LeakCheck is highly sensitive with a response of less than 1 second to even the smallest of leaks (1 x 10-7). Clear down is also less than 1 second and importantly the instrument is unaffected by large leaks - even 100% SF6 will not contaminate the detector.
Also available from Ion Science is GasCheck SF6 including a highsense version detecting leaks as small as 1 x 10-8 ml/sec)