NFPA 30 advises that if you must vent a Safety Cabinet to the outside, it must be in a manner that does not compromise the safety performance of the Safety Cabinet.
It is recognized that may require storage cabinets to be vented. Safety cabinets should be vented from the lower vent opening with make-up air supplied to the upper vent opening. Mechanical exhaust ventilation is preferred.
In such cases, the ventilation system should be installed so as not to reduce the fire protection capabilities of the safety cabinet during a fire. Means of accomplishing this may include thermally actuated dampers on the vent openings or proper insulation of the vent piping system. Manifold the vents of multiple storage cabinets should be avoided. Any make-up air to the cabinet should also be arranged in a similar manner. Remember, the intent of a flammable storage cabinet is to keep the contents of the cabinet away from the fire. The ductwork of the cabinet should have the same intent.