A Chattanooga van builder burned through its roof. The hazard was on the floor

CHATTANOOGA, Tenn.

Chattanooga Fire Department companies were dispatched at 4:38 a.m. Eastern to 2311 East 23rd Street, the headquarters and fabrication floor of Site Seven Campers, a regional builder of custom off-road camper vans. First-arriving apparatus reported heavy fire in the industrial floor area with flames venting through the roof, as reported by Local 3 News and News Channel 9.

Incident command ran two attacks at once. An aerial platform put a master stream down onto the compromised roofline from outside while handline crews forced entry at the fabrication floor and pushed to the seat of the fire from inside. The building was unoccupied. The main body of fire was knocked down within about an hour, and the structural footprint held. Nobody was injured. The fire investigation bureau is still working the cause.

Upfitting is a solvent business wearing a workshop's clothes

A van conversion shop looks like a fabrication floor and behaves like a chemical plant. Adhesives and contact cements, fiberglass resin and catalysts, aerosol products, panel foams, upholstery solvents and paint materials all sit within a few metres of cutting, welding and grinding. NFPA 33 governs spray application of flammable materials and sets the ventilation and separation requirements that keep those operations from charging the air. NFPA 30B addresses aerosol products, which are stored and used in these shops in quantities nobody counts.

The newer hazard is the product itself. Modern overland builds carry substantial lithium-ion battery banks and dense wiring harnesses. A thermal runaway in a cell does not need oxygen, does not respond to a clean agent in the way a solvent fire does, and produces hydrogen fluoride among other products. Suppression design for a battery storage area is a different problem from suppression design for a spray booth, and both are different from a general warehouse wet system.

Open span roofs fail from above

An industrial building of this type is a wide, open volume under unprotected steel bar joists. Once flame impinges on unexposed structural steel, the assembly loses capacity in minutes rather than hours, and the roof becomes the first thing to surprise the incident commander. That is precisely why the Chattanooga crews opened the roof with a master stream before committing interior lines, and why the sequence in the department's account reads the way it does.

Early detection buys the minutes. A monitored sprinkler system designed under NFPA 13 with coverage suited to the actual fuel load, plus thermal imaging on the production floor and gas detection in solvent storage, moves the alarm from the fire department's arrival to the moment of ignition.

The audit a plant manager can start on Monday

Confirm what is stored, not what the permit says is stored. Verify that spray operations occur in a booth or area with the ventilation NFPA 33 requires and that filters and ductwork are cleaned on a schedule. Check that battery packs and cells under test are separated from combustible packaging, and that charging areas are monitored when the building is empty. Confirm that the fire alarm transmits to a supervising station rather than sounding only in a vacant building.

Then confirm the human layer. At 4:38 a.m. nobody was on site. A facility of that hazard profile benefits from a response that exists before the fire does.

The USPA position

USPA Nationwide Security delivers industrial security that includes thermal and visual patrols of production floors, solvent lockers and battery storage, with alarm response routed through the company's national operations centre. Where a suppression or detection system is impaired, the company deploys fire watch crews to hold a continuous manual detection loop over the affected zones until the system is returned to service.

The building held. The contents are another matter, and that is where the next few weeks of that investigation will go.