It is often convenient to separate the species chemical production rates into creation and destruction rates. Furthermore, some numerical approaches take advantage of this separation. Therefore, we provide subroutines that return the chemical rates in the following form:

(3–51)

where, for non-three-body reactions, the creation rate is

(3–52)

and the destruction rate is

(3–53)

When third body reactions are involved, each sum in the above equations is multiplied by the third-body concentration

Another useful form for the chemical production rates is found by defining a creation rate and characteristic time for the destruction rate, that is,

(3–54)

Here the characteristic time for destruction is given in terms of as

(3–55)

As a precaution against and simultaneously approaching zero, the Gas-phase Kinetics implementation of the destruction time is written as

(3–56)

where is an arbitrary small number, say .