What is the definition of a retail facility?

A flammable substance listed in 40 CFR §68.130 is excluded from the Risk Management Program regulations when it is used as a fuel or held for sale as a fuel at a retail facility (§68.126). What is the definition of a retail facility for the purposes of this exclusion?

A retail facility is defined as a stationary source at which more than one-half of the income is obtained from direct sales to end users or at which more than one-half of the fuel sold, by volume, is sold through a cylinder exchange program (§68.3).