  One of the main objectives of the CREDO project is to search for so-called
Cosmic-Ray Ensembles (CRE) \cite{homola2020cosmic}. To confirm the existence of
such phenomena a massive scale observation of even relatively low energy
Extensive Air Showers (EAS) and an analysis of their correlations in time must
be performed. To make such observations possible, an infrastructure of widely
spread detectors connected in a global network should be developed using
low-cost devices capable of collecting data for a long period of time. For each
of these detectors or small detector systems the probability of detection of an
EAS has to be determined. Such information is crucial in the analysis and
interpretation of collected data. In the case of large number of systems with
different properties the standard approach based on detailed and extensive
simulations is not possible, thus a faster method is developed. Knowing the
characteristics of EAS from more general simulations any required probability
is calculated using appropriate parameterization taking into account EAS
spectrum, energy dependence of particle density and zenith angle dependence.
This allows to estimate expected number of EAS events measured by a set of
small detectors \cite{Karbowiak_2020} and compare results of calculations with
these measurements.
