otherwise tamper with the straps without proper authority. Never replace or pull a fuse. Only authorized personnel are allowed to do such work. Motors and generators often have openings in their  casings.  Avoid  dropping  tools  or  other objects into the openings. Some machinery and electrical circuits generate magnetic fields, so be alert; don’t let magnetic tools you are holding be drawn to such equipment. Electrical and electronic equipment and power cables are identified by nameplates, tags, or other markings. Never paint over such identification markings. Don’t hang items on, or secure lines to, any power  cable,  antennas,  wave  guide,  or  other electrical or electronic equipment. Don’t use personal electrical equipment aboard ship without the approval of the engineer officer. COMPRESSED GASES Compressed gases includes air, oxygen, acetylene, carbon  dioxide,  and  other  gaseous  or  gas-forming compounds  held  under  pressure  in  steel  bottles, cylinders, or tanks. In general, three types of hazards are connected with compressed gases as follows: 1.  Cylinders  containing  compressed  gas  are usually round and long. They are made of heavy steel. Unless secured to a structure, they can roll, tip over, or bang  around.  If  not  secured  properly,  they  can  roll around and cause damage by bumping into a person or an object. 2.  T h e c y l i n d e r s c o n t a i n g a s u n d e r pressure—often under very high pressure. A cracked cylinder can fly apart. Air or gas from a valve or hose connected to a cylinder can blow dirt into your eyes; or the hose can whip around and strike you, causing an injury. If you drop or mishandle an oxygen cylinder so that its valve breaks off, you may see the heavy steel bottle  take  off  like  a  rocket—causing  injury  and damage. 3.  The  cylinders  may  contain  gases  that  are poisonous, flammable, or explosive, and often all three. Acetylene cylinders are common aboard ship. If you ignite acetylene, it will blaze with intense heat; if it’s mixed with air and a spark gets to it, it will explode. In fact, an acetylene cylinder can explode if it is overheated and then given a sudden blow. If oxygen comes into contact with oil or grease, you can be sure you will have a fire. CO 2 used in fire extinguishers is particularly dangerous; you will suffocate in a room filled with it. Also, CO 2 is extremely cold when it is discharged. It may cause painful blisters if it comes in contact with your skin. You  must  handle,  work  with,  and  work  around compressed gas cylinders with care and caution. The cylinders are heavy and can easily be tipped. In general, weather-deck stowage will be provided for flammable and explosive gases. However, in specific cases, the approval of below-deck stowage depends on the particular type, mission, and arrangement of the ship. In such cases, these approved locations are shown on the ship’s plans. Compressed gases aboard all ships, except cargo ships, should be stowed in compartments designed for stowage of gas cylinders. In such cases, the following precautions must be observed: Take  the  necessary  steps  to  prevent  the m a x i m u m   t e m p e r a t u r e   o f   t h e   s t ow a g e compartment from exceeding 130F. When  provisions  are  made  for  mechanical ventilation, operate this ventilation according to the damage control classification assigned. The classification for closure of this system is ZEBRA (Z), CIRCLE WILLIAM [(W)], and WILLIAM (W). In  compartments  designated  for  stowing flammable or explosive gases, the installation of portable  electric  wiring  and  equipment  isn’t permitted. 19-14 Student Notes: