brussels sweet smell waffle familiar belgium thursday people leave choke fire waffle factory send dense black cloud across brussels disrupt rail traffic capital police say blaze milcamps factory produce national sweet treat various regional variants break lunchtime immediately clear start whether anyone hurt lot smoke emit advise people keep doors windows shut stay inside drivers close air vent cars local police say sharp smell burn waffle cause cough city center km miles blaze belgian waffle traditionally sell mobile vendors street kiosks become popular around world batter cook hotplates pattern accord various regional traditions dust ice sugar history date back wafers bake mass medieval monasteries low countries burn cake belgian waffle fire choke brussels