Understanding Firestopping for Fire Alarm Technicians
Mitchell Tai, B.Sc., ITC, BCIN Vitalis Engineering
As fire alarm technicians, we are relied upon as experts in performing installation, programming, inspection and verification of fire alarm systems. However, we are frequently requested to perform other tasks not directly associated with the fire alarm system, but are related to the work we do. Firestopping is such a task.
There is a lot of misunderstanding on “Firestopping”. It’s a term that is usually an afterthought near the end of a project when the fire alarm wiring has been pulled, or when all sprinkler pipes have been installed. Usually, the responsibility falls on the apprentice electrician or fitter. They are handed a tube of caulking or sealant and instructed to go around filling up any holes in the wall that they can find. It’s a menial task that seems simple enough. However, due to the perceived simplicity of the task, it is commonplace for minimal effort to be put in, or for firestopping to be overlooked altogether.
What is firestopping?
As we know in the fire protection industry, the walls, ceilings, and floors of our buildings are often more than just spatial partitions. More often than not, they are fire separations that provide a fire resistance rating to prevent the spread of fire and smoke from one side of the wall to the other. For a fire separation to perform its duty, a key term cannot be overlooked: continuity. A fire separation is only as strong as its weakest point; the effectiveness of the fire separation depends on the continuity of the fire separation assembly from floor to ceiling, wall to wall. Any hole or opening in the fire separation effectively nullifies the fire resistance rating of the entire assembly, allowing fire to spread quickly and easily to the other side of the separation. These holes in the fire separation are called fire penetrations, and any objects passing through these holes are called penetrants. It’s a very self-explanatory name as these holes in the wall would allow fire and smoke to penetrate the otherwise rated separation. Firestopping is an engineered method of sealing these fire penetrations to provide continuity of the integrity of the fire separation. The goal of firestopping is to provide a fire resistance rating that is equal to or better than the existing rating of the fire separation. With that in mind, we can delve deeper into the fascinating world of firestop assembly prescriptions.
Firestopping is not a “one size fits all” solution.
If we think about it logically, penetrations and penetrants can come in greatly varying sizes, shapes, and number. If we take the example of the apprentice going around with a tube of caulking, it’s entirely possible that they may come across a massive penetration which would need multiple tubes of caulking or sealant to fill. It would not only be inefficient; it would be nearly impossible to fill a wall penetration with a sealant, and if they did manage to fill it, the entire penetration would have no recognized rating. This is one of the most common misconceptions about firestopping. Firestopping is engineered as a complete assembly. This takes into account many different parameters, making each firestop assembly unique and prescribed for certain use cases. With all parameters taken into account, the firestop assembly is then tested by ULC to a specific standard, then provided with a ULC rating based on how long it can prevent fire, heat, and smoke from penetrating to the other side of the separation.
How do the ratings work?
Firestop assemblies are provided with 3 main ratings to take into account. F ratings are the most straightforward. This is simply how long the firestop assembly can prevent the passage of fire from one side of the assembly to the other. When choosing a firestop assembly to fill a penetration, this is usually the most important rating to consider, as we need to ensure the F rating is equal to or greater than the rating of the fire separation that we are trying to protect. In addition to the F rating, there is also a slightly less common rating called the T rating. This rating has to do with the passage of heat from one side of the assembly to the other. The T rating is the time it takes for the temperature to rise 181oC above ambient temperature on the unexposed side of the separation. To put it in simpler terms, it measures how long it would take for a fire on one side of the fire separation to increase the temperature on the other side of the fire separation by 181oC, or 325oF. Finally, there is the least common rating, the H rating. This is a measure of the amount of time the firestop assembly can be exposed to fire and still have enough structural integrity to withstand a hose stream. This is the hardest rating to obtain, and most firestop assemblies that we see will have a much lower H rating than F or T rating. Other than F, T and H ratings, firestop assemblies can be assigned combination ratings, including: FT, FH, or even FTH ratings. This simply means that the firestop assembly obtained the same F, T and H ratings. The required ratings depend on the location of the fire separation you are trying to firestop. F ratings are the very basis of firestopping. The requirements for T ratings and H ratings can vary depending on Code requirements, or even contractual obligations. Ratings will be a key factor in determining which firestop rating to prescribe.
How do we prescribe firestop assemblies?
As previously mentioned, there is no one-size-fits-all solution for firestopping. There are some firestop assemblies that can be used for a wide variety of penetrations, but each firestop assembly has its parameters that need to be met before the assembly can be used. Let’s take a look at some of the key parameters that we have to take into account when choosing a firestop assembly for our penetration.
1. Rating
As previously discussed, the F rating of the firestop assembly should always be greater than or equal to the fire resistance rating of the fire separation that we are trying to apply it to. This is to provide the continuity of the firestop as we previously mentioned. Since the fire separation is only as strong as its weakest link, we need the firestop assembly to be as strong as the fire separation to maintain its integrity across the penetration.
2. Fire Separation Construction
As we know, walls can be made of many different types of materials that can range from non-combustible masonry or concrete walls, to gypsum board on steel or wood studs. Each firestop assembly is designed with a specific wall construction in mind. A firestop assembly that would adhere to a masonry or concrete wall may not properly set in a framed wall, or vice versa. Along with the combustibility of the separation, we also need to take into account the thickness of the separation, as well as the type of separation. Separations can be categorized into wall separations, and floor separations. The major difference between the firestopping for these two separations is that firestop assemblies for wall separations are rated from both sides, and require structural integrity on both sides. There are certain floor firestop assemblies that only require sealant on the topside of the separation (i.e. on the floor) but not on the bottom side of the separation (i.e. the ceiling on the storey below).
3. Penetration Size
When we talk about the size of a penetration, we are referring to the actual size of the hole itself. This can be measured in a variety of ways, but the two most common ways are to describe the hole as a circular opening with a certain diameter of space, and the second way would be to describe the hole as a rectangle with a width and height dimension. Firestop assemblies always have a maximum size for the hole. This is because certain materials are just not meant to fill massive holes. In our previous example, a fluid sealant physically would not be able to fill a large hole without the addition of some sort of aggregate or other component.
4. Penetrant Parameters
Another major parameter to factor into the equation is the penetrant itself. While this may seem simple, the penetrant itself can also have many different types, sizes, and shapes. Firestop assemblies are usually designed for certain types of penetrants. For example, the most common penetrant type are pipes and conduits. Pipes themselves can be made of different materials, be different sizes, and have different material thickness. Other than pipes and conduits, penetrants could also be ducts, or cables; each one of these have sub-parameters, similar to how pipes could be further divided into sub-groups.
5. Annular Space
This may be a new term for those not familiar with firestopping. As we discussed above, a penetration is a hole in fire separation. If we imagine the cross section of the hole as a circle with a certain diameter, and penetrant as another circle with a smaller diameter, the space between the outer diameter of the penetrant to the inner diameter of the penetration is called the annular space. Each firestop assembly is designed with a minimum and maximum annular space in mind. Some assemblies require a minimum annular space because the materials used have a minimum thickness. Other assemblies allow “point contact”, which is when the penetrant and penetration are physically making contact. This is to accommodate the different types of materials used in firestop assemblies, all of which may require different minimum and/or maximum thicknesses to obtain the correct rating.
Putting it all together
Each fire penetration is a combination of these elements and parameters. Each one of these parameters should be satisfied in order to properly firestop any given fire penetration. If even one of these parameters is not met, the firestop assembly is not rated for that penetration. After finding the right assembly, it should be noted that each firestop assembly also has proper installation instructions that need to be followed in order to obtain the correct rating. For example, one of the most common assemblies consists of mineral wool batting with sealant covering it to provided structural integrity. However, the sealant application is usually specified depending on the type of sealant used in the assembly. Self-leveling sealant only needs to be poured onto the top surface of the mineral wool batting and left to dry. There are also sealants that need to be caulked onto the mineral wool from above and below in order to obtain the proper rating. Another example would be the specific compression ration of the mineral wool batting. All firestop assemblies will have a specific minimum compression ration for the mineral wool to be installed. If the mineral wool does not reach the minimum density, the rating cannot be attained. It is of utmost importance that installation instructions are followed.
What if no firestop assembly fits the exact penetration?
Let’s say you have a fire penetration in a masonry floor. The penetrant is two individual copper pipes with an annular space of 1/2” between the two pipes, and 3” to the penetration opening. The required separation is a 2-hour FT rating. After searching for hours and hours, there just isn’t a firestop assembly that satisfies these exact conditions. It’s either that the required annular space between the two penetrants is too large, or the T rating is not high enough, or the firestop was designed for a black steel pipe rather than a copper one. All hope seems lost. However, there are a few options we can choose:
- A) Use one of the firestop assemblies that best fits the fire penetration
- B) Use “fire blocking foam” (only $12 a can at your local hardware store)
- C) Use a generic firestop assembly, but shove in as much mineral wool batting and sealant as you possibly can and pray for the proper rating.
- D) Combine two different firestop assemblies so each assembly covers the other assembly’s shortcomings
If you chose answer A or D, you’d be partially correct. If you chose answer B, read this article again from the beginning. The use of fire foam in lieu of a proper firestop assembly is one of the most common deficiencies that can be seen in buildings all across Canada. It’s very conspicuous to see the telltale orange-yellow foam sticking out of a fire penetration like a sore thumb. These foams are NOT rated for firestopping. If you read the fine print closely, the cans actually say that these foams are flammable, and could release toxic smoke when burning. Moreover, the fine print also clearly states that this product is for residential fireblocking (i.e. not firestopping) only. Not only are these not doing the job of a proper firestop assembly, they are making it worse by releasing toxic fumes.
What is the correct method?
The reason why answers A or D are partially correct is because that is essentially what needs to happen in order to properly firestop the penetration. However, this is not up to you to figure out. You would instead reach out the manufacturer for an Engineering Judgement. This would entail providing as much information to the manufacturer as possible regarding the fire penetration, including all the parameters we discussed before. You could even provide pictures of the penetration. Once all of that information has been sent, the manufacturer’s engineering team can come up with a custom design for a firestop assembly that would be tailored to your specific fire penetration. This usually consists of a combination of the manufacturer’s firestop assemblies to meet your specific requirements. Once received, this engineering judgement is to be followed like an instruction pamphlet to properly obtain the required rating.
Putting what you have learned into practice
Now that we’ve discussed all the different ways of prescribing firestop assemblies, it’s up to you as the contractor or technician to put this into practice. As part of the informed group, it’s our duty to share this information with those that are not informed. As mentioned earlier, even though firestopping may seem like a small piece of the equation, any line of defense is only as strong as it’s weakest link. With the prevalence of improper or missing firestopping, it is paramount that the importance of firestopping be stressed. Many fire alarm specifications cover the entire topic under one all-encompassing sentence. “Contractor is responsible for providing firestopping as required”. As part of the contract, it is key to understand the nuances of prescribing the proper firestop assembly for the respective penetration. As the subject matter experts, we need to do our part to ensure the integrity of the building fire protection systems remain continuous throughout. Where the building owners might not know, we have to do our part to educate. If our employees are unaware, it’s our job to teach them the proper way. A little bit of proactivity goes a long way in keeping our buildings safe and compliant.
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