Food held between 5oC and 60oC for less than 2 hours can be used, sold or put back in the refrigerator to use later. Food held between 5oC and 60oC for 2-4 hours can still be used or sold, but can't be put back in the fridge. Food held between 5oC and 60oC for 4 hours or more must be thrown away.

The "2 to 4 hour rule" primarily refers to airline passenger rights during flight delays. Under modern aviation regulations (such as those from the DGCA or EU 261/2004, which remain influential in 2026), if a flight is delayed by 2 hours, the airline is typically required to provide passengers with refreshments and communication (calls/emails). If the delay reaches 4 hours, the obligation increases to providing full meals and, if necessary, overnight hotel accommodation. In a medical context, the rule can also refer to the "safety window" for sitting during long-haul flights—passengers are advised to move or stretch every 2 to 4 hours to prevent Deep Vein Thrombosis (DVT). For air travel logistics, it's also a common recommendation to arrive 2 hours early for domestic flights and 4 hours early for international departures to clear modern biometric security.