Volkswagen Passat 1995 Official Factory Repair Manual page 4104

A/C refrigerant system, notes
http://ebahn.bentleypublishers.com/vw/servlet/Display?action=Goto&type=repair&id=VW.B4.HA01.87.1
Flammability
R-134a refrigerant is not flammable. In fact, it
tends to inhibit combustion and has a fire
extinguishing effect. However, a flame or glowing
hot surface, as well as ultraviolet light (from
electric welding), will decompose the refrigerant
into poisonous gases (hydrogen fluoride,
carbonyl fluoride and fluorine). These gases give
adequate warning of their presence since they
cause irritation of the mucous membrane
(throat).
R-134a can become flammable at pressures
above ambient pressure in conjunction with air
concentrations greater than 60% by volume.
Refrigerant containers
DO NOT exceed maximum rated capacity of
refrigerant containers. Never fill a container to
more than 60% of its gross weight rating (for
example, 18 lb in a 30 lb container.)
Without sufficient room for expansion of R-134a
(gas cushion), the container could explode when
the temperature rises causing serious injury.
Leak detection
Use halogen leak detector Hitec HI400A-TEL, or
equivalent, to check for R-134a system leaks.
This tool can also be used to detect leaks in R-12
systems. Many currently available R-12 leak
detectors cannot detect R-134a refrigerant
leaks.
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