If you can smell the wood burning, you're not getting a sufficiently clean burn. The post-2020-EPA-regulation landscape for wood burning appliances in the US at

If you can smell the wood burning, you're not getting a sufficiently clean burn. The post-2020-EPA-regulation landscape for wood burning appliances in the US at least are all significantly better than the older stoves. As for air quality, a rocket mass heater will get hot enough to put out zero CO, and most or all of the particulate will be broken down as well, but sadly there's only one device I know of that is UL-certified. They are very much a niche concept; most stoves and masonry heaters will be putting out some, and in a city there'll be enough that it'll have an effect on health.