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According to the test standard EN1366-3 for penetration seals (cable and pipe penetrations) a mixed penetration seal is defined as a penetration seal intended for penetrations where more than one type of service passes through. Types of services are cables and pipes, or pipes made of different material groups like copper, steel, composite pipes or plastic pipes.

In current practice, installations of building equipment and appliances like cable and pipe runs are frequently planned in bundles. Due to the fact that space in hallways, shafts or above suspended ceilings is restricted and limited, these cable or pipe runs are basically designed side by side ignoring a minimum distance between each other. However, as soon as these installations pass through fire-rated walls or floors, they pose a risk and end up in situations that are not covered in a firestop approval or assessment. The problem is that minimum distances have to be followed to secure stability and resistance of a penetration seal in case of a fire.

Mixed penetration seals need to be specifically tested by manufacturers. Not all available firestop solutions can be offered for mixed openings. It is specifically mentioned in the technical description of the respective ETA (European Technical assessment) of a firestop product which additional components can be used as a part of a mixed penetration seal. The ETA clearly defines how many penetrants of which type and material, which diameters and which opening sizes are tested and approved for a given fire resistance rating.

In other words, technical assessments do exist for certain firestop products with clear field of application descriptions. But as we frequently encounter larger opening sizes through which different penetrants are pulled through by different trades, actually installing firestop solutions remains very challenging.

The key challenges of mixed penetrations

The following are just some of the key challenges of mixed penetrations:

• In all ETAs, clear restrictions on minimum distances are defined. This is very challenging as, as said above, most planning is done with clear space limitations on cable and pipe runs. When all these media are going through the opening, minimum distance requirements for the fire penetration seal can often not be met. This results in expensive re-cabling or rework on pipe runs, additional casings or even a complete change of plans for electrical or mechanical installations.

• In some cases, different contractors use different materials or materials from different manufacturers in different phases of the installations to close and seal the openings. However, using different materials or systems will lead to a loss of approval and is seen as a major deficiency in respect to compliance and building approval.

• Mixed penetrations require in most cases many different products to be installed. For plastic pipes, additional firestop collars have to be fixed, different sealants or fillers need to be used to seal off or close gaps or joints and additional measures need to be taken to achieve high fire resistance ratings like EI120 (for example additional insulations around cable trays or pipes). This requires high levels of competence and knowledge from contractors.

• Many systems for mixed penetrations are so-called firestop mortars or coated board systems. The installation of such systems is not easy and time consuming, dirty and requires contractors to be competent and have extensive approval knowledge.

• Who is actually assigned and commissioned to do the final firestopping of the opening? In many countries, firestop specialist contractors are selected to do this cumbersome job. Here it is important to select most experienced and professional companies who also have strong partnerships with established manufacturers.

• It is also common practice to include ducts and dampers in a large mixed penetration seal. Here, as the test standard for dampers is different and is a separate application, there is basically no approval for a mixed penetration seal in combination with cables or pipes. Damper manufacturers have to be contacted separately.

How do I find the right Firestop solution for mixed openings?

The common challenges listed above confirm that mixed penetrations do have disadvantages. Installation is complex, maintenance during the operational phase of a building is even more complex and the risk of installing a mixed penetration seal wrongly outside of the approved application range is always present.

For electrical or mechanical planners and specifiers it is always recommended to design separate trade specific openings at an early stage of the planning process. This avoids complexity, communication as well as coordination problems. Most of these openings can be smaller and offer the chance to select or specify better suited trade-specific firestop solutions which can be installed faster, have more dedicated advantages and therefore offer better control during installation, documentation and the inspection processes.

That said, many planners and designers do foresee large openings in fire-rated walls or floors.

Table 1. selection criteria for mixed penetration

Table 1 above shows some key parameters to be looked at when planning, selecting and specifying product solutions for mixed penetration seals.