thermal shock and force of applying a cold, high-pressure
stream of water to a red-hot assembly is a good measure
of system integrity.
To pass the hose stream test, the firestop system must
prevent the passage of water to the unexposed side. It is
important to remember that a building fire is a dynamic
event. As pressure levels change and heat becomes more
intense, surrounding structures and elements can fail,
thereby stressing the firestop. A good measurement
of system integrity is established by the thermal shock
of the cold high-pressure water stream to the red-hot
March/April 2019 I 59
FIGURE 4: The hose stream test immediately follows the fire test.
In the Figure 3 scenario, the assembly is anchored
to the test furnace. During the testing process, the
firestop collars expand through a process called
intumescence (i.e., heat applied to the firestop material
that causes it to expand rapidly). In so doing, they close
off the openings and prevent the fire from spreading.
Intumescent products are common in the industry,
particularly well-suited for combustible materials, and also
frequently used on noncombustible materials as well.
The hose stream test (Figure 4) immediately follows
the fire test and is designed to evaluate the structural
integrity of the assembly. This is by far the most difficult
segment of the test to pass. The red-hot assembly is
blasted with a stream of cold water from a 64 mm
(2-1/2 in.) diameter hose discharged at high pressure.
Not only does the assembly need to withstand the force
of the water pressure, it also needs to withstand the
strong internal forces developed from the thermal shock
of rapid cooling. UL 1479 prescribes the pressure and
duration of the hose-stream exposure, which depends
on the hourly rating being tested and the size of the
assembly. Firefighters should particularly be aware of the
hose stream test as it gives an indication of whether
a structure will withstand the back-draft effect. The
Aluminum cable conductors
typically melt at 649°C (1,200°F)
and many plastics ignite at
temperatures significantly below
538°C (1,000°F), which is within
two or three minutes of the
start of a fire!