The two forms differ somewhat in their treatment of this loss. First, the DP-3. Of the exclusions you cite, 2.h.(1) wear and tear, may be applicable since this loss has occurred over time, and that is what this series of exclusions (2.h.) refers to. Exclusion 2.h.(2) mechanical breakdown seems less applicable since nothing mechanical broke down, and there was no inherent vice or latent defect. (Latent defect means a quality in the item that causes it to destroy itself, which did not happen in this case.)

The exclusion for pollutants appears more likely to preclude coverage, and it is interesting to note that this form does not give back coverage for pollution caused by any of the coverage C named perils, as does the homeowners form.

However, smoke is a by-product of fire, which is a covered cause of loss. Each time the woodburner was fired, smoke resulted. Although smoke is listed as a pollutant, smoke from industrial operations is clearly excluded in exclusion 2.h.(4). It might therefore be argued that the policy drafters intended to exclude this type of continuous smoke, but not the smoke that escapes when a home is heated or catches on fire.

Ultimately, the question might be one for a court of law to determine.

The HO 00 03 language makes it easier to argue for coverage. For one, as noted above, escape of pollutants is covered if caused by one of the coverage C named perils. The peril of smoke states that this means "sudden and accidental damage from smoke." Accidental the damage certainly was, but was it sudden? According to Webster's Collegiate Dictionary (Tenth Edition), the first meaning of sudden is "happening or coming unexpectedly." The third meaning is "marked by or manifesting abruptness or haste."

Under this peril, then, if a woodburner was fired up for the first or second time a case might be made for the smoke's being both abrupt and unexpected, but after that the insureds might have a difficult time arguing for coverage.  The insurer could reply that this was an on-going maintenance problem, and the insured did not preserve the property following a loss (a loss settlement condition) and therefore coverage would be precluded. (This would be true under the DP-3 policy as well.)

An interesting footnote: the 2000 HO 00 03 states that the smoke peril "means sudden and accidental damage from smoke, including the emission or puffback of smoke, soot, fumes or vapors from a boiler, furnace or related equipment" (emphasis added). Under this peril, the woodburner might be viewed as equipment that is related to a boiler or furnace by virtue of its ability to provide heat, rather than as, say, a humidifier attached to the furnace is related equipment.