3.0.22 ctcss problem #rsp1a



I have noticed that even though I set ctcss tone to receive only when signal+tone option are met - despite this I keep receiving some noise - and my squelch is around 80% on NFM.. I am positive nothing transmits now on that frequency, but still I keep hearing noises like when you turn the squelch off for few seconds. Maybe I am doing something wrong.. but when I set a ctcss/dcs on a scanner and I set squelch to 0 I hear nothing unless signal+ctcss/dcs are present.. 
What "level" in dB next to ctcss should I use?