# -4 Insulation.

- **operation:** document
- **citation:** 49 CFR 179.220-4
- **title:** -4 Insulation.
- **source type:** regulation
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** current
- **official:** true
- **published on:** Not available
- **effective on:** 2026-08-18
- **summary:** 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]
- **machine formats:** - **json:** https://regulus.evalyn.ai/document/49-cfr-179-220-4.json
- **markdown:** https://regulus.evalyn.ai/document/49-cfr-179-220-4.md
- **app url:** https://regulus.evalyn.ai/document/49-cfr-179-220-4
- **source url:** https://www.ecfr.gov/on/2026-08-18/title-49/section-179.220-4
**body:**

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]
- **truncated:** false
- **body characters:** 153