Fuzzy Risk Graph Model for Determining Safety Integrity Level

Table 1

Definition of SIL's for low-demand mode from IEC 61508-1.

SIL	Range of average PFD	Range of RRF
4	[10^−5,10^−4[	]10^4,10^5]
3	[10^−4,10^−3[	]10^3,10^4]
2	[10^−3,10^−2[	]10^2,10^3]
1	[10^−2,10^−1[	]10^1,10^2]