At a national level in New Zealand there is no requirement for a retrofit to be approved. Just go ahead and install it to get the benefits. Ask if you are uncertain about your country.
There are clean air bylaws around New Zealand, and the world, that are unclear about retrofits because there has never been an invention like the IntensiFire. The IntensiFire will in general help these councils lower air pollution from your old woodstove. If used as instructed there will be little to no visible smoke from the IntensiFire, and looking for smoke is the way any enforcement is done.