Open systems plunge the loaded carrier straight into liquid nitrogen for the fastest possible cooling. Closed systems seal the sample inside a straw or device first, trading a little cooling speed for isolation from the liquid.
What the evidence does and does not settle
ASRM’s 2021 committee opinion recommends vitrification as standard of care for oocytes and embryos, and notes there are no published reports of actual cross contamination of cryopreserved embryos when open containers are used. So this is a validated risk decision for your laboratory, not a choice the evidence makes for you.
Where the choice follows you
- Storage phase. Laboratories using open devices often move to vapour phase storage, which brings ASRM’s caution about failure potential when level drops, and the case for level probes over temperature probes.
- Transport. A closed straw ships like any other. An open device must stay submerged or in cold vapour throughout the transfer into the shipper.
- Audit. Closed protocols add a sealing step and a seal integrity check to the witnessing record.
- Consumables. Device format dictates the visotube, goblet and canister combination.
Document the reasoning
CBS High Security straws seal with the SYMS or SYMS III sealer in 0.3 ml and 0.5 ml formats. Whichever system you validate, write down why, because it will be asked for.
