entered a declared safe space, periodic tests are made to determine that it is still safe. Upon the detection of an unsafe condition, an order must be given for all personnel to evacuate the space. Because  a  space  cannot  be  guaranteed  to  remain safe, you should be aware of the symptoms of bad air. Symptoms of bad air include the following: Labored breathing Excessive fatigue from slight exertion Headache Dizziness If you feel any of these symptoms, warn others and get to fresh air immediately. A more dangerous situation exists if a compartment has no, or very little, oxygen. If this happens, a person can  lose  consciousness  almost  immediately  without warning. If such an incident occurs while you are in an area, do not enter the space without wearing an OBA or air-line mask; otherwise, you will become a casualty. Always summon (call for) help before making a rescue attempt. Also, have a person stationed at the entrance to maintain  communications  while  watching  to  see  that you are not overcome. TYPES OF SOLVENTS As you have already learned, the Navy uses many types of solvents for many cleaning assignments. You also know that many of these solvents are highly toxic and some are highly flammable. Take special care when using many of these solvents; make sure you store them in  cool,  dry  areas.  Material  Safety  Data  Sheets (MSDSs) list the storage requirements for solvents. You should refer to the MSDS for solvents you are using. Most  cleaning  solvents  contain  toxic  substances. These substances can cause injuries if they are inhaled, absorbed by the skin, or ingested. All toxic materials must  be  handled  carefully  to  prevent  injury.  Many  of them have additional hazards, such as flammability. The following  paragraphs  contain  information  about general  categories  of  toxic  cleaning  solvents.  If  you have any questions about the solvent you are going to use,  check  the  Maintenance  Requirement  Cards (MRCs) for the task or ask your supervisor. The three types of solvents covered in this section are  chlorinated  cleaning  solvents,  organic  cleaning solvents, and fluorocarbon refrigerants and solvents. Chlorinated Cleaning Solvents Chlorinated cleaning solvents can be highly toxic if used  improperly.  They  may  be  irritating  to  skin  and toxic  if  ingested.  In  confined  spaces,  in  spaces  with inadequate ventilation, or when the vapor concentration is increased by heating, toxic vapors may cause damage to  the  lungs,  eyes,  and  nervous  system.  Solvents decompose  at  high  temperatures  and  produce  gases more toxic than the solvents themselves. Solvents react with  alkalies,  oxidizers,  and  powdered  metals  to produce toxic gases. Common types of chlorinated cleaning solvents are trichloroethane  (inhibited  methyl  chloroform), trichloroethylene,  tetrachloroethane,  and  tetra- chloroethylene  (perchloroethylene,  dry-cleaning solvent). Because of the extreme dangers involved, the Navy severely restricts the use of these solvents. You should observe the following precautions when working with chlorinated cleaning solvents: Never  stow  chlorinated  cleaning  solvents  near heat sources or open flames. Don’t  allow  them  to  come  in  contact  with  hot surfaces. Make sure stowage areas are well ventilated and monitored  regularly  by  the  gas  free  engineer. Don’t  stow  these  solvents  near  incompatible materials.  (NOTE:  Incompatible  materials include   strong   alkalies,   such   as   sodium hydroxide;   oxidizers,   such   as   calcium hypochlorite  and  sodium  nitrate;  or  powdered metals, such as aluminum.) When handling chlorinated cleaning solvents, wear the following personal protective equipment (PPE): Neoprene gloves 18-8 Student Notes: