Smoke generators

Miscellaneous chemicals are used to modify the final properties of rigid polyurethane foams. Eor example, halogenated materials are used for flammabihty reduction, diols may be added for toughness or flexibiUty, and terephthalate-based polyester polyols may be used for decreased flammabiUty and smoke generation. Measurements of flammabihty and smoke characteristics are made with laboratory tests and do not necessarily reflect the effects of foams in actual fire situations. 

Another valuable characteristic of many phosphazene polymers is their flame-retardant behavior and low smoke generation on combustion (13). This property is utilized in commercial appHcations. 

Flammability. PhenoHcs have inherently low flammabiHty and relatively low smoke generation. For this reason they are widely used in mass transit, tiinnel-building, and mining. Fiber glass-reinforced phenoHc composites are capable of attaining the 1990 U.S. Federal Aviation Administration (FAA) regulations for total heat release and peak heat release for aircraft interior facings (1,70). 

PhenoHc sheet-molding compound is seeing increased use in interior and exterior appHcations in mass transit. The trains in service on the English Channel tunnel have several panels made from phenoHc SMC which had to meet the strict European safety standards for fire and smoke generation. 

Smoke-Generating Devices. Smoke generators are used by the military for daytime obscuration and signaling. For field use where portable stable systems ate requited, pyrotechnic devices are often employed. The primary composition since the 1940s has been HC smoke, which generates a cloud of zinc chloride, ZnCl, smoke by a series of reactions between hexachloroethane, C2Clg(HC), zinc oxide, and aluminum (3) (eq. 4—6). The zinc regenerated in... 

Sanitary ware, including tubs, showers, combined units, basins, and toilet tank, may be made of thermoformed ABS or acryHc sheet, molded glass-fiber-reinforced polyester, or cast acryHc resins. The glass-polyester type dominates the tub/shower market. It is possible to install the units as a two-component system, assembled in place. Gel coats may be of thermoformed decorative acryHc skins. To reduce the smoke generated by fire, methyl... 

In addition to the inherent flame resistance, the polymers are also interesting because of the low smoke generation and low levels of toxic and corrosive emissions when exposed to fire. 

Good flame resistance, low smoke generation and good ablative characteristics. 

These materials are developed from the polyetherimides introduced by General Electric (see also Section 18.14.2). At the time of writing one grade, Ultem Siltem STM 1500, is being offered. It is of particular interest as a material for wire and cable insulation, as it not only has excellent flame resistance coupled with low smoke generation but also avoids possible toxic and corrosion hazards of halogenated polymers. This can be of importance where there are possible escape problems in the event of a fire, such as in tunnels, aircraft and marine (particularly submarine) vessels. 

Withdrawn) 1974 AMD 1 Laboratory methods of test for determination of smoke generation charactenstics of cellular plastics and cellular rubber materials. Part 1 Method for testing a 25 mm cube test specimen of low density material (up to 130 kg/metres cubed) to continuous flaming conditions (AMD 7688) dated 15 July 1993. Withdrawn, superseded by BS ISO 5659-2 1994... 

Withdrawn) 1974 AMD 1 Laboratory methods of test for determination of smoke generation charactenstics of cellular plastics and cellular rubber materials. Superseded by BS ISO 5659-2 1994... 

Another simple way fo evaluate the exhaust is to use smoke to visualize the air streamlines. It is also possible to see how far the exhaust readies by observing the smoke generated at different distances. This is best achieved by using the source (if it generates particles or warm gases) and a suitably placed lamp to illuminate the contaminants. 

Capture efficiency measurements may be used to evaluate the function of a canopy hood (see Section 10.5). Capture velocity is not a feasible evaluation tool, since a canopy hood does not generate an air velocity close to the source. It is also possible to use exposure measurements for workers outside the plume area. Since most hot processes generate visible contaminants, visual inspection of the flow, especially around hood edges, might provide a qualitative evaluation. Many contaminants could however be invisible when diluted and smoke generators (Section 10.5) may be necessary to find leakages (temporary or permanent) around the hood edges. 

The smoke generator shown in Fig. 12.3 allows the user to ad)ust the flow rate of the smoke and also to connect different types of spreaders throufdi 3 several-meter-Iong tube. This makes it possible to simulate different types of sources, such as a point source with low or high momentum, a line source, a surface source, or any other source with any geometry. Some examples are it-lusrrated in Fig. 12.4. 

An application of the smoke generation principle described above is the smoke wire." This simulates a line source and makes it possible to efteccively study the airflow patterns in a layer, which is often desirable. A thin steel wire is... 

Smoke extraction A mechanical ot natu-tal means by which smoke generated during a process or a fire is removed from the space to outdoors. 

Smoke generator A device that electri cally heats oil-producing smoke. The smoke is liberated from a nozzle by either thermal forces or by means of a fan and used to observe airflow patterns within a space or to observe leakage from ductwork, etc. 

Smoke tube A tube or a canister containing a smoke-generating chemical used to observe air movements within a room. 

Nebel, m. mist, fog, haze (loosely) smoke, -apparat, m. atomizer, sprayer MU.) smoke generator. 

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