a friend of mine is selling a bunch of equipment and that includes the regular wood pallets that are used in warehouses
Your husband is right, untreated lumber is just cut wood. However since the variety and dryness and demension of the wood determines the efectiveness of it as a source of heating, burning pallet wood for anyone without an abundant suppply of it would be simply as ameans of disposal, not as a primary source of heat generation
Mixing pallet wood with logs makes a good hot fire. Most pallets are made of hardwood (usually oak). Should not be dangerous at all.
They may be burning hot because they're dry, small pieces with edges - they burn faster. If it's an evergreen wood (like pine, spruce, fir), you shouldn't burn it because the burning volatile oils in the wood coat the chimney and present a great fire hazard as it gets coated. These evergreen types of wood also tend to burn fast and hot because of these oils/sap, which are aromatic - they smell, but usually they smell nice, just possibly strong.
Pallets are made of whatever is available unless the customer specifies a particular wood species. You probably won't have access to these pallets as they are cycled with the loads they carry from and back to the original user. All that aside, most pallets are made from oak or gum. Both woods burn quite well although gum has a lot of gummy resins that might clog your chimney if allowed to burn at a smoulder. This doesn't seem to be your problem. Pallet wood is cut to minimum dimensions to support loads without adding weight for shipping. Because of these small dimensions and the structure of pallets, the wood dries very quickly and thoroughly which makes it burn rapidly and therefore create a lot of heat for a short time You should probably mix some split log-wood with the pallet wood. This will slow down the burning process and give ayou a more even heat over a longer period of time. Also, use you damper to restrict the air flow through the wood burner.
