It is assumed that terpenoids in biomass-derived fuels have important influences on forest fires due to their enormous flammability. The fires consuming terpenoid-rich fuels always burn violently and spread fast. But the mechanism how terpenoids influence occurrence and propagation of fires are little known. Some terpenoids are volatile organic compounds (VOC) as they are released from vegetation and litter in natural environment. Hence, they contribute to the characteristic composition of the ambient air. Many studies have reported terpenoid emissions in natural environment from different perspective. Nevertheless there are only a few studies concerning terpenoid emissions from heated fuels. The present study explored the differences in terpenoid emissions from needles of Pinus sylvestris var. mongolica under natural and heated conditions. Terpenoids were sampled on Tenax-TA and analyzed using Thermal Desorption– Gas Chromatography–Mass Spectrometry (TD–GC–MS). The results showed that the emission rate of terpenoid from P. sylvestris in natural environment was low (0.167 lg g1 h1 DW). However, terpenoid emissions dramatically increased at the temperature of 200 C, with a major component, a-pinene. Within 15 min, the emission of terpenoids emitted by heated needles was up to 16.314 lg g1 DW for total and 10.321 lg g1 DW for a-pinene. These considerable emissions of terpenoids from heated needles will have great influences on occurrence and propagation of forest fires. 2011 Ecological Society of China.