Fire Stopping Explained: Products, Tests and Ratings

Nobody checks a hole. They check the wall. The hole comes later, cut by an electrician who was told to get the cables through by Thursday. Fire stopping is the job of closing those holes again. Do it right and the wall still stops fire. Do it wrong and it is just a wall with a gap in it.

We supply fire stopping products to contractors, distributors and buyers in Africa, Europe and the United States. We do not install them. That keeps our job simple: make sure what you buy matches what the building needs, and that the test paperwork actually proves it. This page explains what the products are, how they are tested, and the one mistake that ruins more seals than bad workmanship ever does. It sits under our wider guide to passive fire protection.

What fire stopping is

A fire wall is a promise about time. It says fire on one side will stay on that side for 60 minutes, or 120, or whatever the drawing asks for. That promise only holds if every way through the wall is closed to the same standard. Pipes and cables do not care where the fire walls are. A normal building ends up with hundreds of these crossings: waste pipes, cable trays, air conditioning lines, sprinkler pipes, door access wiring. Every one of them is a hole cut into something that was designed solid. The word firestop is used interchangeably in North American practice and in a lot of product literature, and it means the same thing. The two terms describe the same job, and buyers see both on drawings and datasheets depending on who wrote them.

Why the hole is the weakest part of the wall

Consider what a plastic waste pipe does in a fire. It softens, then it disappears, and the neat 110 mm opening it occupied becomes a clear chimney between two floors. A sealant cannot solve that. Something has to expand fast enough to fill the void the pipe used to be. Now consider a steel pipe in the same opening. It does not disappear. It conducts heat straight through the wall and can ignite material touching it on the cold side several minutes before flame arrives. Two openings that look identical on a drawing need completely different answers. This is why a schedule that lists only the number of penetrations and a product code is not a specification, and why we ask what is going through the hole before we ask how many units are needed.

Fire stopping products and where each one belongs

Choosing between them is less about the product and more about the opening. Narrow gaps around metal services take a sealant, usually with a backing material at a stated depth, because depth is part of the tested arrangement rather than a matter of taste. Plastic services take a collar or a wrap containing intumescent material, sized to the pipe diameter. Large or crowded apertures with cable trays take a mortar, a board and batt build-up, or pillows where cabling will be added later. Pre-formed devices exist for common repeated details and remove some of the site variation. Our SIMFY FIRESYS category pages group these by failure mode rather than by brand, because that is how a specifier thinks about them.

Penetration seals and linear gap seals are different problems

The two have separate test standards for good reason. BS EN 1366-3:2009 specifies the test methods and evaluation criteria for penetration seals where services pass through separating building elements, and it assesses the effect of the penetration on the integrity and insulation of the element as well as the performance of the seal itself. BS EN 1366-4 gives a method for determining the fire resistance of linear joint seals based on their intended end use, and it covers two distinct scenarios: joints with no mechanically induced movement, and joints where movement is induced before or during fire exposure. That second scenario is the one people forget. A slab edge moves. A wall head deflects under load. A seal that passed static testing may have no evidence at all for a joint that is expected to open and close, and the movement class is part of the classification, not a footnote to it.

The tests behind the ratings

BS EN 1363-1:2020 establishes the general principles for determining fire resistance under standard fire exposure, including the temperature and time curve that the individual methods sit on. The classification then comes from BS EN 13501-2:2016, which provides the procedure for classifying construction products and building elements using data from fire resistance tests. That is the source of E for integrity, meaning flame and hot gas do not pass, and I for insulation, meaning the unexposed face stays below defined temperature limits. EI 120 means both, for 120 minutes. The specimen is built into a supporting construction, heated on one side to the defined curve, and watched for flame, for gaps that open, and for temperature rise on the cold face. Whichever criterion fails first sets the number. That is why a seal can carry a high integrity figure and a much lower insulation figure, and why quoting only the larger of the two is a habit worth distrusting.

North American practice reports the same physics differently. UL 1479, Fire Tests of Penetration Firestops, evaluates through-penetration and membrane firestops in fire-resistive wall, floor and floor-ceiling assemblies, and assigns an F rating for the time before flame appears on the unexposed surface, a T rating that adds a temperature rise criterion, an L rating for air leakage in cubic feet per minute per square foot, and a W rating for resistance to water passage. ASTM E814 assigns F and T ratings on the same logic. An F rating is not a translation of an EI classification, and treating them as equivalent is a decision an approving authority has to make, not a buyer.

The thing that voids more seals than bad workmanship

Read the title of ASTM E814 and it is already telling you this. The standard is called Standard Test Method for Fire Tests of Penetration Firestop Systems. Not products. Systems. UL 1479 describes what it evaluates in the same way, as firestops used in openings within specified assemblies. BS EN 1366-3 assesses the seal together with the element it sits in and the service that passes through it, covering the effect of the penetration on the element as well as the performance of the seal. Every one of these documents is measuring a combination, and the number that comes out the other end belongs to that combination rather than to any single item inside it. A tube of sealant has no rating of its own. It has a role in arrangements that were tested, and a list of the arrangements it has been proved in. Those are different claims, and only the second one can be checked against a wall.

So the practical failures are rarely dramatic. A collar sized for a 110 mm pipe goes onto a 125 mm pipe because that is what turned up. A seal tested in dense blockwork goes into a plasterboard partition. Pipe insulation is stripped back at the wall to make the sealant easier to tool, when the tested detail carried the insulation straight through. Cables are added to a sealed tray six months later and the mortar is patched with something from a different manufacturer. In each case the workmanship may be tidy and the product genuine, and the classification still does not apply, because the arrangement that was tested is not the arrangement that exists.

Two habits fix most of this. Ask for the classification report rather than a brochure rating, and read its field of application, which states the range of substrates, opening sizes and service diameters the result may be applied to. And treat any substitution as a technical change needing its own evidence, not a purchasing decision. That is the sequence behind how we work on every enquiry.

Reading a certificate without being caught out

Regulation (EU) No 305/2011, the Construction Products Regulation, requires manufacturers to draw up a declaration of performance for products covered by a harmonised specification and to apply the relevant marking, and it lists safety in case of fire among the basic requirements for construction works. That declaration is genuine and worth having. It also cannot tell you your opening was ever tested, because the manufacturer did not draw your building. A real classification report names an accredited laboratory, carries a report number and date, states the exact configuration tested, and sets out what the result may be extended to. A rating quoted with no configuration attached is marketing. Third-party certification adds a further layer, because a scheme audits a holder against defined conditions, and the certificate is only as wide as the scope printed on it. Reading that scope carefully answers most of the questions buyers actually have, and it takes a few minutes.

The regulatory mood has hardened in several markets. The Building Safety Act 2022 in the United Kingdom set up a building safety regulator, placed duties on accountable persons for higher-risk buildings, and included provisions on construction products liability reaching manufacturer accountability and cost contribution orders where products proved defective. For a buyer the message is simple enough: the evidence chain is expected to be traceable, and the purchaser sits inside it. Keeping that chain intact is what our approach to trust and quality exists to do.

Older and newer test regimes still appear side by side

Neither regime is wrong on its own. The mistake is assuming an equivalence nobody has demonstrated, then discovering at handover that the approving authority wanted evidence under the other route. Approved Document B, the statutory guidance covering fire safety matters within and around buildings in England, is published in two volumes in a 2019 edition carrying later amendments, and those amendments are part of why older and newer references sit together on the same job. When a requirement arrives naming a BS 476 rating, we say so plainly and ask which evidence the authority will accept, rather than quietly shipping the nearest European equivalent and letting the difference surface later. The same care applies across our export markets, where the accepted route varies by country and sometimes by client.

Where we fit, and where we do not

Our work sits before site. We take a requirement, identify product whose manufacturer holds the test evidence the specification calls for, verify the supplier, and can arrange factory audit and pre-shipment inspection so what ships matches what was quoted. We hold no third-party certification ourselves and claim none. The certificates belong to the manufacturers whose product we supply, which is a different and more honest statement than the one some suppliers make.

We are the wrong choice in three cases: a single item needed tomorrow, which a local distributor will handle better; a detail that needs designing, which is a fire engineer’s work; and any situation where the paperwork needs to be flexible, where the answer will be no. If none of those describe you, send us your requirement with substrate, opening size and service details, and you will get a specific technical answer rather than a catalogue.