Actually the T25 flasks are not completely air locked systems.The caps of flasks have a filter(which ensures a sterile environment) permits exchange of gases.
Actually the T25 flasks are not completely air locked systems.The caps of flasks have a filter(which ensures a sterile environment) permits exchange of gases.
There are two types of flasks: 1) the ones with the white filter in the caps (as mentioned in an earlier answer); and 2) the ones without the filter membrane; those need to have the cap not thightly closed, so that the air and CO2 can get into the flasks. This is similar to Petri dishes, where there is a little gap allowing air exchange.