Annulus (firestop)
Encyclopedia
Penetrant
Penetrants, or penetrating items, are the mechanical, electrical or structural items that pass through an opening in a wall or floor, such as pipes, electrical conduits, ducting, cables and cable trays, or structural steel beams and columns...
and whatever surrounds it, such as the sides of an opening or a sleeve
Sleeve (construction)
In construction, a sleeve is used both by the electrical and mechanical trades to create a penetration.-Materials:Sleeves can be made of:* sections of steel pipe* plastic* sheet metal* proprietary devices that are listed firestop components...
, as the case may be.
Sometimes an annulus can be "offset", meaning that the penetrant is not centred. If the firestop was tested
Fire test
A fire test is a means of determining whether or not fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation. Successful tests in laboratories holding national accreditation for testing and certification result in the issuance of a...
only to a perfectly centred opening, an offset may disqualify it for use in the field.
In practical terms, an offset penetrant or annulus may very well present an added degree of difficulty for passing the fire test
Fire test
A fire test is a means of determining whether or not fire protection products meet minimum performance criteria as set out in a building code or other applicable legislation. Successful tests in laboratories holding national accreditation for testing and certification result in the issuance of a...
. A metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
lic sleeve as well as a metallic penetrant will conduct heat through the firestop. Insulation on the bottom of floor systems or in the middle of wall systems, as is the case with caulking or paint based (soft) systems, will encourage more heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
to travel through the sleeve and the penetrant, which can put more stress on the seal on the unexposed side. In the case of a thin (below 4") firestop mortar
Mortar (firestop)
Firestop mortars are mortars most typically used to firestop large openings in walls and floors required to have a fire-resistance rating. They are passive fire protection items...
, there is also more potential hazard from tight annular spacing because metal expands during the fire, thus squeezing the firestop - only to rapidly shrink when hit with the hose-stream test, which can let water through, thus failing the H rating
Fire-resistance rating
A fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test. This can be quantified simply as a measure of time, or it may entail a host of other criteria, involving other evidence of functionality or fitness for...
in Canada or the entire rating in the US, where hose-stream testing is mandatory. Such a failure may no longer be visible once the test assembly has reached ambient temperatures again.
For all these considerations, the annular space is a critical aspect of field approvals.