Intumescent Seals is a division of Dixon International Group Limited


PVC pipes are commonly used in buildings for the transportation of waste water or rainwater. Where such pipes penetrate fire compartment walls or floors they must be adequately protected to maintain the fire resistance of the building’s fire compartments in the event of a fire. THERM-A-CLOSE is a simple and cost effective way of achieving and maintaining this fire resistance integrity.


THERM-A-CLOSE is a steel collar lined with THERM-A-FLEX intumescent material. The steel collar is formed in two halves which fit together during installation and includes integral fixing lugs. The collar is powder coated to provide effective corrosion protection. At approximately 180°C the THERM-A-FLEX begins to expand and, restrained by the steel shell, generates sufficient pressure to crush the PVC pipe within in the collar thereby providing fire resistance protection.


THERM-A-CLOSE intumescent collars are suitable for sealing PVC pipe penetrations through a range of different construction materials.

Cast concrete floors: THERM-A-CLOSE is fixed to the underside of the floor or cast within the floor slab in line with the underside of the slab.

Concrete/block walls: THERM-A-CLOSE is face fixed to either side of the wall.

Drywall / stud walls: THERM-A-CLOSE is face fixed to either side of the wall.

Mineral wool fire bat penetration seals: THERM-A-CLOSE is fitted through the full thickness of the fire bat around the PVC pipe.

THERM-A-CLOSE is fixed to the supporting construction around the pipe penetration with non combustible fixings.


The achievable fire resistance (FR) performance of THERM-A-CLOSE is dependent on the supporting construction:

FR Integrity
FR Insulation
Drywall/stud wall 120min 120min
Concrete/block wall 240min 240min
Concrete floor (Surface) 240min 240min
Concrete floor (cast in)* 180min 180min
*(Up to 110mm dia)    



THERM-A-CLOSE is available in the following sizes:

OD/mm ID/mm OD/mm Height
32-55 55 72 50
56-82 82 103 50
83-110 110 135 50
111-125 125 160 60
126-160 160 203 60
200 200 269 78
250 250 328 78
315 315 390 78


Test Evidence

THERM-A-CLOSE meets the performance requirements noted above in accordance with BSEN1363-1:1999, BSEN1363-3:2004 & BS476-20:1987

Copies of test reports and other performance evidence are available on request.

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