A pierceable cap 411 may be used for containing sample specimens during storage and transport. The pierceable cap 411 may prevent unwanted escape of sample specimen before transfer with a transfer device 43. The pierceable cap 411 may fit over a vessel 21. An access port in the pierceable cap 411 may allow passage of a tip 41 of a transfer device 43 through the pierceable cap 411. Single or multiple frangible layers 415, 416 may be disposed across the access port. Single frangible layers 415, 416 are configured to prevent venting upon initially being pierced by a transfer device 43 but to allow venting as the transfer device 43 is advanced through the frangible layer 415, 416.