---
kind: "section"
citation: "40 C.F.R. § 141.534"
title: "40"
number: "141.534"
heading: "How does my system use this data to calculate an inactivation ratio?"
url: "https://uscodex.org/cfr/40/141.534"
---

# §141.534. How does my system use this data to calculate an inactivation ratio?


Use the tables in [§ 141.74(b)(3)(v)](/cfr/40/141.74.md?p=b-3-v) to determine the appropriate CT99.9 value. Calculate the total inactivation ratio as follows, and multiply the value by 3.0 to determine log inactivation of Giardia lamblia:


## Notes

### Amendments

[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38856, June 29, 2004]

### Source

Source: 67 FR 1839, Jan. 14, 2002, unless otherwise noted.

### Authority

Authority: 42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4, 300g-5, 300g-6, 300j-4, 300j-9, and 300j-11.

### Source

Source: 40 FR 59570, Dec. 24, 1975, unless otherwise noted.

### Amendments

[67 FR 1839, Jan. 14, 2002, as amended at 69 FR 38856, June 29, 2004]