Hi, I wanted to enclose a FIO with Xbee in a small Bell Jar (vacuum chamber) and take temperature readings as the pressure drops. I was curious if there is any risk of damaging the electronics on board.
I doubt it. What would explode at only 1 atm?
I've had my Uno down to about 350 millibars absolute and it seemed quite happy.
You may get a bit of Copper Vacuumate develop on the tracks but this will be easily cleaned up afterwards with a liberal application of atmosphere.
The main risk is overheating due to lack of convection. If you circuit does not get hot in open air it is unlikely to get too hot in a vacuum.