  We study the efficiency of nonspinning waveform templates in gravitational
wave searches for aligned-spin binary black holes (BBHs). We use PhenomD, which
is the most recent phenomenological waveform model designed to generate the
full inspiral-merger-ringdown waveforms emitted from BBHs with the spins
aligned with the orbital angular momentum. Here, we treat the effect of
aligned-spins with a single spin parameter $\chi$. We consider the BBH signals
with moderately small spins in the range of $-0.4\leq \chi \leq 0.4$. Using
nonspinning templates, we calculate fitting factors of the aligned-spin signals
in a wide mass range up to $\sim 100 M_{\odot}$. We find that the signals with
negative spins can have higher fitting factors than those with positive spins.
If $\chi = 0.3$, only the highly asymmetric-mass signals can have the fitting
factors exceeding the threshold of 0.965, while the fitting factors for all of
the signals can be larger than the threshold if $\chi = -0.3$. We demonstrate
that the discrepancy between the regions of a positive and a negative spins is
due to the physical boundary ($\eta \leq 0.25$) of the template parameter
space. We also show that the recovered mass parameters can be significantly
biased from the true parameters. We examine the impact of the systematic bias
on the parameter estimation by comparing the bias with the statistical error.
