The heaters are primarily made up of carbon fibers that are contained in a matrix of glass fibers.
During the manufacturing process we add micro-fine particles of ceramic powder for improved emissivity.
The heater is then held for a prescribed period (hours) in a "hot press" of very high pressure (many tons) and high heat. This process "sinters" the components of the heater so they are never subject to any out-gassing.
We have done VOC testing that verifies this. Please see the following website for further explanation: http://www.healwithheat.com/home/getdetail/true-wave-trade-heater-technology