# -4 Insulation.

**Citation:** 49 CFR 179.220-4  
**Type / status:** regulation / current  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** 2026-08-18  
**Published:** Not stated

The annular space between the inner container and the outer shell must contain an approved insulation material.

[Amdt. 179-9, 36 FR 21340, Nov. 6, 1971]

## Document text

The annular space between the inner container and the outer shell must contain an approved insulation material.

[Amdt. 179-9, 36 FR 21340, Nov. 6, 1971]

## Provenance

- Official: Yes
- Source: <https://www.ecfr.gov/on/2026-08-18/title-49/section-179.220-4>
- Source ID: `ecfr`
- SHA-256: `600fc90ba79f89bfc8c310d90d5a705ced740fdad9b0dd3b3d76a390b97b390f`
- Retrieved: 2026-08-20T05:46:20.606Z
- Exported: 2026-08-22T00:48:10.945Z
- Document slug: `49-cfr-179-220-4`

### Source metadata

```json
{
  "cfrTitle": 49,
  "part": "179",
  "section": "179.220-4",
  "subpart": "Subpart D—Specifications for Non-Pressure Tank Car Tanks (Classes DOT-111AW, 115AW, and 117AW)",
  "corpusVersion": "2026-08-18",
  "jurisdiction": "US"
}
```