Most air purifiers have a maximum coverage area listed in square feet, so you can compare to your calculations to find an air purifier that is the best fit for your home. If you have an open floor plan or high ceilings, opt for an air purifier that has more coverage. A whisper is around 30 decibels, so expect air purifiers in this noise range to be almost virtually silent. Since air purifier filters are designed to collect and trap different size particles and contaminants, they can get gunky pretty easily. If you’re easily overstimulated by loud noises, consider an air purifier that has different modes so you can adjust the speed of the internal fan.