So, just to be sure I understand both of you... You're telling me that at least some air movement is necessary for the device to reliably provide a steady hashrate, no matter what that is. Is that correct? Again, I have no problem letting it hashing at 10 GH/s, if that can mitigate the air trouble.
If you're going to run it without a fan, you'll need to upgrade the heatsink and thermal compound. The stock heatsink isn't good enough for just passive cooling
Upgrade it into what, if not a fan?