It's hard to keep air bubbles out of sheet vinyl flooring. They pop up and stand out. Here's the quick fix: use a utility knife to make a slit along the length of the buble in an inconspiciuos place, such as dark lines in the floor's pattern. Use a pottery knife to spread the thin layer of vinyl floor adhesive under the bubble on both sides of the slit. Push up and down on the bubble to distribute the glue as widely as possible. Wipe up any excess glue and place a heavy object on the area to flatten it. Leave the weight in place overnight. The glue should be dry and the bubble should be gone by morning.