2& B'EJLLETEK' 801;, U. S. DEPAETMEISTT OF AGRICULTUEE. 



The size of the door should be no greater than neeessary and in no 

 case should it exceed 120 square feet in area of opening or 12 feet in 

 width. It is preferable that the door opening be not wider than 10 

 feet.. Doors of large size are not nearly as strong in their resistance 

 to fire as smaller doors. Generally a door should be used on both 

 sides of the wall so as to protect the opening against a long-sustained 

 fire; this also gives greater certainty that at least one of the doors 

 will close. I 



It is extremely important that a door which has closed from any 

 cause be easy to open from either side^ as this is- a. matter of protee- | 

 tion to both life and property. If a door closes during a fire a person 

 may be confined in the fire area, or,, on the other hand, persons desir- 

 ing access to the &£& in order to extinguish it may be delayed by 

 tlieir effort to open the door.^ 



always tlie more satisfactory provided the purchase is confined to doors ap- 

 proved by tlie Underwriters' Laboratories. Insurance associations will furnish 

 detailed specifications and explanatory drawings showing the construction of 

 tin-clad doors, but, all too often, these are not followed by the mechanics. 



The istallation of all types of fire doors should be such as to insure- the hoM" 

 ing of the door very securly against the wall and so the hardw^are (including 

 the track for sliding door) should be extremely heavy and securely applied, 

 since it may be exposed to a long-continued fire. Pieces of hardware attached 

 to doors should be fastened with bolts or rivets extending entirely through the 

 door, while parts applied to the wall should be bolted entirely through it. 

 The door should overlap the wall 4 inches at both sides and top of the opening 

 unless it closes properly into a recessed steel frame securely anchored to the 

 wall. The joint formed at the floor should be close, the door closing upon a 

 steel or iron or concrete threshold extending under it 6 inches. 



"A variety of fire-door an-angements is shown by Plate XIV. Rolling steel 

 doors with various methods of installation are shown in figure 2, Drawing I. 

 "Detail A" shoAvs an economical method which is satisfactory in most cases. 



The sliding fire door is usually to be preferred, as its operation is easy and 

 positive. The usual installation, shown by figure 5^ provides an inclined track 

 (having a slope of three- fourths or 1 inch per foot), which causes the door to 

 roll shut by gravity when automatically freed from a restraining weight. 

 This weight (shown to the right of the door) is suspended by a cord which 

 passes over a pulley attached to the track or wall and thence to a bracket se- 

 cured to the side of the door and projected beyond it and into the opening. 

 The connection between this bracket and the cord is made by a " fusible link " 

 which consists of two thin pieces of metal soldered together with solder, which 

 melts at a temperature of 165° F. Tlie action in case of fire is that this 

 fusible link melts apart, thus disconnecting the restraining weight from the 

 door, Avhich rolls shut by its own weight acting iipon the inclineel track. The 

 fusible link should be projected into the opening in order that the natural 

 draft of heat througli the door may melt the fusible solder as soon as possible. 



In situations where the story height does not allow the necessary incline 

 for the track, it may be installed level and the closing action of the door 

 secured by an additional weight, as shown to the left of the opening in figure 

 3, Plate XIV. This second weight should be connected securely to the door 

 by a substantial sash chain in order that it may hold the door shut during a 



