Replacing Window Panes
If you must replace a window with the sash in position, use this technique to prevent injury
When replacing a window, it's a good idea to carefully remove the sash before attempting to pull out the old window. That way, you eliminate the possibility of getting injured by shattered glass when prying the window frame off the house.
If that's not possible because the sash is fixed, such as for a large picture window, stabilize the glass with 2-inch-wide duct tape. Place two strips of tape in an X pattern to both the interior and exterior surfaces of the pane. Now, if the glass does crack, the tape will prevent any large shards from falling out. When handling windows, be sure to wear heavy leather gloves and eye protection.