Index value

Contamination classes [2]

mC_d < 1.5

Nil to very low degree

2.0 ≤ mC_d < 4.0

Moderate degree

4.0 ≤ mC_d < 8.0

High degree

8.0 ≤ mC_d < 16.0

Very high degree

16.0 ≤ mC_d < 32.0

Extremely high degree

mC_d ≥ 32.0

Ultra-high degree