MAPP gas has a detectable odor at 100 ppm or at a
concentration 1/340 of its lower explosive limit.
Small fuel-gas systems may leak 1 or 1 1/2 pounds of
fuel or more in an S-hour shift; bulk systems leak even
more. Fuel-gas leaks are often difficult to find and
oftentimes go unnoticed; however, a MAPP-gas leak is
easy to detect and can be repaired before it becomes
MAPP toxicity is rated very slight, but high con-
centrations (5,000 ppm) may have an anesthetic effect.
Local eye or skin contact with MAPP-gas vapor causes
no adverse effect. The LIQUID FUEL MAY CAUSE
DANGEROUS FROSTLIKE BURNS because of the
temperature at which MAPP gas must be stored.
OXYGEN.-Oxygen is a colorless, tasteless, and
odorless gas slightly heavier than air. It is not
flammable but supports combustion with other
elements. In its free state, oxygen is one of the most
common elements. Rusting of ferrous (containing
iron) metals, discoloration of copper, and corrosion of
aluminum are all due to the action of atmospheric
oxygen. This action is called oxidation.
When oxygen is supplied for use in oxyacetylene
welding, oxygen is contained in seamless steel
cylinders. A typical oxygen cylinder is shown in figure
3-52. Oxygen cylinders are made in several sizes;
however, you will find the size most often used in
welding and cutting is the 200-cubic-foot capacity
cylinder. It is 9 1/8 inches in diameter and weighs
about 145 pounds. This cylinder is charged to a
pressure of 2,000 psi at a room temperature of 63°F
You can tell the amount of oxygen in a
compressed-gas cylinder by reading the volume scale
on the high-pressure gauge attached to the regulator.
REGULATORS. The gas pressure in a cylinder
must be reduced to a suitable working pressure before
it can be used. This pressure is reduced by a regulator
or reducing valve. Regulators that control the flow of
gas from the cylinder are either single stage or double
stage. Single-stage regulators reduce the pressure of
the gas in one step, while two-stage regulators perform
the same work in two steps or stages. Generally, less
adjustment is necessary when two-stage regulators are
Figure 3-53 shows two SINGLE-STAGE
regulators: one for acetylene and one for oxygen. The
Figure 3-52.Typical oxygen cylinder.
Figure 3-53.Single-stage regulator.