Staged evacuation

FIGURE 14 Setup for second- and third-harmonic generation by means of Maker fringe technique. BS, beamsplitter F, 2.3. filters L, lens S, sample on a rotation stage (evacuable sample chamber especially for THG experiments) R, reference P, polarizer Ma.b, monochromators PM photomultiplier PA, amplifier PD, photodiode T, trigger entrance of the boxcar amplifier. (From Ref. 26.)... 

Total simultaneous evacuation - the most common way to achieve simultaneous evacuation is that upon the activation of a single call point or detector an instantaneous warning from all fire alarm sounders is given as the signal for an immediate evacuation. This is referred to as a single stage evacuation. 

However, even when it is considered to evacuate the whole building simultaneously there are occasions where an immediate wholesale, uncontrolled evacuation would present its own, significant risks. For example, in a theatre or other place of public entertainment it is important that an evacuation is achieved without creating panic among the audience who may be seated in dark unfamiliar surroundings. In this case and in some other circumstances it will appropriate to adopt a two-staged evacuation. 

In a two-staged evacuation, there is an investigation period before the fire alarm sounders are activated. This approach is adopted for facilities such as halls of residence (student accommodation) and places of public entertainment. A staged evacuation ensures that confirmation of a fire can be verified prior to running the risk of... 

After passing through several stages of processing, gas pressure may need to be increased before it can be evacuated, used for gas lift or re-injected. Inter-stage pressure increases may also be required for further processing, particularly where wellhead pressure is low. Gas is compressed to increase its pressure. 

As a first stage, the stream of liquid from an HPLC eluant is passed through a narrow tube toward the LINC interface. Near the end of the tube, the liquid stream is injected with helium gas so that it leaves the end of the tube as a high-velocity spray of small drops of liquid mixed with helium. From there, the mixture enters an evacuation chamber (Figure 12.1). The formation of spray (nebulizing) is very similar to that occurring in the action of aerosol spray cans (see Chapter 19). 

If this approximate evacuation period is too long, it may be shortened by adding a larger last stage to the ejector or by adding a noncondensing ejector in parallel... 

Prior to an anticipated air release of a hazardous material, a circular evacuation strategy may be appropriate. Evacuation might also be initiated for a keyhole-shaped area baised on prevailing wind conditions. These strategies are illustrated below. When a large number of people aie involved, the evacuation should be staged, that is, arc ls closest to the site should be evacuated first and the evacuation zone gradually expanded. 

Figures 6-26A and B give q pical good estimating selection curves for single-stage ejectors. Table 6-9 gives evacuation factors.

Example 6-10 Size Selection. Utilities and Evacuation Time for Single Stage Ejector... 

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