Dumb question re SFD sizing

[Yikes]

Question: If I have a duct that is 52"x16" (832 square inches net free area) and it passes through a fire rated wall that has a smoke/fire damper for the 52"x16" duct, is that smoke fire damper also equivalent to 832 square inches NFA? Or do the shutters inside the damper make the NFA smaller?

 

[Yankee Chronicler]

The shutters probably reduce the net free area. You need to examine the manufacturer's literature for the damper in question.

 

[Paul Sweet]

The free area reduction is minimal since the open blades are parallel to the air stream.