Open void

The design of the ventilation system must provide this volume of air flow to provide sufficient dilution of the gas emissions. This applies to open void or void former systems. 

The required fresh air flow rate determined using the equation from CIRIA 149 can be substituted in the equations from BS 5925 1991 to determine the necessary ventilation area. Alternatively a pumping system can be sized to give this air flow. Box 8.5 gives an example of the use of the equations from BS 5925. 

Allow for the design wind speed being exceeded 80% of the time (i.e. this is the worst case value and gives the highest confidence that the passive system will operate) and consider an exposed coastal location So factor = 0.56 

Determine factors K and a from Table 8 in BS 5925 1991 to allow for height of vent and nature of surrounding terrain. 

Therefore, from BS 5925 1991 the reference wind speed is u = u x Kx zf (where 2 = height of vent) 

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Ligands with other substituents in position 2 of the pyrimidine or the triazine rings have been designed to orientate these functions towards the inside of the open void created in the grids, with the aim of favoring their interactions with the hosted anions. 

However, the processes are mainly controlled by the microstructures on the alloy substrate including such features as dislocations, grain boundaries, and open voids in the alloy substrates. 

Figure 52-9 Sloppy, unacceptable brickwork with open voids. There is insufficient mortar in the bed joint, and the bottom of the brick are not fully covered.

Lattice pattern It is a pattern with a fixed arrangement of open voids. 

Lattice pattern In filament winding, a pattern with a fixed arrangement of open voids producing a basket-weave effect. Rhodes G (1999) Crystallography made crystal clear a guide for users of macromolecular models. Elsevier Science and Technology Books, New York. 

BG-sign. A sign that the slip resistance of a surface has been tested by the Berufsgenossenschaftliche Institut fiir Arbeitssicherheit. The sign is accompanied by a classification of the open voids and the slip resistance. 

An open void below a pre-cast suspended slab... 

The Partners in Technology report indicated that polystyrene shuttering is almost as effective as an open void of similar depth. The effectiveness is, as would be expected, sensitive to the actual venting provided. The modelling demonstrated that the polystyrene systems can be designed to vent below 30 m... 

Passive ventilation performance can be estimated using simple calculations. The most commonly adopted approach is described and examples are given for open voids and air flow through a void former. 

Monitoring in subfloor voids should preferably be carried out via specially installed monitoring points. In open voids these can be retrofitted by drilling through walls and installing small diameter tubes to the centre of the void. 

Trench walls tend to collapse easily under various geological and morphological conditions. Fault zones easily reduce the cohesion of the material by crushing and creating open voids. High water table can evoke the collapse of unconsolidated... 

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