---
kind: "section"
citation: "49 C.F.R. § 173.335"
title: "49"
number: "173.335"
heading: "Chemical under pressure n.o.s."
url: "https://uscodex.org/cfr/49/173.335"
---

# §173.335. Chemical under pressure n.o.s.

- (a) **General requirements.** A cylinder filled with a chemical under pressure must be offered for transportation in accordance with the requirements of this section and [§ 173.301](/cfr/49/173.301.md) (except for the cylinder valve cap requirements in §§ [173.301(a)(11)](/cfr/49/173.301.md?p=a-11) and [(12)](/cfr/49/173.301.md?p=a-12)). In addition, a DOT specification cylinder must meet the requirements in §§ [173.301a](/cfr/49/173.301a.md), [173.302](/cfr/49/173.302.md), [173.302a](/cfr/49/173.302a.md), and [173.305](/cfr/49/173.305.md), as applicable. UN pressure receptacles must meet the requirements in §§ [173.301b](/cfr/49/173.301b.md), [173.302b](/cfr/49/173.302b.md), and [173.304b](/cfr/49/173.304b.md), as applicable. Where more than one section applies to a cylinder, the most restrictive requirements must be followed.
- (b) **Filling limits.** Cylinders must be filled so that at 50 °C (122 °F) the non-gaseous phase does not exceed 95% of their water capacity and they are not completely filled at 60 °C (140 °F). When filled, the internal pressure at 65 °C (149 °F) must not exceed the test pressure of the cylinder. The vapor pressures and volumetric expansion of all substances in the cylinders must be taken into account.
- (c) **Minimum service pressure.** The minimum service pressure must be in accordance with the design specifications of [part 178](/cfr/49/part178.md) of this subchapter for the propellant. In any case the minimum test pressure must not be less than 20 bar.
- (d) **Periodic inspection.**
  - (1) Except as specified in (d)(2) of this section, the maximum requalification test period for cylinders transporting chemical under pressure n.o.s. is 5 years.
  - (2) For cylinders with maximum capacity of 450 L or less and filled with materials used as fire extinguishing agents, the maximum requalification test period is 10 years.

## Notes

### Amendments

[78 FR 1092, Jan. 7, 2013, as amended at 82 FR 15891, Mar. 30, 2017; 83 FR 55810, Nov. 7, 2018; 85 FR 83401, Dec. 21, 2020; 87 FR 44997, July 26, 2022]

### Authority

Authority: 49 U.S.C. 5101-5128, 44701; 49 CFR 1.81, 1.96 and 1.97.

### Amendments

[78 FR 1092, Jan. 7, 2013, as amended at 82 FR 15891, Mar. 30, 2017; 83 FR 55810, Nov. 7, 2018; 85 FR 83401, Dec. 21, 2020; 87 FR 44997, July 26, 2022]