The procedure replaces most of the oxygen in the package with other gases including small amounts of carbon monoxide (used in factory-wrapped or case-ready) meat. Those gases, which react with the color in meat, generate a red color. The shelf life for ground beef sealed in that mix of gases can be extended from about 14 days to 28 days, and about 10 days to 35 days for whole cuts.

Some supermarket chains, including Kroger and Publix, decline to carry meat packaged with carbon-monoxide, because of concerns as regards to appearance and quality.
Bacterial counts that point to spoilage in meat may make it taste and smell bad, but food safety experts say that it is generally not a health hazard. Thorough cooking will kill bacteria that cause food borne illness, though it won’t necessarily undo spoilage odors or bad taste.
The U.S. Food and Drug Administration determined as recently as July 2004 that it had no objections to the use of carbon-monoxide packaging for fresh meat.
WHAT YOU CAN DO
- Ask whether your grocer sells meat packed with carbon monoxide.
- If so, don’t use color as the only guide to freshness.
- Buy meat whose stamped date is a couple of weeks away.
- With all meat, check for signs of spoilage, such as surface slime.
- Always throw away meat that smells bad.