CHAPTER XXIV. 

 VENTILATORS. 



Ventilation. Mill buildings are ventilated either by forced draft 

 or by natural ventilation. Natural ventilation is usually sufficient, al- 

 though forced ventilation is necessary in many factories and mills. The 

 problem of ventilation is too large to consider fully in this place and 

 the natural method of ventilation only will be discussed. The amount 

 of air required depends on the use to which the building is to be put ; 

 a common specification for the ventilation of mill buildings being that 

 ventilators shall be provided and located so as to ventilate the building 

 properly, and shall have a net opening for each 100 square feet of floor 

 space of not less than one-fourth square foot for clean machine shops 

 and similar buildings ; of not less than one square foot for dirty ma- 

 chine shops ; of not less than four square feet for mills ; and not less 

 than six square feet for forge shops, foundries and smelters. Ventila- 

 tors in high buildings are more effective than in low ones. The follow- 

 ing table will give an idea of the effect of height on ventilation.* 

 Height above ground. 20' 30' 40' 50' 



Machine shop, sq. ft. per 100 ^ ^ ^ y 2 round vents. 

 Mills, " " " " 7 6 5 4 Louvre vents. 



Forge shops, " " " " 9 8 7 6 Louvres or 



open vents. 



Monitor Ventilators. The openings in the clerestory of monitors 

 are fitted with louvres, shutters or sash, or may be left entirely open. 

 Louvres are made in many different ways, the Shiffler Louvres shown in 

 Fig. 158, and the Berlin Louvres shown in Fig. 159, are in common use. 

 The details of these louvres as made by various firms differ some- 

 what. 



*Mill Building Construction, H. G. Terrell. 



