Asbestos Sealant

Asbestos sealants are a category of construction sealants — including caulks, fire-stop compounds, and joint fillers — that were manufactured with asbestos fibres to provide heat resistance, flexibility, and fire-stopping capability. Produced from the 1940s through to the mid-1990s, these products were used extensively in commercial, industrial, and institutional buildings for sealing expansion joints, fire-stopping penetrations through walls and floors, and connecting HVAC ductwork.

The asbestos content in sealant products ranges from 3 to over 20 per cent, depending on the formulation and intended purpose. Chrysotile was the most commonly used fibre, though high-temperature fire-stop sealants sometimes contained amosite or crocidolite for enhanced thermal performance. The fibres gave the sealant improved cohesion, crack resistance, and the ability to maintain a seal under thermal cycling.

Asbestos sealants are found in a wide variety of locations within buildings. Fire-stop sealants are typically found packed around pipes, cables, and ducts where they pass through fire-rated walls and floors. Expansion joint sealants are found in concrete floors, between cladding panels, and around structural elements. HVAC duct sealants are found at joints and connections in heating, ventilation, and air-conditioning systems.

The risk from asbestos sealant depends on its condition and the type of disturbance. Soft, intact sealant may present a low risk, but dried, cracked, or crumbling sealant can readily release asbestos fibres. Removing or disturbing sealant during maintenance, renovation, or demolition work can generate significant fibre release, particularly when the material is scraped, cut, or drilled.

Building managers and maintenance personnel should be aware that sealants in older buildings may contain asbestos. Before any work that would disturb sealant materials in buildings constructed before 1995, samples should be collected and tested. If asbestos is confirmed, a licensed contractor must carry out the removal using wet methods, appropriate containment, and personal protective equipment.