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Electrical cable through-penetration, firestopped by an intumescent sealant, to restore the two-hour fire-resistance rating of the concrete floor. The cables are the penetrants.

This drawing is intended to illustrate common guidelines for the forming of through-penetrations such that proper sizing and costing for firestops can occur. In the case of sleeving, which is limited to fire-separations made of concrete and masonry, the mechanical and electrical trades are responsible for the sizing of the openings because they apply the sleeves. In the case of drywall fire separations, the opening size is determined by the drywall contractor, unless the mechanical and electrical trades are contractually obliged to provide sleeving here as well, with proper fastening methods that must be subject to bounding. All trades shall can use this guideline. This permits accurate priceing as well as accountability for field variances. Exceptions are penetrations in timber floors. Often, timber floor openings are simply cut by means of a chainsaw. In this case, the width of the blade will determine sizes. Sizing of all openings has significant impact upon bounding. Therefore, communication between all affected trades is of great importance before any openings are made.

1000MCM power cables, penetrants in a firestop mortar test assembly.

Steel beam through-penetration. The firestop surrounding the beam is incomplete - packing only, sealant is yet to be applied. The beam itself must be treated with fireproofing to prevent it from twisting and damaging the wall during a fire. The beam is the penetrant.

Sprinkler branch pipe through-penetration with plasticsleeve - missing firestop in concrete fire separation. The branch pipe is a penetrant, as is the plastic sleeve, which is a code violation if left in place, unless subject to bounding with a firestop that permits such sleeving to be left in place.

Cable tray cross barrier firestop test, full scale wall, in Germany as per DIN4102.

A penetrant is the cause for a service penetration firestop. Building codes can refer to mechanical and electrical penetrants as services.

Penetrants are the mechanical, electrical or structural items that pass through an opening in a wall or floor, such as:

• pipe
• Conduit (electrical)
• ducting
• cables
• cable trays
• structural steel beams and columns

When these items are traversing a wall or floor assembly required to have a fire-resistance rating, they create the need for an opening, consisting of the space(s) between penetrant and surrounding structure, which must be firestopped in order to restore the fire-resistance rating of the parent assembly, which would otherwise be lost.

Penetrants are typically accommodated by plumbers and electricians, who prepare for them by installing sleeves in concrete walls and floors, before they are poured. In the case of masonry walls, electricians and plumbers tend to be there first and hang sleeves around their piping, ductwork and conduit, where they know from their drawings that blockwalls will be erected, in order to avoid the time and expense of having to cut openings in existing walls and floors.

In the case of drywall assemblies, if the mechanical and/or electrical trades are there before the drywall has been erected, and the M & E trades are contractually obliged to do the firestopping on site, it is not uncommon for these trades to attempt to absolve themselves of the requirement to firestop their openings in the drywall assemblies by claiming that they were there first, meaning that others should take care of the rest. Since drywall contractors are not ordinarily required to do M & E firestopping, the drywall openings can become an item of dispute or neglect, particularly in North American construction. This common issue is easily remedied by designating a separate firestopping sub-contract, whereby a separate speciality sub-contractor firestops all openings on site, mechanical, electrical and structural, as well as the building joints. Care must be taken, however, to ensure proper sizing of the openings for cost control and bounding purposes.

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