  The operations of Resistive Plate Chambers in LHC experiments require
Fluorine based (F-based) gases for optimal performance. Recent European
regulations demand the use of environmentally unfriendly F-based gases to be
limited or banned. In view of the CMS experiment upgrade, several tests are
ongoing to measure the performance of the detector with these new ecological
gas mixtures, in terms of efficiency, streamer probability, induced charge and
time resolution. Prototype chambers with readout pads and with the standard CMS
electronic setup are under test. In this paper preliminary results on
performance of RPCs operated with a potential eco-friendly gas candidate
1,3,3,3-Tetrafluoropropene, commercially known as HFO-1234ze, with CO2 and CF3I
based gas mixtures are presented and discussed for the possible application in
the CMS experiment.
