  The asymmetry of line profiles, i.e., the secondary component, is crucial to
understanding the energy release of coronal holes (CH), quiet sun (QS), and
bright points (BPs). We investigate the asymmetry of Si IV 1393.75 {\AA} of the
transition-region (TR) line recorded by Interface Region Imaging Spectrometer
(IRIS) and co-spatial-temporal Atmospheric Imaging Assembly (AIA) and
Helioseismic and Magnetic Imager (HMI) data onboard Solar Dynamics Observatory
(SDO) for three time series on 26 April 2015, 24 July 2014, 26 July 2014. Most
asymmetric profiles are in the complex magnetic field regions of the networks.
The asymmetric profiles are fitted with both single and double Gaussian models.
The mean value of Doppler velocity of the second component is almost zero (with
a significant standard deviation) in QS/CH, which may indicate that the
physical process to trigger the secondary Gaussian originates at the formation
height of Si IV. While the mean Doppler velocity from secondary Gaussian in BPs
is around +4.0 km/s (redshifted). The non-thermal velocities of the secondary
Gaussian in all three regions are slightly higher than the single Gaussian. The
statistical investigation leads to the prevalence of blueshifted secondary
components in QS/CH. However, secondary Gaussian in the BPs redshifted, i.e.,
the BPs redshift behavior could be interpreted due to the site of reconnection
located above the formation height of the Si IV line. The peak intensity of the
second component for all three regions is likely to follow a power law that is
a signature of the small-scale flaring-like trigger mechanism.
