The invention relates to an electrical circuit breaker comprising an arc formation chamber and an arc extinguishing chamber, the arc formation chamber being at least partially bounded by a side flange or at least a part of a side wall consisting of a polymeric composition comprising a thermoplastic polymer, a triazine based flame retardant, at most 0-5 wt. % of phosphorous or halogen containing flame retardants, and 0-15 wt. % of a reinforcing agent, wherein thermoplastic polymer comprises a polyamide with a melting temperature of at least 260° C. and the triazine based flame retardant comprises at least 20 wt. % of melam, wherein the weight percentages (wt. %) are relative to the total weight of the polymeric composition.