North American building codes classify interior finishes by two numbers from this tunnel: the flame spread index and the smoke developed index, measured against red oak (100) and cement board (0) references. The specimen forms the ceiling of a tunnel roughly 7.6 metres long, exposed to gas burners at one end with a controlled draught. The Motis Steiner tunnel covers the ASTM E84 configuration, and the DI-registered ST-910 configuration covers the Steiner tunnel method of UL 910 / NFPA 262 used for plenum cables.
How the Steiner Tunnel (ASTM E84) works
The specimen is mounted as the tunnel ceiling and the burner flame is applied at the fire end under the standard air flow. Observers and instrumentation track the flame front along the tunnel over the 10-minute test, while a photometer in the exhaust measures smoke. The flame spread and smoke curves are converted into the two indices by comparison with the calibration materials.
Key specifications
| Standards | ASTM E84; Steiner tunnel configuration for UL 910 and NFPA 262 (model ST-910) for plenum cable testing |
|---|---|
| Specimen | Full tunnel-length specimen mounted as the ceiling of the tunnel (method dimensions per ASTM E84) |
| Test duration | 10 minutes (ASTM E84) |
| Outputs basis | Flame front progression and exhaust light absorption, indexed against red oak and inorganic cement board calibration |
What the test reports
- Flame spread index (FSI)
- Smoke developed index (SDI)
- Flame front distance versus time record
Applications
US-facing building product manufacturers and cable producers are the users: Class A/B/C interior finish classifications come from this tunnel, and plenum cable listings use the same tunnel principle. It is a dedicated installation and appears in most North American fire laboratory builds.
Frequently asked questions
Which standard should I order against?
Order against the standard your reports must cite. The instrument platform is shared across the listed standards, but fixtures, software templates and calibration routines differ, so name the standard (and its year) in your inquiry and the configuration will be matched to it.
Can the instrument be installed in an existing laboratory?
Yes, in most cases. Tell us the available floor space, ceiling height, exhaust capacity and gas supplies in your inquiry; large systems such as the SBI and tunnel furnaces need a dedicated exhaust arrangement, which is confirmed in the layout proposal before ordering.
How big is the installation?
The tunnel itself is about 7.6 m long plus burner, exhaust and observation arrangements. It is a room-planning item; send laboratory dimensions with your inquiry.
Configuration, installation and support
Every Steiner Tunnel (ASTM E84) is supplied as a configured system, not a bare instrument: the test chamber or frame, the burner or heater assemblies named in the method, the measurement chain and the control software with the report templates for ASTM E84, UL 910, NFPA 262. Before quotation we confirm the installation conditions with you - floor loading and ceiling height for large rigs, exhaust and extraction routes, gas and fuel services, and power supply - because a fire test instrument only produces defensible data when the room around it is right. Commissioning covers assembly, calibration of the measurement chain against the method's own checks, and training of your operators on running the test and maintaining the apparatus. Spare ignition parts, thermocouples and other consumables for the first period of operation can be included in the supply, and the instrument is supported with calibration and maintenance services after installation.
What to include in your inquiry
To quote the Steiner Tunnel (ASTM E84) correctly the first time, send: the standard and edition you will test to (ASTM E84, UL 910, NFPA 262); the materials or products you will test and their sizes; the configuration options you already know you need; and the destination laboratory's location and available services. If you are building a new fire laboratory rather than adding one instrument, say so - this apparatus is often planned together with the other instruments in its category, and a combined layout and exhaust plan is cheaper than three separate ones.