The purpose of double wrapping is to prevent non-kosher food from entering the meal and “contaminating” it with non-kosher food. Two layers are used “in case” something gets through the first layer.

The accepted procedure by the Kosher community, including most kosher certifying bodies and chaplains, follows. This is applicable only to the stand-up plastic pouches, not the foil pouches.

Wipe out any noticeable spills in the microwave. Vent the stand-up, plastic pouch by pulling the corner back slightly at the tear notch and stand it on a paper plate. Place a simple covering over the pouch using, for example, an upside-down plastic or paper bag, or plastic wrap. Put the meal in the microwave and warm for one (1) minute. (NOTE: Even though the time depends on power settings & altitude, one (1) minute is usually long enough in most microwaves.)

The outer covering or bag becomes one of the two layers of double wrapping and the slightly vented plastic pouch is the second layer. Since steam is going out of the vented corner as the meal warms, the rabbis have determined that the opening for venting does not negate the double wrapping requirement. The consumer could always put another paper plate, paper towel or napkin under and above the pouch for further protection if they feel more comfortable for any reason.