There was an explosion in the Norwalk Hospital emergency room this weekend.  An oxygen regulator being transported on a gurney at the facility, which is part of the Western Connecticut Health Network, was the cause.  Police say two attendants were transporting a patient when the explosion happened.  An EMT attendant was treated and released.  There were no other injuries reported.  Burn marks on the wall and ceiling resulted from the explosion.  A fire extinguisher was used at the scene.