An apparatus, such as an ALD (Atomic Layer Deposition) apparatus, including a precursor source configured for depositing material on a heated substrate in a deposition reactor by sequential self-saturating surface reactions. The apparatus includes an in-feed line for feeding precursor vapor from the precursor source to a reaction chamber and a structure configured for utilizing heat from a reaction chamber heater for preventing condensation of precursor vapor into liquid or solid phase between the precursor source and the reaction chamber. Also various other apparatus and methods are presented.