I’m not familiar with WWT, maybe WETT?
http://www.wettinc.ca/ I’m not aware of this certification is lower 48, I am familiar with CSIA http://www.csia.org/ NFPA and similar. Call a local and reputable Chimney Pro in your area and ask about credentials in your area!
When dealing with Fireplace inspections, I try to inform customers about my inspection and that Level 2 Inspections are encourage at transfer of sale for Wood/Fuel Burning Fireplaces
From Chimney Safety Institute of America
A Level 2 inspection is required when any changes are made to the system. Changes can include a change in the fuel type, changes to the shape of, or material in, the flue (i.e. relining), or the replacement or addition of an appliance of a dissimilar type, input rating or efficiency. Additionally, a Level 2 inspection is required **upon the sale or transfer of a property **or after an operation malfunction or external event that is likely to have caused damage to the chimney. Building fires, chimney fires, seismic events as well as weather events are all indicators that this level of inspection is warranted. A Level 2 inspection is a more in-depth inspection than a Level 1 inspection.– When a Level 1 or Level 2 inspection suggests a hidden hazard and the evaluation cannot be performed without special tools to access concealed areas of the chimney or flue, a Level 3 inspection is recommended. A Level 3 inspection addresses the proper construction and the condition of concealed portions of the chimney structure and the flue. Removal or destruction, as necessary, of permanently attached portions of the chimney or building structure will be required for the completion of a Level 3 inspection. A Level 2 inspection includes everything in a Level 1 inspection, plus the accessible portions of the chimney exterior and interior including attics, crawl spaces and basements. It will address proper clearances from combustibles in accessible locations.