I think it depends on the brand you are using. I teach if there are risk factors where you might be doing any form of PPV to open it out of the package and set it up with Tpiece/mask set up (or whatever they are using for PPV). Some expire in 24 hours once out of the package, some have a pull tab so when the package is opened they don't necessarily expire because the pull tab isn't pulled and can be used. They just need to understand that they have to pull the tab to activate the use of the colormetric CO2 detector. I hope this helped.