Joint Sealer

I inspected this house yesterday, the HVAC ducts appear to be sealed with an asphalt cement instead of mastic, the ducts do not appear to be leaking.

Question, is asphalt cement an acceptable duct sealant?

Yes it is commonly used in the west where the ducting is exposed to the weather, once dried the “smell” disappears, just looks poor and is more costly then mastic on indoor installations. May not pass code

Thanks John.