The beauty of using a small compressor is that the hydrogen has a chance to cool down to ambient temperatures in the pressure vessel. Room temperature fusion can then take place when the pressure has built up enough. A word of warning though!
"Don't touch that!"
Once the pressure is approaching the critical point when fusion is about to take place, keep children away from the apparatus. They won't understand that the slightest knock could trigger a chain reaction. Small children, babies and pets don`t even know what thermonuclear catastrophe means. Be careful out there.