Smoke tests

One particularly widely used test is the National Bureau of Standards (NBS) smoke chamber test. This provides a measure of the obscuration of visible light by smoke in units of specific optical density. The NBS smoke test can be run in either of two modes ... 

The flow should move smoothly into the cupboard and should not re emerge into the laboratory. It should be remembered that the smoke test is a negative test, i.e., if smoke is seen to emerge from the cupboard, the cupboard does leak if no smoke is seen to emerge, the cupboard may leak. 

The initial performance test for all local ventilation systems is a smoke test, which provides easy airflow visualization between the source and the hood, it helps to identify, with little effort, the main features of airflow patterns. Such a test, recorded by a video camera, allows performance comparisons to be made before and after improvements. Real contaminant or tracer gas measurements are necessary in the case of more detailed testing. 

The capture velocity of a hood is defined as the air velocity created by the hood at the point of contaminant generation. The hood must generate a capture velocity sufficient to overcome opposing air currents and transport the contaminant to the hood. For enclosing hoods, capture velocity is the velocity at the hood opening. In this case, the velocity must be sufficient to keep the contaminant in the hood. In practice, hood shape and the influence of crossdrafts on the measured capture velocity have to be considered. All three velocity components should be measured and used to calculate the magnitude and direction of the total velocity. Other methods used, not as good as the previous one, are to measure the velocity with a directional velocity sensor towards the hood or to measure the net velocity by an omnidirectional velocity sensor. In the last method the main airflow direction should be viewed and evaluated by means of a smoke test (see Sections 10.2.1 and 10.2.2.1). 

Modem electronic replacements for the Orsat apparatus include equipment manufactured in the United States by Bacharach, Inc. (www.bacharach-inc.com). This company produces handheld and boxed instruments that can be employed as comprehensive combustion and environmental analyzers, gas burner combustion testers, single gas analyzers, draft gauges, smoke test sets, sling psychrometers, and the like. 

Fig. 10. NBS Smoke Test of Flexible PVC Containing Alumina Trihydrate. ZB - Zinc Borate.

Fig. 11. NBS Smoke Test of Ethylene-Vinyl Acetate. ZB -Zinc Borate, ATH - Alumina Trihydrate.

During the 1970 s and early 1980 s a large number of test methods were developed to measure the toxic potency of the smoke produced from burning materials. The ones most widely used are in refs. 29-32. These tests differ in several respects the conditions under which the material is burnt, the characteristics of the air flow (i.e. static or dynamic), the type of method used to evaluate smoke toxicity (i.e. analytical or bioassay), the animal model used for bioassay tests, and the end point determined. As a consequence of all these differences the tests result in a tremendous variation of ranking for the smoke of various materials. A case in point was made in a study of the toxic potency of 14 materials by two methods [33]. It showed (Table I) that the material ranked most toxic by one of the protocols used was ranked least toxic by the other protocol Although neither of these protocols is in common use in the late 1980 s, it illustrates some of the shortcomings associated with small scale toxic potency of smoke tests. 

The location of the smoke detectors should be based on an engineering survey of the area to be protected. Factors such as air flow, proximity to airhandling system diffusers and other physical features of the installation need to be taken into account. Smoke tests can be run to verify that the air flow within the protected area favors the smoke detectors. 

Ballantyne et al. examined the ocular effects of CS in polyethylene glycol-CPEG) solutions, as a powder, and as smokes. Test solutions were made up in concentrations of 0.5, 1, 2, 5, and 10Z CS in PEG. Each was tested on 10 rabbits with 0.1-ml drops instilled into one eye. Four groups of 20 rabbits were tested at 0.5, 1, 2, and 5 mg of CS as a powder. Ten rabbits were exposed to CS grenade smoke for 15 min the average CS concentration was 6 g/m3. The effects of the hydrolysis products of CS were also examined. Ten animals were tested with o-chlorobenzaldehyde and 10 with malono-nitrile. The amounts of the two compounds were determined as the ratio obtained by the hydrolysis of a 5Z solution of CS. This was a... 

Checks to be performed as a prerequisite air velocity. Smoke test study for dead end (if any) or air sweeping efficiency should also be reviewed in concluding the studies for critical points for routine monitoring. 

During a turnaround, a smoke test should be carried out as follows ... 

Busch, A. M., Correlation of Laboratory Smoke Test with Carbon Deposition in... 

FIGURE 9.5 Smoke test of flexible PVC (ASTM E-662, all formulations contain ATH, ZB-Firebrake ZB). 

Components3 (phr) ASTM E-662 Smoke Test (Dmc) Limiting Oxygen Index (%)... 

Chapter 6 Smoke test. The test is based on the National Bureau of Standards (NBS, now NIST, National Institute of Standards and Technology) smoke density chamber, which has also been standardized as ASTM E 66239 (see also Section 4.1.1). The test exposes a vertical test specimen ca. 75 mm x 75 mm (3 in. x 3 in.) to an incident radiant heat flux of 25kW/m2, from a radiant heat burner for 4 min, in the presence of an open-flame pilot burner. The test applies to the same materials as the heat release rate test. The acceptance criterion is an average maximum specific optical density of smoke that does not exceed 200 (no units). 

The laminate construction in FRP parts can have an effect on flame spread and smoke test results. A study was conducted by Stevens15 and published in the proceedings of Composites 2007 conference. This study looked at how glass fiber content and panel thickness affected the ASTM E-84 flame spread index (FSI) and smoke developed index (SDI). The effects of fiber content and thickness on cone calorimeter results were also evaluated. Another study was conducted by Dempsey16 looking at the effect of glass content in several fire tests, and in this paper, he also found a correlation between the FR performance and glass content. 

Containment leakage (To verify absence of cross-contamination) All classes 24 months Demonstrate that contaminant is maintained within a room by means of airflow direction smoke tests room air pressures. In accordance with ISO 14644-3 Annex B4 ... 

Airflow visualization (To verify required airflow patterns) All classes 24 months Tests to demonstrate airflows from clean to dirty areas do not cause cross-contamination uniformly from laminar flow units. Demonstrated by actual or videotaped smoke tests. In accordance with ISO 14644-3 Annex B7 ... 

Simulate process with media (not freeze) Smoke test (transport area)... 

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