---
kind: "section"
citation: "33 C.F.R. § 157.164"
title: "33"
number: "157.164"
heading: "Use of inert gas system."
url: "https://uscodex.org/cfr/33/157.164"
---

# §157.164. Use of inert gas system.

- (a) The master of a tank vessel having a COW system under [§ 157.10(e)](/cfr/33/157.10.md?p=e), [§ 157.10a(a)(2)](/cfr/33/157.10a.md?p=a-2), or [§ 157.10c(b)(2)](/cfr/33/157.10c.md?p=b-2) shall ensure the following:
  - (1) Before each cargo tank is crude oil washed, the oxygen content in the tank is measured at each of the following locations in the tank:
    - (i) **One meter from the deck.**
    - (ii) **In the center of the ullage space.**
  - (2) Before each cargo tank with partial bulkheads is crude oil washed, each area of that tank formed by each partial bulkhead is measured in accordance with [paragraph (a)(1)](#a-1) of this section.
  - (3) Before each cargo tank is crude oil washed, the oxygen content in that tank is 8 percent or less by volume at the locations under [paragraph (a)(1)](#a-1) of this section.
  - (4) **During COW operations, the following are maintained in each cargo tank being crude oil washed—**
    - (i) **A gas or a mixture of gases with an oxygen content of 8 percent or less by volume.**
    - (ii) **A positive atmospheric pressure.**
  - (5) During COW operations, a crew member monitors the instrumentation under [46 CFR 32.53-60(a)(1)](/cfr/46/32.53-60.md?p=a-1), except if that instrumentation has an alarm that sounds in the cargo control room when the oxygen content exceeds 8 percent by volume.
- (b) Crude oil washing of the cargo tanks must be terminated when [paragraph (a)(4)](#a-4) of this section is not met and crude oil washing of that tank may not be resumed until the requirements of [paragraph (a)(4)](#a-4) of this section are met.

## Notes

### Amendments

[CGD 77-058b, 45 FR 43709, June 30, 1980, as amended by CGD 82-28, 50 FR 11628, Mar. 22, 1985]

### Source

Source: CGD 77-058b, 45 FR 43709, June 30, 1980, unless otherwise noted.

### Authority

Authority: 33 U.S.C. 1903; 46 U.S.C. 3703, 3703a (note); Department of Homeland Security Delegation No. 0170.1. Subparts G, H, and I are also issued under section 4115(b), Pub. L. 101-380, 104 Stat. 520; Pub. L. 104-55, 109 Stat. 546.

### Source

Source: CGD 74-32, 40 FR 48283, Oct. 14, 1975, unless otherwise noted.

### Amendments

[CGD 77-058b, 45 FR 43709, June 30, 1980, as amended by CGD 82-28, 50 FR 11628, Mar. 22, 1985]