Any CO2 Laser has a very limited operational temperature range. It can be pushed but at the shortened lifespan from burnout. Without AC if there is not a problem of overheating there is a bigger problem of death by cold as the coolant water freezes.
You could air-condition as small an area as a hydroponic grow tent or the whole garage, but unless you have a dry cave handy with electricity it will need some sort of temperature controlled environment,