How much time a component can exceed working conditions before a component needs to be baked before the reflow process occurs when soldering a sensitive component to a PCB. If this time is exceeded and the component is not baked, the component might contain moisture and when reflowing it onto a PCB, it might become damaged.

MSL LevelWorking TimeWorking Conditions
1Unlimited≤30℃/85%RH
21 Year≤30℃/60%RH
2a4 Weeks≤30℃/60%RH
3168 Hours≤30℃/60%RH
472 Hours≤30℃/60%RH
548 Hours≤30℃/60%RH
5a24 Hours≤30℃/60%RH
6Use Immediately≤30℃/60%RH