Medium density fibreboard (MDF) is made from lingo-cellulosic fibres derived from defibrated wood chip. It is typically composed of 85-100% softwood and 0-15% hardwood. The material is often bound together with a urea-formaldehyde resin. It may leach out formaldehyde vapour in storage, and the resin can decompose when machined due to heat and gives out formaldehyde.