The mass of flammable material produced by a continuous vertical fuel-gas release into air is expressed in closed form, simultaneously incorporating the major effects of (a) release momentum, (b) release positive or negative buoyancy, (c) finite release area, and (d) inert carrier gas. Previous results are recovered in the extremes of a pure momentum release and a pure buoyant-point source release. A vertical release of a volatile liquid fuel is also considered and it is shown that the flammable mass within the evaporating and cooling release "cloud" can be calculated to good accuracy from the formula derived for the negatively buoyant fuel gas release, providing that a simple numerical adjustment is made to the release Froude number. Finally, it is demonstrated that the mass of flammable material arising from a continuous volatile liquid fuel release issued at angles of inclination that range between zero degrees (i.e. horizontal releases) to about 45degrees can be accurately estimated from a simple axisymmetric momentum-controlled jet dilution model.