TM  10-3930-643-34 GENERAL  MAINTENANCE  PROCEDURES. 2-2. Personnel  Precautions. d. Ventilate. Do not operate engine or heater in a closed area unless area is properly ventilated. If you notice exhaust odors or exposure symptoms, immediately  ventilate  the  area. e. Handling Heavy Items. Properly  support  heavy  items  before  removing. Keep clear of suspended items. Use  sufficient  number  of  personnel  to  maintain control of item. If item begins to fall; let it fall. Ensure that hoist or hydraulic floor jack has sufficient capacity to do the job and provide an ample safety margin. f. Prevent  Accidental  Movement. Never leave vehicle unattended while the engine is running. Observe all pre-conditions before performing maintenance. g. Use Sturdy Supports. Do not climb on tires. Use  mounted  steps  and ladders when climbing onto vehicle. If needed, use a sturdy step ladder to perform maintenance on equipment not safely within reach. 2-3. Vehicle Precautions. Observe all cautions listed in this manual. The word CAUTION appears in this manual to alert you to conditions that could cause damage to the vehicle and its components. Cautions are listed before the procedure to which they apply. Other  general  vehicle  precautions  include: a. During  service  maintenance  turn  master  disconnect  switch  off  to  prevent damage to the electrical system. b. Disconnect  battery  ground  when  required. c. Use a hoist or hydraulic floor jack of sufficient capacity to remove and support heavy items. 2-3