Preventing the gas from filling the volume seems to be easier than trying to make the box explosion-proof. Just install a one-way valve into the money slot which will let the bills out but vent the gas outside. Alternatively, make a two-hatch, airlock-like slot.
The probable reason something similar isn't done yet is that banks look for some dirt cheap solution; it may actually be cheaper to lose money while this kind of attack is infrequent.
AVS Video Editor. It's not free (although $39 is pretty close to that) and may not be suitable for your needs you didn't give much details about, but as I was looking for a free video editing tool a couple of years ago, I couldn't find anything which would a) support AVCHD; b) play Full HD without dropping frames; c) not crash every five minutes;
In the recent decades we've been eyewitnesses to the revolutionary breakthroughs in such fields as energy, transportation, healthcare, and space industry, to name a few. The technologies emerged are nowadays pretty much ubiquitous and impossible to go without in day to day life. Yet the hardware IT industry is stuck with Moore's law and silicon, and there's even an embarrassing retreat to functional programming in the software branch.
We've to build robots (space dock, new type of engine, new rad hardening, etc) first - these myths have long been debunked by Robert Zubrin. It's the never-ending process of getting ready that the space industry earns the Benjamins from, not the flight itself.
I had been learning it about 20 years ago; developing ability to cherry-pick key words and to absorb the _rough_ meaning of the whole page in a couple of seconds was one of the keystones of the technique. They promised it won't hurt when reading fiction, but it actually turned into inability to enjoy the reading itself. On the other hand, it did help to digest tons of technical books, so I'm not complaining.