I ran a number of 5830s out of the garage over the summer and asides from a thick layer of pollen and a few mangled bugs everything was fine. If I were to do it again though I'd duct the rigs with cardboard and use some box fans w/ chopped up furnace/AC air filters to filter the air a bit. Will have to find a similar solution for this upcoming summer as the rigs migrate outside the house again.
No offense, but there are good reasons to not do 24/7 unattended electrical operations with flammable materials.
While I've been known (in my much younger past) to run a machine in a static wrap bag (to decrease cat hairs) in a cardboard tray, I would not attempt to run my mining gear this way. I thought it was dangerous to make that PC work that way - 24/7 equipment that runs at full tilt boogie can experience unexpected events. I have responded to alarms on gear that turned out later to have melted, or caught fire in the switchroom/datacenter.
I appreciate your concern but perhaps I should have been a bit more clear in my plans. I have a wood/steel shelving unit that I will be shrouding the sides in cardboard and placing a box fan at the entrance of this wind tunnel. I've abused enough hardware competitively overclocking over the last half decade to see how fets fail and occasionally roast. Caps no longer explode and proper power supplies have OVP/OCP/short protection(that I have frequently tested due to MB/GPU fets exploding). I have greater concerns over GPUs dying and taking out a rig than a fet shorting to ground and potentially causing a short lived burst of flame.
This is the simplest solution to venting around 7 kW of heat outdoors. Contain and vent rather than vent an entire building.