Book - School of Science and Technology

Methods of ventilation 359other, inlets may connect to a rising shaft with, perhaps, some form of heater at the base.Subject to decision by the fire authority, it may be possible to use the shaft provided forrising water pipes for ductwork but not, of course, if space be allocated also to wastesfrom sanitary fittings. Some authorities require that a lobby be introduced at the entranceto toilets in public buildings and that this be provided with a supply of outside air by aninlet plant serving no other duty.Mechanical inlet and natural extractThis proposition should not be confused with the plenum heating system described inChapter 6. It is typified, for application to an office building, by the arrangement shownin Figure 13.13. As may be seen, an air supply from some central source is ducted througha corridor ceiling void to individual rooms; the vitiated air escapes therefrom, through alowlevel register, to the corridor proper and thence to outside. It is nowunlikely that afire authority would permit the construction of such a system since it has the potential toendanger the atmosphere of an escape route. A single room, perhaps an office, might havean outside air supply from some form of reversible fan unit as described earlier but thishardly falls within the context of the present heading.For an industrial application, such a system might consist of a number of individualunit heaters, each with an outside air inlet as described in Chapter 8, and working inparallel with natural roof ventilators. But this arrangement is barely a credible propositionfor present-day requirements.The ventilation of boiler houses is a special case as a result of the air consumedin combustion. The volume required may be estimated, as was described in Chapter 12(p. 336), and, where the boiler house is above ground, this quantity may be adequatewithout any augmentation. Where a boiler house is sited in a basement, or otherwiseremote from outside air, the amount of heat emitted by the plant may produce conditionswhich are unacceptable to maintenance staff and thus be the criterion for determinationof the ventilation air quantity. As a notional figure representing emission by a heatingInlet ductOfficeCorridorFigure 13.13 Mechanical inlet and natural extract