Why Every Project Should Have a No-Fly Zone

Have you ever run into a problem on a jobsite that you can only fix if you knew about the issue earlier? This article may help you avoid a common problem and understand why acting as early as pre-con, reduces liability.
Let’s paint a picture of the problem for you. Then we will explain some of the reasons this common field application is a code violation. Let’s establish the context before diving into the details.

Let’s say we’re building a high-rise hotel. The architect wants the ceilings to be as high as possible with the building as short as possible. This means, particularly in the corridors, ductwork, cables, conduits and sprinkler pipes will all be running high and tight; as close to the underside of the floor as possible.

When you are looking at smaller penetrations such as sprinkler pipes, small conduits and cables, they are often secured with straps shot to the underside of the deck, all but promising that the penetration will land in the head of wall joint. The physical installation of the firestop won’t seem like much of a challenge, but the ducts, even small, ones will be.

Let’s say the duct is small, maybe 4″ high by 8″ wide. When the drywall is installed, there is access to firestop down the left side, across the bottom and up the right side. The firestop may get pumped into that top space about an inch on either side. That will leave, let’s say, 6″ of a gap at the top of the duct that can be firestopped.

Bruce Johnson of Underwriters Laboratories (UL) informed us in a piece by Katie Moore of WWLTV, “Even a smallest void that’s not properly protected with proper firestopping almost acts like a blow torch…fire rapidly spreads…beyond that compartment” if this happens in every unit, then regardless of which room the fire is in, this is what could happen.

The pressure build up in the room will push the heat and smoke to the upper areas of the room. The pressure will force the smoke into the corridor where it will mix with the cool air filling the entire corridor and obscuring visibility slowing the speed with which people can exit a building.

According to a UL demonstration a room filled with modern furniture could reach flashover in 3 minutes and 40 seconds (the temperature where everything in the room gets hot enough to ignite). This could be faster or slower depending on the size of the room and any number of other variables, but if you watch that video, you may be surprised as you watch just how fast this happens.

So, the duct is a clear issue. Let’s talk about what’s wrong with those smaller cable conduits and sprinkler pipes. There are four issues: codes, temperature, pressure and structure.

Codes

To understand this, we must discuss how the fire test standards impact the building code. My friend Doug Evans once said something that really nails this, “If you don’t understand the standards, you don’t understand the codes.” This is SO TRUE. Let’s look at why. “715.3 Fire Test Criteria Fire resistant joint systems shall be tested in accordance with the requirements of either ASTM E1966 or UL2079.”

If you don’t understand these standards and the pass/fail criteria, then it’s going to be a challenge to understand why this scenario of having penetrations located in the head of wall joint is not only a code violation, but a liability for any project.

When these test standards are conducted, they build a wall, they allow time to cure. Then they install firestop at the head of the wall joint, allowing that time to cure and its read for the burn test. They may subject the assembly to movement testing, but that’s a story for another time, we’ll get there eventually, just not today. There are lots of things that go into this test standard but the two that we’re going to address here are related to temperature and pressure.

Temperature

When the assembly is prepared to go on the furnace, there are a handful of thermocouples required in specific locations, including on the surface of the firestop material at the joint. If the temperature of a single thermocouple exceeds 325°F or the average exceeds 250°F then this fire-rated joint assembly would be considered a failure and would not receive a listing.

Aluminum and copper are probably what will be inside your MC cable. Both are excellent conductors, which is why they are so commonly used in electrical applications. That also means they will pull heat to the non-fire side of the assembly rapidly. Now that you understand this basic pass/fail requirement of the fire test standards, it’s easy to see why this application would fail to meet the requirements of the code. They simply failed to meet the requirements of the test standard.

Pressure

Another requirement of ASTM E 1966 and UL 2079 is something that’s unique to the fire test standards in the United States. When we test a gypsum wall and when we test a head of wall firestop joint in a gypsum wall, they will perform the test twice. The first time will be to identify whether the assembly can prevent the passage of fire. The second time will identify whether the assembly can pass the hose stream test.

At the halfway mark on a one- or two-hour test, they will pull the assembly off the furnace and apply a hose stream test that has 30 pounds of pressure. The stream of water will be waived back-and-forth across the assembly and if there is a thorough projection of water, this assembly will be considered a failure.

Field Assembly/Structure

Now that you understand these three things, let’s talk about the impact on the field condition we’ve created when we have a penetration through our head of wall firestop joint.

1. When the head of wall joint is tested, it will have a solid piece of framing at the joint. If there is a penetration in this location, the framing is going to be cut. Do you think the hose stream may create different results without the framing member ON BOTH SIDES of the rated joint?
2. Clearly the cable, conduit pipe or duct will not be able to prevent heat from passing through the joint location, so clearly this field application cannot meet the requirements of the fire test standard, which means you can’t meet the code. The solution most people choose is to ask the firestop manufacturer for an engineering judgement (EJ).
   

Question: What if you get an EJ from a firestop manufacturer?

Answer: As explained, one of the requirements of the fire test standards is that the assembly does not allow thermal transfer for the same time it can prevent the passage of flame. Sometimes an EJ has a line somewhere on the document that says, “T rating may not meet the F rating.” That line is telling you that the application won’t meet code, but the manufacturer is giving you a document just in case anyone approves it.

3 .When there is structural movement in the building, this penetration is likely to reduce the movement that the joint can tolerate without damaging the firestop solution.

Simple Solution

Mandate a no-fly zone. No trades allowed penetration in the first X inches below the head of wall joint. Join us for the next discussion where I will explain my favorite thing to add to a no-fly zone.

A firestop expert since 1999, Sharron Halpert has supported $22B+ in major projects worldwide. As head of Halpert Life Safety Consulting, an ASTM voting member and international trainer, she provides specialized inspections, consulting and SAFETY Act protocol deployment.