Nearly all jurisdictions in the United States enforce codes that require two exit stairwells in residential buildings above three or four stories. Housing advocates say that increasing the cap to six stories will lead to better housing options and lower costs. That logic has persuaded lawmakers in some U.S. states to pass laws that raise the allowed height of single exit stair buildings, bypassing state building codes. These changes have alarmed fire officials, who say that having taller buildings with only one stairwell puts the lives of residents and firefighters at risk. With that as the...