  The Multigap Resistive Plate Chamber (MRPC) is a gaseous detector; the
performance depends very much on the gas mixture as well as the design. MRPCs
are used as a timing device in several collider experiments and cosmic ray
experiments thanks to the excellent timing performance. The typical gas
mixtures of RPC-type detectors at current experiments are based on the gases
$\rm C_2F_4H_2$ and $\rm SF_6$. These gases have very high Global Warming
Potential (GWP) values of 1430 and 23900 respectively.
  The present contribution has been performed as a part of efforts to reduce
the amount of greenhouse gases used in high energy experiments. The performance
of MRPC has been measured with two different gas mixtures; $\rm C_2F_4H_2$
based gas mixtures and the ecological $\rm C_3F_4H_2$ (HFO-1234ze). A small
MRPC was used for the tests. It has an sensitive area of 20 $\times$ 20 $\rm
cm^2$; it was been built with 6 gaps of 220 $\mu$m.
  In normal operation, the strong space charge created within the gas avalanche
limits the avalanche's growth. $\rm SF_6$ plays an important part in the
process due to its high attachment coefficient at low electric fields. It is
thus necessary to find another gas that has a similar attachment coefficient.
$\rm CF_{3}I$ is a possible candidate. Tests were performed with this gas added
to $\rm C_3F_4H_2$.
