dominant failure mode is structure-to-structure conflagration, in which one burning building becomes the heat source for the next.

Full-scale testing has quantified how close is too close. In a 2026 study in Fire Technology, researchers at the Insurance Institute for Business & Home Safety (IBHS), with CAL FIRE support, ran twenty-three full-scale building-to-building burn experiments. They found that at about 10 ft (3 m) of separation a target home had minimal likelihood of survival; only at roughly 20 ft (6 m) did hardened assemblies — noncombustible siding, enclosed eaves, dual-pane tempered windows — begin to meaningfully reduce ignition; and survival improved substantially at 30 ft (9 m). [1] In dense interface neighbourhoods, that protective spacing frequently does not exist, which leaves two practical levers: hardening the envelope, and adding an active intervention at its weakest point.

Why is the window the weak link and why does that move the fire indoors?

Across the IBHS/CAL FIRE campaign, windows were the component that failed most often. In several tests the outer pane detached and the inner pane dropped within the frame, leaving an opening of roughly two inches (5 cm) through which flame or embers could enter the interior. Under extreme wind (50–60 mph), the experiments revealed a previously unobserved failure mode: heat softened the vinyl frame and wind pressure pushed the entire sash inward with both panes still intact — breaching the envelope without the glass ever breaking. ^[1]

The significance for a rebuild is direct: a home can present a fully compliant, fire-resistant exterior and still be lost, because once the glazing fails, radiant heat and embers reach interior furnishings — curtains, sofas, carpets — which ignite and carry the fire into the structure. At that moment the exterior hardening has been bypassed, and the newly burning home becomes a fresh, full-intensity heat source for the next house downwind.

How does Automist perform in a fire compared to traditional sprinklers?

Traditional NFPA 13D sprinklers rely on heat reaching the ceiling to activate a fusible element, by which point a fire is already well developed. Automist uses intelligent detection — a ceiling-mounted detector that triggers a scanning infrared pyrometer to locate the heat source — then directs a targeted, high-momentum watermist blade straight at the fire. ^[2] Fire-engineering research indicates this can activate 2 to 14 times faster than a concealed conventional sprinkler. ^[2]

The mist itself suppresses fire through well-established physics: the very fine droplets (under 100 microns) present an enormous surface area that drives rapid evaporative cooling; as the water flashes to steam it expands roughly 1,700 times, displacing oxygen at the seat of the fire; and the droplet cloud attenuates radiant heat, acting as a thermal barrier. ^[3] That radiant-attenuation effect is directly useful in a WUI rebuild: a mist curtain in the room behind a failed window not only fights an established fire but reduces the radiant flux reaching interior furnishings, helping prevent the ignition that would otherwise follow the breach.

In Practice, this approach:

• Reduces fire growth at an earlier stage
• Limits heat and smoke development within the room
• Uses significantly less water while maintaining effective control

The result is faster response and less overall damage.

Why does water supply matter so much in WUI rebuilds?

Municipal water systems and their hydrants were engineered to fight a fire at one or two structures, not hundreds at once. ^[4] During the January 2025 Palisades fire, the Los Angeles Department of Water and Power reported demand reaching four times normal for fifteen hours straight; the area’s elevated storage tanks were progressively emptied, and by the early morning all had gone dry, sharply reducing flow from hydrants at higher elevations. ^[5] The same pattern recurred in Lahaina in 2023, where firefighters could not find hydrants with adequate pressure and residents’ own hoses ran dry. ^[6]

In many WUI areas, water infrastructure is already constrained. Homes may rely on:

• Smaller service lines
• Limited pressure zones
• Private wells or storage systems

Traditional sprinklers typically require 26–31 gallons per minute, which often triggers water meter upgrades, storage tanks, and pump or pressure-system upgrades. In California these requirements can lead to hidden costs and delays: utilities may require upsizing to a larger meter, involving connection and installation fees as well as higher ongoing monthly charges tied to meter size.

Automist operates at a much lower flow rate and connects to the existing domestic water supply, meaning:

• No large storage tanks are typically required
• No major infrastructure upgrades are needed
• Systems can function even where water availability is limited

Because it draws roughly a tenth of the water a conventional system demands, Automist also places negligible additional load on a network that, during a WUI event, is already running at multiples of its design basis — every gallon it does not draw remains available to hydrants and crews. This makes it far more practical for hillside, remote, or infrastructure-constrained rebuilds.

	Automist	Traditional 13D sprinkler
Flow demand	~2.4 GPM	~24 GPM
Water supply	Existing domestic meter	Often upsized meter / tank
Activation	IR detection, 2–14× faster	Heat-fused element
Pipework at rest	Dry until activation	Commonly charged / wet

Does Automist help with insurance in high-risk fire areas?

Insurers are increasingly focused on risk mitigation and loss reduction, especially in wildfire-prone regions. Because Automist combines early detection with targeted suppression and lower water use, it aligns with the types of mitigation strategies insurers are looking for in high-risk areas. While outcomes vary by insurer, demonstrating enhanced fire protection can support insurability and underwriting discussions.

https://www.privateriskmanagement.org/blog_home.asp?display=48

References

1. Hedayati, F., Gorham, D., Monroy, X., et al. (2026). Wind-Driven Building-to-Building Fire Spread: Experimental Results and Probabilistic Modeling. Fire Technology, 62:32. doi.org/10.1007/s10694-025-01854-3
2. Plumis / Automist technical documentation: scanning infrared pyrometer activation, 2–14× faster than a concealed sprinkler, single-head targeting, ~6 lpm flow.
3. Water-mist suppression mechanisms (evaporative cooling, ~1,700× steam expansion / oxygen displacement, radiant-heat attenuation): Yuen et al. (2023), Fire, MDPI 6(2):40; and related reviews in ScienceDirect and NRC publications.
4. UCLA Luskin Center for Innovation. Do Urban Water Supply Systems Put Out Wildfires? innovation.luskin.ucla.edu
5. Los Angeles Department of Water and Power statements on Palisades Fire water demand and tank depletion, January 2025 (reported via Los Angeles Times / LAist).
6. Water Supply and Firefighting: Early Lessons from the 2023 Maui Fires (2024). Water, MDPI 16(4):600.