SPECIFICATIONS 



fourth square foot for clean machine shops and similar build- 

 ings ; of not less than one square foot for dirty machine shops ; 

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

 six square feet for forge shops, foundries and smelters. 



55. Openings in ventilators shall be provided with shut- 

 ters, sash, or louvres, or may be left open as specified. 



Shutters must be provided with a satisfactory device for 

 opening and closing. 



Louvres must be designed to prevent the blowing in of 

 rain and snow, and must be made stiff so that no appreciable 

 sagging will occur. They shall be made of not less than No. 

 20 gage galvanized steel for flat louvres and No. 24 gage gal- 

 vanized steel for corrugated louvres. 



56. Circular ventilators when used must be designed so 

 as to prevent down drafts. Net opening only shall be used in 

 calculations. 



57. Windows shall be provided in the exterior walls equal 

 to not less than 10 per cent of the entire exterior surface in 

 mill buildings, and of not less than 25 per cent in machine 

 shops, factories and similar buildings. 



Window glass up to 12" x 14" may be single strength, over 

 12" x 14" the glass shall be double strength. Window glass 

 shall be A grade except in smelters, foundries, forge shops, and 

 similar structures where it may be B grade. The sash and 

 frames shall be constructed of white pine. 



58. At least half of the lighting shall preferably be by 

 means of skylights, or sash in the sides of ventilators. 



Skylights shall be glazed with wire glass, or wire netting 

 shall be stretched beneath the skylights to prevent th -i broken 

 glass from falling into the building. Where there is danger of the 

 skylight glass being broken by objects falling on it, a wire 

 netting guard shall be provided on the outside. 



Skylight glass shall be carefully set, special care being 

 used to prevent leakage. Leakage and condensation on the in- 

 ner surface of the glass shall be carried to the down-spouts, or 

 outside the building by condensation gutters. 



59. Windows in sides of buildings shall be made with 

 counterbalanced sash, and in ventilators shall be made with 

 sliding or swing sash. 



Shutters and 

 Louvres. 



Circular Ventilatora 



Windows. 



Skylights. 



