An ozone machine is a specialized device for clearing organic residues, such as infiltrated smoke particles and some sources of organic odors.
First, Ozone is a toxin. You do not want to inhale it, and certainly not in the quantities when in use. The better units have a timer device that permits unattended shutdown after a specified run time, so as to allow the ozone to dissipate before the technician re-enters to assess the progress.
The noise of an ozone unit is not much more than the sound of the internal air mover that pushes out the ozone from the exhaust port. The noise is just that of a small fan.
The smell of ozone is liken to the odor that emanates from an unsealed brushed electric motor. Take a whiff at the vents on an electric drill motor after it has run, if you have a real need to know what it smells like. The main difference is, that on an ozone machine the output is so high that your lungs would actually experience a burning.
The downside of an ozone machine is the inflated expectations people sometimes have. Some have tried it on situations where gross filth has not been removed, and they expect the ozone machine to work some kind of magic.
The device works phenomenally on select trace residues of organics, where chemical means is otherwise impractical. Ozone leave no residue of its own, and is very clean. However, ozone is completely incompatible with certain materials. First, is live anything. Ozone kills. You can't have pets, people, plants present during application. Second is leather. Ozone will severly age and harden leather. Third is rubber and certain plastics, to a much lesser extent.