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

Wildfire-resistant construction is designed to keep fire out of your home, and that should always be the first line of defence. Ember-resistant vents, appropriate glazing, roofs and eaves, defensible space and vegetation management all reduce the chance of ignition.

But severe wildfire exposure can still breach the building envelope. Windows can fail, embers can enter through openings, and fire can find its way inside. When that happens, Automist gives the home another opportunity to survive.

Automist detects a developing interior fire, locates it and targets it with water mist using just 2.37 gallons per minute (approximately 2.4 gpm). Its first job is simple: stop or slow the fire before it develops into a whole-house fire.

What happens if wildfire hardening is breached?

Full-scale WUI research has shown why this second line of defence matters. In recent building-to-building fire experiments, windows were an important vulnerability: heat could damage glazing and frames, while strong winds could help create openings through which fire and embers could reach the interior. Once the envelope is breached, furnishings and other contents can ignite even when the exterior of the home has been carefully hardened.

At that point, exterior hardening has done everything it can. The problem has become an interior fire, which is precisely what Automist is designed to detect and suppress. In a major conflagration, where firefighters may be responding to many structures simultaneously, automatic intervention also means the home does not have to wait for a crew to arrive before suppression begins.

Why does earlier suppression matter?

Conventional residential sprinklers rely on sufficient heat reaching the sprinkler at ceiling level before its thermal element operates. Automist uses smoke detection and infrared sensing to locate the heat source and direct water mist at the fire.

In controlled experiments with slower-growing fires, Automist activated between 2 and 13.7 times faster than concealed residential sprinklers. The work was subsequently published in Fire Safety Journal and modelled in B-RISK so that the activation characteristics could be represented computationally.

The practical benefit for a homeowner is straightforward: the earlier the fire is attacked, the greater the opportunity to keep it small and prevent the home becoming fully involved.

Automist’s fire-suppression performance is not a theoretical WUI proposition. It is an existing UL 2167A Listed residential water-mist system, designed specifically to detect, locate and control residential fires.

What if wildfire creates more than one fire inside the house?

through different openings, windows can fail in separate rooms and fires can potentially develop at more than one location.

This is where Automist’s very low water demand becomes particularly useful. A conventional NFPA 13D system is normally hydraulically designed around up to two operating sprinklers. If additional heads operate, they place additional demand on the available supply. NFPA 13D’s standard design approach reflects the expectation that residential fire suppression normally deals with a limited fire area rather than multiple independent ignitions throughout a home.

Each independent Automist system, by contrast, requires only 2.37 gpm. Independent systems can therefore be configured to protect different vulnerable areas of a property while remaining within a relatively modest overall water demand.

That gives a property much more flexibility to use its available water against separate fires rather than rapidly consuming its supply through a small number of high-flow outlets.

The individual suppression capability exists today. What we are interested in researching further is how much this low-flow, distributed approach could improve overall resilience when a property is exposed to multiple wildfire-driven ignitions simultaneously.

Why does water efficiency matter during a prolonged wildfire?

Wildfire exposure can last much longer than a normal residential fire event, so making the available water last matters.

This is particularly obvious where the suppression system relies on stored water. NFPA 13D generally requires the design flow to be available for 10 minutes, subject to specific permitted exceptions. That means a tank supplying a conventional residential sprinkler system is intentionally designed around a relatively short period of operation.

Automist’s default suppression run is 30 minutes, yet it requires only 2.37 gpm. Because the flow is so low, a finite water supply can provide considerably more useful suppression time. The system is also electronically controlled: after its operating period it stops, and if fire demand subsequently returns it can operate again.

That is particularly relevant to wildfire, where the exposure may come and go. An ember could cause an interior fire, Automist could control it, and another ignition could occur later. Rather than consuming the available water continuously simply because the system activated once, Automist can preserve that resource for when there is actually a fire to fight.

What if the house is ultimately overwhelmed?

No suppression system can guarantee that a house will survive every possible wildfire exposure. If a structure is eventually overwhelmed, however, the way the suppression system behaves can still matter.

A conventional sprinkler head is mechanically opened by heat. Once it operates, it remains open until someone isolates the water supply. Additional heated heads can also operate. If the property is evacuated and the structure is ultimately lost, those open outlets do not know that the building can no longer be saved.

This has happened in a real conflagration. During NIST’s reconnaissance of the 2017 Tubbs Fire, investigators observed residential fire-suppression systems continuing to discharge in homes that had burned to their foundations. NIST reported that this contributed to loss of water pressure and made it harder for firefighters to extinguish other fires.

Automist behaves differently. Its high-pressure suppression pipework is dry in standby and discharge is pump-controlled and normally closed. It does not remain permanently hydraulically open simply because it activated earlier. Once its suppression period ends, it stops; if fire demand subsequently returns, it can respond again.

Damaged domestic plumbing can of course still leak if a house is destroyed, regardless of the suppression system installed. The distinction is that Automist does not inherently add the same persistent suppression-specific demand from sprinkler heads that have mechanically latched open.

Could protecting one home also help protect the next?

For the homeowner, the objective is to save the house. But there is a wider benefit to doing that successfully.

Once a structure becomes fully involved, it can become an intense source of heat, flame and embers for neighbouring properties. Recent full-scale research involving 23 wind-driven building-to-building fire experiments has demonstrated how strongly separation distance and the intensity and duration of the source-building exposure influence the survival of the neighbouring structure.

That makes stopping the first house important beyond its own property line. If Automist controls an interior fire before full involvement — or keeps it smaller for longer — the home does not become the same fire exposure to its neighbour.

The underlying suppression mechanisms are already established. What we now want to quantify is the community-scale effect: how much earlier, low-flow suppression could slow the transition from one burning house into a broader structure-to-structure conflagration.

Why could lower water demand also matter to the community?

During a major conflagration, many different demands compete for the same water network. Firefighters are using hydrants, building suppression systems may be operating and damaged properties can continue releasing water even after they have been lost.

Recent wildfire water-system research has shown that these accumulating property-level losses can materially accelerate depressurisation and reduce how long useful firefighting water remains available. This means the amount of water required by each individual property becomes important when the same event is repeated across hundreds of homes.

Automist uses approximately one-tenth of the water of a typical two-head conventional residential sprinkler design, while its controlled discharge avoids remaining permanently open after activation.

Across one house that difference is useful. Across an entire neighbourhood it could become much more significant.

This is the second area we are now interested in quantifying: how much community water pressure could be preserved when homes use low-flow controlled suppression instead of substantially higher, persistent suppression demand.

*Illustrative NFPA 13D residential sprinkler demand; actual system design varies.
† Representative exterior-sprinkler flow rates discussed in the wildfire sprinkler research; system designs vary considerably.
‡ 1,000 gpm is an illustrative fire-flow requirement for a dwelling fire, rather than as a universal requirement.

Does the same low flow make rebuilding easier?

Yes. The water-supply problem often begins long before a wildfire.

Conventional residential sprinklers can require flows that exceed what an existing domestic connection was designed to provide. Depending on the property and utility, that can mean a larger meter, upgraded service line, additional storage or pumping equipment.

Automist requires only 2.37 gpm, allowing it to work with a conventional domestic water supply in many properties and potentially avoiding substantial water-infrastructure upgrades. That can be particularly valuable for hillside, rural and infrastructure-constrained rebuilds where increasing available flow may be difficult or expensive.

The same characteristic therefore provides value twice: less infrastructure may be needed to protect the home, and the available water lasts much longer when protection is actually required.

How should Automist fit into a WUI rebuild?

Automist should complement wildfire-resistant construction, not replace it. The best outcome is still to prevent wildfire from entering the building in the first place.

But no individual mitigation measure is perfect. If the exterior envelope is breached, Automist provides an active second line of defence that is already available today: detect the fire early, target it, use very little water and keep the available water working for as long as possible.

For a homeowner rebuilding in a WUI area, the logic is simple:

Keep wildfire out if you can. If it gets in, stop it as early as possible. Make the available water last. And give your home every possible chance of surviving.

The wider opportunity comes from repeating that principle across a community. If more homes can stop or slow interior fires before becoming fully involved — while consuming much less water in the process — there is the potential to both slow house-to-house conflagration and preserve more water for the homes and firefighters still in the fire’s path.

Those community-scale effects are what we are now working to better understand and quantify.