_c. Use of fuel in training._ When using fuel in training, select or prepare a practice field of fire which provides at least 125 yards for range and 30 yards for spread. If the field contains dry grass, brush, or other flammable material, a fire-fighting squad should be available with equipment and source of water. Assistants and observers should stay well behind the firer because of danger from wind shifts. See Paragraph 40 for additional precautions. 16. CHARGING, FILLING, AND SERVICING. Before use on missions or for training, flame throwers must be charged, filled, and serviced. Charging with compressed air or compressed nitrogen is described in Paragraphs 32 and 33; filling with fuel in Paragraphs 34 through 40; and servicing in Paragraphs 50 through 56. Test for pressure. (Par 53 _d_) 17. CONNECTING TANK GROUP AND GUN GROUP. If a charged and filled tank group has been brought up to replace an emptied one: _a._ Place the new tank group on the ground with the tank coupling on top. If the filling is thickened fuel, allow the tank group to rest in this position for from 1 to 2 minutes. _b._ Remove coupling plug from new tank group and disconnect gun group from emptied tank group. Place unthreaded end of fuel hose in tank coupling and lock in place. (Par 70) _c._ Lock the coupling plug in the emptied tank group. 18. LOADING WITH IGNITION CYLINDER. _a. General._ Just before the start of a mission, load an unused ignition cylinder into the ignition head. (M1 and E1 ignition cylinders are identical and may be used interchangeably.) Cylinders are packed two to a can. Do not open cans until ready to load for a mission. The second cylinder in the can should be used in another flame thrower on the same mission or as soon as possible after opening the can. Partly used cylinders may be employed in training. _b. Precautions._ Care must be taken, whenever cylinders are handled, to avoid any blows or pressure against the metal match ends. (Fig 13) Face, hands, and other parts of the body should never be exposed to front of cylinder or front of gun. [Illustration: Fig 13. Ignition cylinder before use.] _c. Procedure._ Loading procedure is as follows: (1) Unscrew and remove ignition shield. (Fig 14) (2) Place ignition cylinder on end of barrel (Fig 15), being careful not to grasp cylinder by its ends. (3) Raise nozzle end of gun so cylinder slides down against the spring case of the ignition head. (Fig 16) If necessary, rotate cylinder so it slips down all the way. Do not force cylinder into place as forcing may prematurely ignite it. (4) Rotate spring case and ignition cylinder clockwise as far as they turn freely. (5) Place ignition shield over cylinder. Engage the slot in the shield on the spring-case pin. (6) Turn shield, screwing it onto ignition-head body. Make sure the threads engage during the first turn of the shield. When the slot on the shield engages the latch on the ignition head (Fig 17), the gun is loaded.