The effects of C5H10, C6H14, C7H10 and C8H18 on the energy outputs of D2O and CH3F and their mixture D2O-CH3F pulsed optically pumped FIR lasers has been studied experimentally. It is shown that all of them can increase the energy outputs at 66μm, 114μm and 385μm lines from D2O and at 496μm line from CH3F. Especially the net increases at long wavelengths (385μm and 496μm) are up to 30~90% by adding these vapours. Authors account such effects for their intense scattering, so more pumping photons trapped by active molecule, and for the large vibrational heat content relative to theix molecular weight, so the “bottleneck” effect can be decreased.