Answer
A single EPSP has a voltage of only about 0.5 mV. (.03 to 6 mV). Threshold for most neurons is about -55 mV which can only be reached by application of a stimulus voltage of at least 15 mV. The voltage of a single EPSP is therefore too small (low) to trigger an action potential.
Work Step by Step
The resting potential of neurons is about -70 mV. Since threshold is about -55 mV, a stimulus must be about +15 mV to trigger an action potential (AP). The voltage of an individual EPSP is much to small to trigger an AP.
