The units come in battery and electric.  The battery unit covers 200 to 400 square feet and the electric covers 600 to 800 square feet. In our experience the best place to put the unit is near the front door. This provides optimum effect for your guests. Try to keep the unit away from your return A/C vent. Over time you will get accustomed to the fragrance and it will seem lighter than it actually is. As with any perfume type product, keep up and away from children and pets. It's a good idea to refill over the sink in case of spills. Changing the wicks every 2 to 4 weeks keeps the system working at its best. As you can see in the picture, the more wicks the stronger the fragrance level.One small wick would be a light scent level and 3 wicks would be strong. Each quart of fragrance has wicks attached to it with a rubber band. With each quart we enclose a squirt-lid that makes it easy to fill your fragrance cup. When using squares, remove fragrance cup and place a square upright in bottom of unit as shown. The unit will hold 4 squares. After about a month place another square beside the 1st one. Then after another month add a 3rd square and a 4th after 4 months. On the 5th month remove the 1st and keep rotating. Do not put squares on any surface(countertop,dash,desktop,etc) as they are saturated with fragrance. Every few months its a good idea to clean the air freshener motor of dust and spray with any silicone or WD-40 type lube. As shown in the picture there are 4 lube points. Unplug the air freshener and take it outside and spray into the 4 lube points. Let it dry and wipe off excess before plugging back in. This applies to the older units, not the new units which are a sealed computer fan. They are very quiet and reliable but very delicate fan blades break easily and should not be touched. Lube points