Intro cleanup   I cut this sentence out of the introduction   In the United States federal safety laws require that window glass be tempered if each of the following criteria are met sill height within  in  m of the floor top edge greater than  in  m from the floor area greater than  ft  m and horizontal distance to nearest walking surface of less than  in  mhttpwwwdiychatroomcomfwhentemperedglassrequiredpost  There are couple problems with that where it was  It cluttered the intro and went into way too much detail on a particular tangent interrupting the flow of reading  Its inclusion in the intro such detail also places undue weight on this particular regulation in the US  also too much US focus  That said it is referenced and somewhat interesting so it might fit somewhere else in the article  maybe in a new section on regulations requiring tempered glass in various applications