Okay, usually the term "apartment" is used when you don't have control of the property and have restrictions on what you can do...
Well then, you can put the CO2 or N2 Dewar (or both) on the driveway side first floor or basement, and pop a fill port in the wall. If you have a basement Bilco Door you can get them down there easily. And add extra ventilation in the room with the laser.
Now realize that you may get impetus to repave the driveway, most of them aren't built for a 14K to 20K truck to back up them once a week. But that's a whole lot better than swapping out big welding size bottles every week.
Leave the upstairs untainted by Work Stuff, and put all the dirty things down in the basement. Oh, and be sure to drywall the basement ceiling, and make sure the door to upstairs is a solid core 2-Hour rated - that's your firebreak. Even if you've got lumps and steps in the ceiling for pipes and ductwork, you want to slow it down enough the firemen can get it out before you've got a bunch of burned joists and structural damage to replace.