cil i ties of Ser bia, Bel grade, Ser bia 2 Fac ulty of Me chan i cal En gi neer ing, Uni ver sity of Bel grade, Bel grade, Ser bia 3 Tech ni cal Col lege ^a~ak, ^a~ak, Ser bia Sci en tific pa per

This work con sid ers the man i fes ta tion of spon ta ne ous break downs of Gei ger-Mueller counters. This is an ex per i men tal type of work. The rea sons lead ing to the spon ta ne ous breakdowns of Gei ger-Mueller coun ters have been ana lysed un der con trolled lab o ra tory con ditions. The ex per i ments were car ried out un der the "con stant volt age". The tested Gei ger-Mueller cham bers were com mer cial cham bers of the ra dial elec tric field and ho mog enous elec tric field. The ex per i men tal-sta tis ti cal meth ods were used in or der to choose the cham bers with iden ti cal fea tures (with 0.1 % of sta tis ti cal re li abil ity).The re sults of ex per iments showed that the spon ta ne ous break down of the Gei ger-Mueller coun ter hap pens even in the con di tions of shield ing. They also showed that those break downs have cu mu la tive features. The rea son for that is a pos i tive feed back be tween the spon ta ne ous break downs. The ex pla na tion is con firmed and quan ti fied by the work ing gas fil ter ing ex per i ments.