Today upright vacuum cleaners are the most popular variety; outselling canister models 5 to 1. But both have drawbacks for some people. If you're allergic to dust or need quiet in your home, a built-in central vacuum system might be the answer. They're powerful, deep-cleaning and leave indoor air virtually dust-free. And, they're so quiet others can sleep while you clean. Installing one yourself is an easy project. The typical home needs only a few outlets, connected by ordinary PVC pipe, just glued together. Then, when you plug in the hose, the system starts and super-quiet, space-age housecleaning begins. There are many nifty gadgets available too, like a dust sensor that shuts it off when everything's clean or a high-tech dustpan. Just sweep dust and dirt into it with a broom, and it's gone. For maximum quiet, put the power unit in the garage or basement; for the cleanest air, vent unit exhaust outdoors, then breathe easy and let others sleep peacefully. And that's the On The House tip for today.