www.pilotballoon.com "the pilot balloon web resource" 

Up Hydrogen Genarator Hydrogen & Nozzles US 10 Gram Nozzle ML-373/GM U.K.Met Weights Hydrogen Safety Aero Balance Helium Inflation Equipment

Pilot Balloon Fillers and Weight Sets

Pilot balloons are filled with a lighter than air gas.  Hydrogen or Helium are used most always.  (I have heard a rumor of use of Natural Gas usage in South America but this in unconfirmed)

Hydrogen offers the greatest lift per unit volume and can be generated on site with the use of a hydrogen generator and a calcium hydride charge.  Hydrogen is a flammable and explosive gas.  Comprehensive safety precautions are required for use of pilot balloons to avoid potentially serious accidents.

Helium has less lift than hydrogen.  Helium is much more safe to deal with, totally non-reactive and other than its ability to displace breathable air, and the fact that any pressurized gas cylinder presents some hazards it is inherently safe.  Due to the inert nature of helium no compounds contain it and hence it cannot be "generated" on site like hydrogen can. 

Fillers and weights are made to accommodate 4 balloon types.  10 gram balloons (usually used to determine cloud height, 20 gram balloons (cloud height and low wind speed or low altitude work, not that common), 30 gram balloons (the standard historical pilot balloon size) and 100 gram balloons (higher ascent rate, for use in high winds or where higher altitude measurements are required).  

Balloons of 300 grams or greater are sounding balloons they have a much larger neck size than the 30 and 100 gram balloons do.  These balloons are for carrying radiosondes (instrument packages) aloft.

Hydrogen generator set.  This is an American hydrogen generator.  The page also includes an illustration of its use.

Hydrogen inflation equipment, includes a hydrogen generator, nozzles and weights to achieve specified free lift and ascent rates.

Helium Inflation Equipment, includes a helium gas regulator, high pressure hose, hand valve, quick release gas fittings, 30/100 gram balloon nozzle, 10 gram balloon nozzle.  

Aero-1945-USN, Universal Balloon Balance by Wallance and Tierman Products. A nozzle/weight system supporting a number of balloon weights and ascent rates used with hydrogen.

10gm Pilot Balloon Nozzle, U.S. Pattern for Helium daytime use only.  10 gram balloons are often called ceiling balloons as a result of their common historical use for measuring cloud ceilings.  

ML-373/GM Nozzle and Weight Set used by U.S. Army and Marine Artillery Units is photographed here.  It is also illustrated in the hydrogen inflation equipment section above. 

UK Meteorological Office Pilot Balloon Weight Sets and fillers were made for use with hydrogen only.  Information and weights are not supplied for inflation with helium.  They will inflate balloons with helium, just not produce Met Office standard ascent rates.