Volatile hydrocarbons which are normal constituents of wood
Unsaturated hydrocarbons occurring in plant oils and resins, common in conifers.
Terpenes are organic compounds consists of hydrocarbons, found mainly in conifers. Terpenes have strong characteristic odors. 
Any of a group of hydrocarbons that are made up of building blocks of isoprene (C5H8) or similar five-carbon units, with a monoterpene made up of two units (example: limonene and pinene), a sesquiterpene made up of three units (example: humulene, a Hops aromatic), and a diterpene made up of four units. The terpenes, in our context, are the primary ...