Understanding PVSTOP for Fire Safety in Public Buildings
PV Fires in Public Buildings: PVSTOP On-Site vs PVSTOP with the Fire Department vs No PVSTOP
Rooftop solar PV has become part of the building. That means PV changes the fireground, even when PV didn’t start the fire. Research and firefighter training resources consistently highlight the same operational reality: PV can increase electrical shock/arc risk, complicate roof access/ventilation, and create uncertainty about what is truly de-energized.
When incident commanders apply ICS priorities—Life Safety → Incident Stabilization → Property Conservation—PV mainly impacts the stabilization phase: controlling the hazard and reducing responder exposure.
This article compares three readiness models for high-occupancy sites like hospitals, schools, shopping malls, hotels, stadiums, airports, municipal buildings, and large commercial premises.
Why PV changes “normal” fire response
Most responders are trained to isolate power, but PV introduces a crucial twist: shutting down AC mains or the inverter does not automatically mean the PV array is electrically safe, especially in daylight and especially if components are damaged. Fire service training material emphasizes “isolating power,” “covering panels,” and the hazards of damaging PV with tools—because these issues come up in real incidents.
Also: “covering” methods must be handled carefully—UL/FSRI documentation specifically warns that wet tarps on damaged equipment can become energized and conduct hazardous current.
So the question for building owners and insurers becomes:
How quickly can this site reduce PV-generated electrical hazard—without guessing—so responders can stabilize the incident and safely hand over the scene?
The ICS lens (what we’re trying to achieve)
In ICS, the field priorities are typically:
- Life Safety
- Incident Stabilization
- Property Conservation
PVSTOP fits best under Incident Stabilization (reducing ongoing electrical hazard at the source) and Property Conservation (helping make the site safer for handover and re-entry), while always supporting Life Safety by reducing risk exposure, when used within a trained SOP and incident command direction. UL FSRI training and research repeatedly highlight limitations of disconnect devices, covering/de-energizing practices, and tactics that reduce responder exposure around PV.
What PVSTOP is (in plain terms)
PVSTOP is described by manufacturers/distributors as a light-blocking “liquid tarpaulin/blanket” applied to PV module glass to interrupt generation at the source. (In other words: if light is the fuel for PV electricity, block the light to reduce/stop output.)
Its published safety guides also describe handling, cleanup/disposal considerations for the dried film.
(Important: PVSTOP is not a substitute for compliant design, labeling, accessways or firefighter training. It’s a response tool that works best inside an ICS-aligned plan.)
The three real-world options (and why they’re not equal)
Option A — PVSTOP stored ON SITE (facility-owned)
What it means: The hospital/school/mall/hotel keeps PVSTOP on-site (e.g., security control room, fire panel area, plant room), with a trained internal team and a documented SOP that integrates with the responding fire department.
The benefits
- Time-to-effect is the big win. Any delay in hazard reduction can mean more escalation, larger cordons, and more defensive tactics. On-site storage eliminates “wait for special equipment to arrive.”
- Better ICS integration on arrival. The Incident Commander can quickly decide: “Do we deploy the de-energizing method?” without it being dependent on a later resource.
- Supports safer stabilization and handover. PV hazards can persist into overhaul/re-entry. A site-held capability helps move toward “safe enough to work” sooner.
The non-negotiables (or it becomes theater)
- Clear signage + roof plan + isolation points + contacts (so crews don’t “hunt” during an incident). NFPA and other best-practice guidance emphasize PV marking/access and firefighter operational impacts.
- A written SOP that says who may deploy it, when, under whose authority (IC), and how the area is controlled during application.
Best fit
- High-occupancy / high-consequence sites: hospitals, clinics, old-age homes, schools, shopping malls, hotels, airports, stadiums, large municipal buildings.
Option B — PVSTOP held by the FIRE DEPARTMENT (or metro cache)
What it means: PVSTOP is stocked on specific pumpers/response units, at stations, or as a special resource that can be dispatched.
The benefits
- Standardization across many sites. Great when you can’t guarantee every building owner will invest.
- Training consistency. The fire service can control training, deployment rules, and after-action learning.
- Good for extended incidents. If the incident is prolonged, a fire-service cache can still be decisive during later stabilization/overhaul phases.
The limitations
- It’s still a response-time problem. In the early minutes, crews may already be making defensive decisions because PV hazards remain unresolved.
- Competing demand. One cache may be needed across multiple incidents.
Best fit
- Municipal strategy for a metro with widespread PV adoption, especially where building owners vary greatly in capability.
Option C — NO PVSTOP (status quo on many sites)
What it means: The plan relies on conventional shutdown steps, exclusion zones, and tactics that assume parts of the array may remain energized and roof options may be constrained.
The reality
- Many guidelines stress that PV systems can introduce shock/arc hazards, affect water application considerations, and can complicate operations, especially if the system is damaged.
- Practically, this can mean bigger cordons, more defensive posture, longer downtime, and tougher handover conditions—particularly on large arrays or complex roofs.
Best fit
- This condition should be treated as residual-risk acceptance. Controls such as labeling, accessways, isolation, competent O&M, and responder training reduce exposure, but they do not remove generation. Therefore PV remains an energized hazard in daylight, and safe re-entry / “all clear” decisions require stricter thresholds and longer stabilization periods..
Word-ready comparison table (copy/paste)
| PVSTOP on site | Fastest access; strongest support for incident stabilization; better chance to make the site safe for handover | Requires onsite SOP + training + storage control + signage/plan | Hospitals, schools, malls, hotels, any high-occupancy public place |
| PVSTOP with fire department | Consistent capability across the city; FD-controlled training; useful for long incidents | Travel/dispatch delay; may arrive after key early decisions | Metro-wide coverage where owners vary in readiness |
| No PVSTOP | No procurement/training burden | Fewer stabilization options; PV hazards may persist; more operational constraints | Residual-risk acceptance only, procedural controls and exclusion zones; “electrically safe” may not be confirmable. |
The “insurance question” (what underwriters and risk managers care about)
A credible PV fire readiness story is not “we have a product.” It’s:
- Training (responders + facility staff roles)
- SOP + signage + roof plan (reduces guesswork)
- Product availability where it matters (on-site for critical facilities, plus FD cache for broader coverage)
This is the difference between property protection and operational resilience.
If PV is on the roof, it’s part of the incident – whether it started the fire or not. Tools that reduce generation at the source can give Incident Command more options to stabilize the scene, protect responders, and return critical public buildings to service sooner. But the real win comes when the tool is placed correctly (on-site for high-occupancy facilities), paired with clear SOPs, and integrated into the fire service’s ICS playbook.
If PV is on the roof, the sites that win are the ones that remove guesswork and shorten the time to stabilization.
Case Scenario: Combiner Box Fire at a Shopping Mall (PV on Roof)
Setting: Midday, busy trading hours. A shopping mall has a large rooftop PV array feeding multiple inverters. Smoke is reported from the roof area. Security confirms a combiner box is involved.
What’s happening (in plain terms)
A combiner box fault can create intense localized heat, smoke, and potential flame. Even if the mall shuts down AC supplies, PV DC generation can still persist in daylight, and damaged conductors/connectors can create arc/shock hazards. Roof access and ventilation choices become complicated because PV is now part of the roof environment.
ICS Priorities Applied
1) Life Safety (first priority)
- Immediate actions: Evacuate affected zones (and consider full mall evacuation depending on smoke spread), account for staff/contractors, isolate public from roof access points.
- Establish hot/warm/cold zones and prevent untrained staff from “going to look.”
- Key PV safeguard: treat the roof and PV DC pathways as potentially energized—even if switches are off.
Stop point: If roof integrity is uncertain or arcing is visible/likely, crews do not commit onto the roof without controlled access and a clear plan.
2) Incident Stabilization (control fire + control energy)
- Incident Commander assigns: Roof Division (if required), Fire Attack/Exposure Group, and an Electrical Hazard function (technical specialist or qualified adviser).
- Secure what can be isolated: utility AC/main, inverter shutdown (with the understanding this does not guarantee a de-energized array).
- Defensive protection to prevent extension into roof voids, plant rooms, or internal shafts—especially where DC routes penetrate the building.
- PV-aware tactic: restrict cutting/ventilation to preplanned areas (or avoid roof cutting if PV layout is unknown).
Decision trigger: If the combiner fire is fed by an energized fault condition and safe access is limited, the strategy may shift to controlled defensive operations until the electrical hazard state is reduced.
3) Property Conservation (after stabilization)
- Protect exposures: adjacent arrays, inverter rooms, rooftop plant, and critical mall boards.
- Plan the handover: cordon roof zones, document what is damaged, and ensure PV O&M/electrical contractor attends before re-entry.
- Manage downtime: limit disruption to unaffected areas only once safety allows.
Outcomes under the three readiness models
A) PVSTOP on-site (mall-owned, immediately available)
- Operational advantage: faster access to a hazard-reduction option under IC direction.
- Can shorten the time from “active hazard” to “controlled state,” supporting safer overhaul and earlier controlled re-entry.
- Helps reduce the pressure to take risky roof actions while PV generation persists.
B) PVSTOP with Fire Department (dispatched resource)
- Useful, but arrival time matters. Early incident decisions may already have gone defensive.
- Still valuable for stabilization/overhaul, especially if the incident drags on or re-ignition risk persists.
C) No PVSTOP
- Stabilization relies more on exclusion zones, conservative tactics, and waiting for daylight conditions/technical isolation confirmation.
- Likely larger cordons, longer roof restrictions, and potentially longer business interruption.
“Lessons learned” box (what the mall should have in place)
- A PV emergency pack: roof layout, DC routes, inverter/combiner locations, and 24/7 O&M contacts.
- Preplanned roof access paths.
- A simple ICS-aligned SOP: who does what, when and under whose authority, plus handover steps to keep the roof safe after crews leave.
