The Rigors of Firestop Tests Part 1

This post originated from Adhesives.org in 2018/19 as paid content, belonging to the organization. We are reposting it here because the original is no longer available online, and we want to share this valuable information.

We’ve extensively discussed firestop tests and their methodologies, but we haven’t explored their achievable ratings in depth. I’m referring not to hourly ratings but to something distinct. Firestop assemblies undergo testing for ratings such as F, T, L, and W. Some of these are mandatory under code, while others are optional. Today’s blog focuses on the L rating—its definition, when it’s mandatory, and how to ensure compliance. We will get into the others shortly, but if you can’t wait to learn what they are, you can go here.

Let’s dig into these L–ratings. L-ratings quantify the airflow (including cold smoke) that penetrates through a passage, measured in cubic feet per minute. These ratings are evaluated under a differential pressure of 0.30 inches water column (75 Pa) at both 75 ^oF and 400 ^oF.  Similar to the test for movement criteria that we talked about in this post (http://www.adhesives.org/resources/knowledge-center/aggregate-single/fireproofing-firestopping-and-fireblocking-(part-2-of-4.)) for the joint assemblies.  It precedes the burn test in the furnace, applicable to both joint assemblies and penetrations.

The L rating is mandated by the 2015 IBC and earlier code cycles. Section 714.4.4 stipulates that penetrations in smoke barriers must deploy UL 1479-approved through penetration firestop systems, tested for air leakage. The L rating must not exceed:

This means that if you are a firestop installer or inspector, you need to know where the smoke barriers are in the building. Ensuring submitted firestop details meet L rating requirements is essential. If you are an architect responsible for reviewing firestop tests submittals you need to ensure that the smoke barrier walls have all the firestop details they need and that needs to include L ratings. It also means that if you are a manufacturer this L rating will be a requirement for your firestop details.    

When reviewing firestop test submittals, note the UL listed detail above lacks an L rating, while the system below has one.  Below is a system that has an L rating.  Please note it says see Item 1B.  This is potentially one more step for the installer and the inspector to follow through on during their scope of work.   

While we addressed L ratings as a potential code requirement, we didn’t cover scenarios where architects specify them outside of code requirements, such as hospitals, data centers, condos, and apartments. A few examples could be in hospitals, data centers and even condominiums and apartments.   

An architect may specify L ratings in these types of occupancies for very different reasons. Let’s take apartments and condominiums for our first example.  The biggest complaints are noise and smells that make their way from one unit to another. L ratings can help reduce both of these complaints. 

Hospitals have this concern with what they call nosocomial infection. Properly firestop buildings can reduce the rate of nosocomial infection and this happens by reducing the air leakage.

Data centers are a concern because when you look at all the plastics that are in a data center, lets take PVC for an example.  When that burns you get airborne particles of polyvinylchloride. When the chlorine combines with the water in the atmosphere you suddenly have airborne hydrochloric acid that gets into the electronics and renders them useless.  Limiting airflow minimizes damage from smoke migration.

Hopefully, this helps you understand the importance of this little know firestop tests. If you have any questions about this code requirement, you are welcome to reach out to the author. 

Additional resources are:

Thanks for your time and keep learning about this industry, you never know when it could save your life.