Portable units do work, but a built-in system is better. Air purification systems can be retrofitted to hook up to your furnace and you don’t need an air conditioner. Furthermore, you don’t have to run the furnace to get the purification system to work. All you have to do is turn the fan on. By the way, running the fan doesn’t use nearly the amount of energy that running an air conditioner or heater would use. If you live in an area with heavy sand or smog, or if you have severe allergies a built-in system is a must. Keep in mind that if you’re looking to purify a small area a one-room purifier might work. Another alternative is a built-in ERV – Energy Recover Ventilator – system. An ERV brings in outdoor air at programmed intervals, and runs through the purifier and into the home. Low cost air cleaning and ventilation. Try it – you’ll like it!