In homes with forced air heat there may be large cracks or gaps where the ducts pass through the ceilings, floors and walls. Caulk between the metal duct opening and the ceiling, floor or wall it is mounted to.
Shavings can pile up around a hole being drilled, making it hard for you to see what you are doing. To prevent this, push the point of the drill bit through a 4-in. strip of masking tape, then draw the tape up the bit so it will clear the work. Fold the strip lengthwise to bring the sticky sides together. The tape "wings" will act as a fan to clear the surface.