be forced into the room from, between the bell and tank. The bell is guided
in its rise and fall by vertical rods so that it will not wedge at any
point in its travel.

A condensing chamber to receive the water which condenses from the
acetylene gas in the holder is usually placed under this part and is
provided with a drain so that this water of condensation may be easily
removed.

_Filtering._--A small chamber containing some closely packed but
porous material such as felt is placed in the pipe leading to the torch
lines. As the acetylene gas passes through this filter the particles of
lime dust and other impurities are extracted from it so that danger of
clogging the torch openings is avoided as much as possible.

The gas is also filtered to a large extent by its passage through the water
in the generating chamber, this filtering or "scrubbing" often being
facilitated by the form of piping through which the gas must pass from the
generating chamber into the holder. If the gas passes out of a number of
small openings when going into the holder the small bubbles give a better
washing than large ones would.

_Piping._--Connections from generators to service pipes should
preferably be made with right and left couplings or long thread nipples
with lock nuts. If unions are used, they should be of a type that does not
require gaskets. The piping should be carried and supported so that any
moisture condensing in the lines will drain back toward the generator and
where low points occur they should be drained through tees leading into
drip cups which are permanently closed with screw caps or plugs. No pet
cocks should be used for this purpose.