# Cold boxes.

- **operation:** document
- **citation:** 49 CFR 193.2421
- **title:** Cold boxes.
- **source type:** regulation
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** historical
- **official:** true
- **published on:** Not available
- **effective on:** 1999-10-01
- **summary:** (a) Each cold box in a liquefaction system must be equipped with a means of monitoring or detecting, as appropriate, the concentration of natural gas in the insulation space.

(b) If the insulation space in a cold box is designed to operate with a gas rich atmosphere, additional natural gas must be 
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- **markdown:** https://regulus.evalyn.ai/document/49-cfr-193-2421.md
- **app url:** https://regulus.evalyn.ai/document/49-cfr-193-2421
- **source url:** https://www.govinfo.gov/app/details/CFR-1999-title49-vol3/CFR-1999-title49-vol3-sec193-2421
**body:**

(a) Each cold box in a liquefaction system must be equipped with a means of monitoring or detecting, as appropriate, the concentration of natural gas in the insulation space.

(b) If the insulation space in a cold box is designed to operate with a gas rich atmosphere, additional natural gas must be introduced when the concentration of gas falls to 30 percent.

(c) If the insulation space of a cold box is designed to operate with a gas free atmosphere, additional air or inert gas, as appropriate, must be introduced when the concentration of gas is 25 percent of the lower flammable limit.
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- **body characters:** 593