Smoke, not heat, is what fills escape routes and cockpits, which is why the NBS chamber is a fixture of transport and building material testing. A specimen is exposed inside a sealed chamber to a radiant furnace (with pilot flames for flaming mode) and the smoke that accumulates is measured by a vertical light beam and photometer. The Motis SDB chamber has internal dimensions of 914 x 914 x 610 mm with Teflon-coated walls, a full-opening door and the photometric system the methods require.
How the NBS Smoke Density Chamber works
The chamber is sealed and the specimen is exposed horizontally to the radiant furnace at the irradiance set by the method - 25 kW/m² in the ASTM E662 furnace arrangement. Smoke accumulates in the closed volume and progressively attenuates the vertical light path; the photomultiplier-based optical system records transmittance, from which specific optical density is calculated over time, in both non-flaming and flaming modes.
Key specifications
| Standards | ASTM E662, ISO 5659-2, NES 711; BS 6401 listed for this chamber family |
|---|---|
| Chamber | Internal dimensions 914 x 914 x 610 mm; Teflon-coated inner and outer walls; full-opening door |
| Exposure | ASTM E662 radiant furnace, 25 kW/m² output; standard six-burner arrangement for flaming tests |
| Safety and pressure | Explosion-relief aluminium foil device; pressure-relief port with regulating vessel on the chamber top |
| Gas handling | Automatic cylinder-driven intake and exhaust at chamber top and bottom |
| Heat measurement | Foil-backed copper-disc calorimeter, water/air cooled, for surface temperature setting |
| Optical system | Photomultiplier tube sensor; options include Drager gas detection tubes for aviation smoke toxicity and an FTIR interface for qualitative and quantitative smoke gas analysis |
What the test reports
- Specific optical density Ds over time
- Maximum specific optical density (Dm)
- Smoke values at the time points the governing method requires (for example Ds at 1.5 and 4 minutes in aviation work)
Applications
Aviation (FAR 25.853 smoke requirements), railway (EN 45545-2 smoke density), marine and building materials laboratories run the NBS chamber as their primary smoke instrument. It pairs with the 3-metre cube for cable smoke work and with FTIR analysis where smoke toxicity must be quantified.
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.
Flaming or non-flaming - does the chamber do both?
Yes. The methods define both modes: radiant exposure alone (non-flaming/pyrolysis) and radiant exposure with pilot burners (flaming). The chamber, furnace and burner arrangement cover both.
Configuration, installation and support
Every NBS Smoke Density Chamber 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 E662, ISO 5659-2, NES 711, BS 6401. 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 NBS Smoke Density Chamber correctly the first time, send: the standard and edition you will test to (ASTM E662, ISO 5659-2, NES 711, BS 6401); 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.