SIL stands for Safety Integrity Level. A SIL is a measure of safety system performance, or probability of failure on demand (PFD). The higher the SIL level, the lower the probability of failure on demand for the safety system and the better the system performance.
| Probability of Failure on Demand (PFD) |
Safety Availability in % |
Risk Reduction Factor |
|
| SIL 1 | 0.01 – 0.1 | 90 – 99 | 10 – 100 |
| SIL 2 | 0.01 – 0.001 | 99 – 99.9 | 100 – 1000 |
| SIL 3 | 0.001 – 0.0001 | 99.9 – 99.99 | 1000 – 10000 |
