Small insert solenoids have been built using a multifilamentary Ag/Bi 2 Sr 2 CaCu 2 O x round wire insulated with mullite sleeve (~100 µm in thickness), and characterized in background fields to explore the quench behaviors and limits of Bi 2 Sr 2 CaCu 2 O x superconducting magnets, with an emphasis on assessing the impact of slow normal zone propagation on quench detection. Using heaters of various lengths to initiate a small normal zone, a coil was quenched safely more than 70 times without degradation, with the maximum coil temperature reaching 280 K. Coils withstood a resistive voltage of tens of mV for seconds without quenching, showing the high stability of these coils and suggesting that the quench detection voltage shall be greater than 50 mV to not to falsely trigger protection. The hot spot temperature for the resistive voltage of the normal zone to reach 100 mV increases from ~40 K to ~80 K with increasing the operating wire current density J o from 89 A/mm 2 to 354 A/mm 2 whereas for the voltage to reach 1 V, it increases from ~60 K to ~140 K, showing the increasing negative impact of slow normal zone propagation on quench detection with increasing J o and the need to limit the quench detection voltage to < 1 V. These measurements, coupled with an analytical quench model, were used to access the impact of the maximum allowable detection voltage and temperature upon quench detection on the quench protection, assuming to limit the hot spot temperature to <300 K.