Last post you read an excellent article from Chad Stroike of HIlti and this week I want to add a bit to it.
Imagine a room on fire. As the temperature mounts, the pressure inside the room will increase. We want to know that the integrity of the firestop system will be able to withstand the impact of this pressure increase. As the temperature grows metal elements through the walls and floors will expand and contract, twist and contort. They will be hot on one end and not on the other. Thin wires holding lights can snap, leaving the fixture to swing and slam into a rated wall. Furniture or heavy duct assemblies can crash into rated walls. We want to know that the firestop installed in these rated assemblies will have the integrity to withstand these potential hazards without becoming dislodged. This is one more reason for this hose stream test on top of everything Chad mentioned in his article. If you haven’t read it yet, you can get it here.
Something I found interesting when I first learned about the hose stream test, is that it is done half way through the test. This means that a wall or floor is taken off the furnace half way through the duration of the test and immediately subjected to the hose stream test. Picture a concrete floor with pipes or ducts that are red hot. Now picture a 30-PSI stream of water hitting the red-hot pipes and smoking hot concrete assembly. You can imagine the steam engulfing the room and shrouding your vision, the steam hissing in your ear and the smell of smoke choking you. Then, after this segment of the test is completed, you would walk to the “non-fire” side of the assembly and look for signs of water breaching the concrete floor. If there is light coming through the assembly or any sign of water that may have penetrated the floor, then the test assembly has failed. If the assembly passes, this is just one step in the process because the assembly must be burned for the entire duration. This means that many rated wall, rated floor or floor ceiling assemblies are likely tested twice; once for the full duration of the fire test and then often a second time for the hose stream test. This may not be the case for concrete or block assemblies because they don’t degrade as rapidly in a fire and may survive the hose stream test even after the full duration on the furnace. Certainly for gypsum assemblies, the fire side is basically sacrificial. It won’t last long in a fire test, so UL’s requirement is that the hose stream test is conducted at the half way mark of the test (but not more than 1 hour). This means that a 1-hour fire test will have a hose stream test conducted after 30 minutes. A 2-hour test will have a hose stream test conducted after 60 minutes, as would a 3 or 4 hour test.
If you ever get the opportunity to witness the hose stream test, you should. If you are at all a geek like me, you will appreciate the impact it makes on the test assembly.
Next week, we talk more about scenarios where the hose stream can cause a test sample to fail. Now that you have a better understanding of how firestop is tested, you can better understand why certain elements of the tested and listed details are critical to the performance of the assembly and critical elements to be inspected.