The best way to protect personnel against these contaminants is through the use of engineering controls such as local exhaust ventilation. When these controls are not practical or do not provide sufficient protection, appropriate respirators are required to assure the protection of personnel. How often have personnel used surgical masks when a respirator was required for painting, chipping, or grinding? That practice should be stopped. Surgical masks are designed to stop only the flow of oral discharges. They are not designed to impede the flow of organic vapors or metal fumes. Organic vapors and fumes pass through the mask and into the wearer’s respiratory system. Three  general  types  of  respirators  are authorized: Air-purifying  respirator.  This  respirator removes contaminants by filtering or adsorbing them  as  the  air  passes  through  a  cartridge. (Adequate oxygen must be present in all spaces where these respirators are used.) Supplied-air (or air-line) respirator. This respirator  is  used  when  there  is  insufficient oxygen, the contaminant has no odor, or when the contaminant is of such a high concentration or toxicity that a cartridge filter is inadequate. Self-contained breathing apparatus (SCBA). This apparatus allows the user complete inde- pendence from a fixed source of air and offers the greatest degree of protection, but it is also the most  complex. WARNING The OBA and emergency escape breathing device (EEBD) are to be used only in damage  control  and  emergency  escape situations, respectively. Respirator cartridges and gas mask canisters are color-coded as to the type of contaminant they provide protection against. Respirator and cartridge selection guidance and information is provided in OPNAVINST 5100.23B, NAVOSH Program Manual Heat Stress Program Heat stress may occur in engineering spaces, laundries, and many other work spaces in the Navy. In many cases, it is the result of inadequate or clogged ventilation systems, damaged or missing thermal insulation, or excessive steam or water leaks. Heat stress is defined as any combination of air temperatures, thermal radiation, humidity, airflow, and work load that may stress the body as it attempts to regulate body temperature. Heat stress becomes excessive when the body cannot adjust to the temperature of its environment. That results in an increase in body temperature. This condition  can  readily  produce  fatigue,  severe headaches, nausea, and poor physical and mental performance. As the body’s temperature continues to increase because of prolonged exposure, heat exhaustion or heatstroke may occur. Severe impairment of the body’s temperature-regulating ability also may occur. Heat stress can be life- threatening if not immediately and properly treated. Recognizing heat stress symptoms and obtaining prompt medical attention for affected personnel is an all-hands responsibility, but is of special concern to supervisors. Further  information  and  guidance  on  the Navy  Heat  Stress  Program  is  contained  in OPNAVINST  5100.20,  Shipboard  Heat  Stress Control  and  Personnel  Protection. Electrical Safety Whatever your job in the Navy, chances are great that you and your personnel will be working with or near electrical or electronic equipment during the normal workday. Persons working around  electric  circuits  and  equipment  must always observe safety precautions to avoid injury from electric shock and short circuits. Detailed safety precautions are contained in the Naval Ships’ Technical Manual (NSTM), chapter 300, and the Electronics Installation and Maintenance Book  (EIMB),  NAVSEA  SE000-00-EIM-100, section 3. They may also be found in type- command instructions. For purposes of this discussion, the terms  electrical  and electronic should be considered interchangeable. The danger of shock from 220-volt or 450-volt ac service is well recognized by operating person- nel. Relatively few reports of serious shock are received from these voltages despite their wide- spread use. On the other hand, a number of fatalities have occurred because of contact with 115-volt circuits. Low voltage (115 volts and below) is very dangerous, despite a fairly widespread but totally unfounded belief to the contrary. Contact with low voltage can cause 6-6