valves to isolate the system to be opened, and tag these valves to ensure they remain shut while you are working on the equipment. Wear proper protective clothing. Do not try to take shortcuts and do not skylark. Carelessness has been a factor in nearly all reported mishaps involving steam. Observe all appropriate precautions. CLOSED COMPARTMENTS AND UNVENTED SPACES Never enter a closed space until it is certified safe by a gas free engineer. Closed  compartments  may  contain  hidden dangers, both to yourself and to the ship as a whole. One possibility  is  toxic  or  explosive  gases.  After  these spaces  are  opened,  your  gas  free  engineer  will  make sure that it s safe for you to work there. If  the  ship’s  been  damaged,  other  dangers  may exist. The manhole access cover to a damaged tank or compartment  might  be  all  that’s  preventing  flooding. Additionally,  water  entering  a  closed  compartment pressurizes  the  air  already  there.  Don’t  try  to  open  a pressurized  compartment  or  void  without  venting  the pressure  first.  If  you  don’t  vent  the  pressure  first,  the hatch  cover/access  will  fly  open  violently,  possibly injuring you or a shipmate. Check with your supervisor for  help  in  learning  to  recognize  these  and  other hazards. Consider  all  compartments  dangerous  if  they’ve been  closed  for  any  length  of  time.  If  the  bulkheads, deck,  or  overhead  are  rusted,  they  have  absorbed oxygen  from  the  air.  This  means  there  may  not  be enough  oxygen  left  for  you  to  breathe.  If  the compartment  was  painted  before  it  was  closed,  the hardening  paint  has  absorbed  oxygen  and  given  off carbon  monoxide.  Carbon  monoxide  is  particularly dangerous  because  it  gives  no  warning.  If  you’re working in a compartment that’s been closed and you notice a sudden feeling of weakness, drowsiness, or a slight headache, call for help and get to fresh air. In storage compartments, several toxic gases may be generated by mildewing or rotting foodstuffs or by materials such as cloth, leather, and wood. Mildewing and rotting are speeded up when the space is warm and humid, such as when a ship is cruising in the Tropics or when an area has been flooded as a result of damage or accident. Carbon dioxide is frequently found in refrigerator spaces, even though the spaces are undamaged and the foodstuffs  are  still  good.  This  condition  results  from lack of ventilation and the fact that foods slowly absorb oxygen and give off carbon dioxide. If personnel stay in such spaces longer than a few minutes at a time, they may be overcome and eventually suffocate. Sulfur oxides are acrid, corrosive, poisonous gases produced when fuels containing sulfur are burned. For example,  aboard  ship  the  primary  producer  of  sulfur oxides is fuel oil, which contains sulfur as an impurity. Government agencies and industries have sought to reduce sulfur oxide emissions in three ways: 1.   Switching  to  low-sulfur  fuels  (those  with  less than 1% sulfur). 2.   Removing sulfur from fuels entirely. 3.   Removing  sulfur  oxides  from  combustion gases. To reduce the sulfur oxide problem on ships, the Navy developed a fuel oil called Navy distillate fuel. Sulfur  oxides  produce  an  offensive  odor  and  can cause  eye  and  lung  irritation.  Tanks  that  have  held petroleum  products  and  compartments  in  which  oil, gasoline, solvents, and organic products that have been spilled will contain the vapors of these products. Tanks  that  have  held  petroleum  products,  and compartments  in  which  oil,  gasoline,  solvents,  and organic products have been spilt, will contain the vapors of these products. You  must  assume  that  any  closed  space,  double bottom,  tank,  cofferdam,  pontoon,  or  void  contains gases that can poison or suffocate you or can explode. (NOTE: Never enter any such space until it has been thoroughly  ventilated  and  checked  by  a  gas  free engineer to make sure there is no danger of poisoning, suffocating,  or  igniting  flammable  gases.)  Before entering  a  closed  space,  make  sure  that  it’s  been ventilated for 24 hours. Also, the gas free engineer must certify the safety of the space and recertify it every 8 hours while personnel are working in the space. Always have  a  person  stationed  at  the  entrance  to  maintain 19-9 Student Notes: