The thermo wood process burns resins and other extractives from the wood – the smell itself arises from chemical compounds called furfurals.
Tests have shown that there are no harmful emissions from thermally modified wood that is modified in an “open system” style kiln. While smell might not be appreciated by everyone, it is worth understanding that all wood has some form of odour – often referred to as volatile organic compounds (VOC’s).
Softwoods, particularly the pine species, have high level’s of VOC’s naturally and the open system thermal modification process (sometimes known as Thermowood) actually reduces VOC emissions.
The VOC’s of thermally modified softwoods are lower compared with those from their untreated counterparts because of the removal of large amounts of volatile terpenes during the heat treatment. In contrast, thermally modified hardwood total VOC emissions are increased compared with those from their untreated counterparts because they emit VOCs formed during wood degradation process created at high temperatures.
This article helps to explains the science behind the smell of thermally modified timbers.
The smoky smell of thermally modified wood will fade in time. Abodo’s Vulcan Timber, produced from radiata pine, generally has a lower odour than other modified woods due to the longer processing time.
A surface coating like Abodo Protector will significantly reduce the odour generated by Vulcan timber, which is generally not a concern in exterior applications. In interior applications a low VOC natural oil such as Osmo or Rubio Monocoat will reduce odour and replace it with a natural scent.