The IDF Home Front Command Update issued an updated advisory to Israeli civilians on Friday, warning them to keep their bomb shelter windows closed with the double layer of protection.
Guidelines Concerning Protective Room Windows
The window in a residential protective room (mamad) has two parts – an inner window made from glass, and an outer window cover made from steel.
Due to the security situation, it is important to be ready in advance in case an alert is received in your area. For that reason, make sure that the steel outer window is closed at all times. ((This may not be reasonable unless you live in the South, but if it’s a swing-plate it should be partially closed or close enough to easily grab and close. If it’s a slide, again they should be rolled partially and ready to be easily closed. This is often a problem as they are usually kept fully open and can get stuck or rusty.))
In addition, make sure that the glass window is also closed at all times, with the exception of those residential protective rooms which have a double-wing window, as those should be removed immediately. ((I have no idea what they are talking about. The problem is, with a close rocket strike the glass inside the protected room may shatter and become shrapnel and unfortunately there was no requirement that these windows have car-like safety glass. If the glass window can be removed and taken out of the room, it may make sense to do so.))
((There has also been a suggestion to lie down in a mamad, below the height of the steel covered window, as in Sderot a piece of shrapnel had enough force to pierce the metal window cover and kill.))