Labor-intensive, manual process
Possibility of variation between lab personnel and each culture
Numerous open steps through the process
Temperature fluctuations as flasks are moved in and out of the incubator
Manual pipette process to feed cells and remove waste
Cell harvest spans hours/days**
Variable surface area**
Current good manufacturing practice (cGMP)-grade clean room, hood, incubator and storage for flasks
**Dependent on the number and capacity of flasks