Brisker uses a gentle heating element to warm the interior temperature to ~120 degrees Fahrenheit. Warmer air spreads moisture out, so items inside the Brisker dry out and stay crunchy.
This all works because of the principles of relative humidity. With the air inside the Brisker about 40-50 degrees warmer than room temperature in your kitchen or pantry, humidity and moisture decreases inside of the Brisker relative to the humidity in your kitchen.
Here's a neat video explaining how relative humidity works.