How long should I wait before opening the lab vacuum drying oven after a cycle?

After a cycle in your lab vacuum drying oven, the safest practice is to wait until the chamber temperature has fallen below 60 °C and the pressure has returned to atmospheric. Most manufacturers of a modern lab vacuum drying oven recommend a minimum cooling period of 30 minutes, but a full load can extend this to an hour. 

First, turn off the heater and allow the lab vacuum drying oven to depressurize by slowly opening the vent valve; never force the door while vacuum remains . 

While you wait, record the time and temperature in your logbook so every future user of the lab vacuum drying oven knows exactly how long cooling takes under comparable loads. When the display shows 50 °C or lower and the gauge reads zero vacuum, open the door a few centimetres to let tempered air circulate for another five minutes; this prevents condensation on delicate samples. By consistently following these steps, you protect both the contents and the long-term reliability of your lab vacuum drying oven.