Quench levels and transient beam losses at HERA

The talk recalls the main parameters which defined the expected (in 1985) beam loss generated quench levels and compares the results with measurements of loss induced quenches at HERA in 1994-2005. The parameters of the BLM system (e.g. calibration, positioning, alarm level, etc.) are discussed and the response of the system to beam loss induced quenches with different time constants are analyzed.