Fig. 48a.—‘Sirocco’ Centrifugal Fan
Fig. 48b.—Showing exhaust aperture and fan blades
High-pressure fans are used mainly for technical purposes, as, for example, the driving of air or gas at high pressure. Localised ventilation is needed to limit diffusion of dust and fumes, which is attained in a measure also by separation of those workrooms in which persons come into contact with poisonous materials from others. Separation of workrooms, however, is not enough, as it is the individual who manipulates the poison for whom protection is desired. To enclose or hood over a dusty machine or fume-producing apparatus completely, or to close hermetically a whole series of operations by complicated technical arrangements, is only possible when no opening or hand feeding is required. Dangerous substances can only be wholly shut in by substitution of machinery for handwork.
Fig. 49.—Localised Exhaust Ventilation in a Colour Factory (Sturtevant Engineering Co., Ltd.)
| Fig. 50a. | Fig. 50b. |