Good pressure cookers are designed to produce immense pressure by heating water and converting it into steam. Unlike conventional cookers, this steam is locked inside with only a small percentage of it being allowed to escape through a vent tube. This effectively creates a high pressure, high temperature environment which quickens the cooking process.
It is pretty normal for steam to force its way out through the overpressure valve at the beginning because sometimes the internal pressure is not sufficient to activate this valve. There is however, no need to worry about this because it actually plays an important role in removing cold air from inside your cooker. If the overpressure valve however gives in to pressure and allows steam to escape midway, you may want to check if it is in its correct position. Remember, for safety reason, you can only open a pressure cooker when pressure is at its minimum. You may want to replace your valve if the leaks are persistent.
What happens when you put your pressure cooker in cold water is that first the pressure inside it declines dramatically. This creates a temporary vacuum. A whistling sound is produced as air gushes into fill up this void. As such, the whistling sound should not be a cause of worry.
There are various reasons why this may happen. The most common reason is inadequate heat supply and this can be overcome by setting the cooker on high heat to allow for pressure to build up. Another common reason is if the control is not seated correctly on the vent tube. Be sure to check for this and correct. Your cooker may also fail to come up to pressure if the cover handle is leaky or cracked – in this case you will need to replace it with a new one.
Quick Pressure Release is a method that brings the pressure cooking process to an almost immediate stop. You simply turn off the unit, pull the handle of the valve forward using tongs. This will give way for steam to be released immediately. Once pressure is completely removed, the indicator will drop effectively unlocking the lid to open.
This is the normal cooling process of a pressure cooker whereby you turn the appliance off and allow pressure to drop gradually. This may take anywhere between 12 and 30 minutes. Once pressure is fully emitted, the indicator drops and the lid usually unlocks to open.
If used properly, pressure cookers are safe. However, since they are high-pressure steam devices, it is important to ensure older pots are regularly checked just to be sure the valves are screwed in properly. But generally, a good equipment + good care + regular checks = happy cook.