Balloon Conditioning As  a  result  of  exposure  to  relatively  low temperatures  or  extended  storage,  neoprene  balloons lose a portion of their elasticity through crystallization. Balloons   in   this   condition   will   burst   prematurely. Conditioning the balloons restores their elasticity and helps  ensure  higher  flights.  Balloon  conditioning should be done to all balloons more than 1 year old or that have been stored in cold temperatures. For Navy and  Marine  Corps  observations,  balloons  may  be conditioned  by  immersing  the  balloon  in  boiling  or nearly boiling water for 5 minutes. Balloon Inflation Proper  balloon  inflation  procedures  are  not published for the MRS system. The 100-gram and 300- gram balloons must be inflated so that the ascension rate keeps the MRS system active. Slower ascension rates may be interpreted as a leaking balloon, and the system will  terminate  the  sounding.  Faster  ascension  rates prevent accurate data sampling and may also result in automatic  sounding  termination  by  the  receiver.  The ideal ascension rate for a balloon is between 900 feet per minute and 1,000 feet per minute. INFLATION  GASES.—Helium    is    the    safest lighter-than-air gas for use in inflating meteorological balloons. It is inert and will cause no fire, explosion, or health problems. Hydrogen or natural gas can be used in  an  emergency  if  helium  is  not  available,  but  both gases   are   explosively   flammable   and   pose   serious safety  hazards.  Their  use  is  not  recommended.  The AN/TMQ-3  hydrogen  generator  set  has  been  used  at some remote upper-air sites to produce hydrogen gas locally. Two  types  of  helium  may  be  used  to  inflate balloons:   oil-free   and   oil-pumped   helium.   Oil-free helium  is  supplied  in  metal  compressed-gas  bottles  that are about 4.5-feet high; the bottles are painted gray, with the  top  portion  of  the  bottle  and  valve  cover  painted yellow or brown.    Since this gas is not hazardous to health, the bottle connection is a standard screw thread. Oil-pumped   helium,   however,   contains   more contaminants   than   oil-free   helium,   and   may   cause health  problems  ifbreathed.  These  cylinders  are  painted gray with an orange band around the cylinder, and the cylinder connection has a reverse-screw thread. The  standard  pressure-reducing  helium  regulator (fig. 1-5) is usually painted bright orange, and is used to regulate the flow of gas into the balloon. The regulator is attached to the oil-free helium bottles with an adaptor (on the chain). The indicator dial nearest the cylinder connection  indicates  total  pressure  in  the  helium cylinder  (normally  2,000  psi  when  full)  on  the  outer scale,  and  cubic  feet  of  helium  (220  cubic  feet  when full) on the inner scale. The second indicator dial shows the low-pressure flow to the regulator outlet. The low-pressure flow is adjusted  by  turning  the  T-handle  on  the  valve  body; turning  the  T-handle  clockwise  shuts  off  the  flow. Before the regulator is removed from the cylinder, the helium cylinder valve must be closed and the pressure bled  from  the  regulator.    A  low-pressure  hose  is  not supplied  with  the  regulator. Several  suitable  low- pressure  hoses  are  available  through  the  supply  system, but you may use a clear plastic, 3/8-inch-diameter hose that  is  lightweight  and  flexible.  Use  screw  clamps  to connect  the  hose  from  the  regulator  nipple  to  the inflation  nozzle.  Helium  flow  should  be  set  during inflation  at  about  15  psi  on  the  low-pressure  gauge. Inflating  balloons  at  higher  settings  will  inflate  the balloon  too  rapidly  and  stress  the  neoprene,  resulting  in premature balloon failure. Flow of gas into the balloon is controlled by the on/off valve on the weighted balloon nozzle. INFLATING   BALLOONS.—The ideal ascension rate for a 100-gram or 300-gram balloon is 900 to 1,000 feet per minute. This rate is achieved by inflating the balloon to neutral buoyancy (the balloon will neither rise nor sink on its own) while attached to an inflation  nozzle  weighted  from  approximately  600  to 1,000  grams  (1.3  to  2.2  pounds).  Before  release,  the weighted  nozzle  is  removed  and  the  250-gram  MRS RS-80 series rawinsonde instrument is attached to the balloon. A 100-gram balloon should have a free lift of about 600 to 800 grams, and a 300-gram balloon should have a free lift of between 800 to 1,000 grams. Figure l-5.—Standard pressure-reducing helium regulator. 1-7