Case 2. (For all sections of the class.) For the same internal generation rates as in C: earthquake causes serious damage to the air handlers, HEPA filter grid, and exhaust. conditions are as follows: . Final filter flow rate = 75 cfm/ column e Exhaust flow rate = 110 cfm e Make- up filter efficiency = 60% e Recirc filter efficiency = 95% e Final filter efficiency = 99.5% e External particle density = 2.5 x 106/ft3