OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 4 Chemical Hazards, Biological Hazards and Harmful Substances

Section 35 Encapulation, enclosure or removal of asbestos

When a structure with asbestos-containing materials is being altered or renovated, the disturbance of the asbestos may result in the uncontrolled release of airborne fibres. To prevent this, the employer must ensure that the asbestos-containing materials are removed, encapsulated or enclosed. When deciding which of the corrective actions is most appropriate, consideration should be given to the condition of the asbestos, its location, function and the cost of the proposed method of controlling exposure.

Removal, encapsulation and enclosure are corrective measures that can be used separately or in combination. Removal completely eliminates the source of exposure and, as a result, offers a permanent solution. Enclosure and encapsulation are containment methods that do not remove the potential source of asbestos exposure. If asbestos-containing materials remain in place, a management plan will be required for the building.


Asbestos-containing materials are removed from the underlying surface and collected and placed in containers for disposal at an approved waste disposal site. This process is the most expensive control method in the short term and may require an interruption of building activities. Removal is a prerequisite for demolition of a structure containing asbestos-containing material.


During encapsulation, asbestos-containing materials are coated with a bonding agent called a sealant. Sealants penetrate and harden the material and/or cover the surface of the material with a protective coating i.e. bridging sealants. Sealants are applied over the surface of the material using airless spray equipment at a low pressure setting. If a penetrating sealant is used, the person applying the product must ensure that it penetrates through the material to the underlying support. Bridging sealants must form a tough skin that can withstand moderate impact, be flexible and flame retardant, resist deterioration over time and be non-toxic. The encapsulant should meet the requirements of Canadian General Standards Board Standard CAN/CGSB‑1‑205‑94, Sealer for Application to Asbestos Fibre Releasing Materials, or an equivalent standard.


Enclosure is the placement of a physical barrier between the asbestos-containing materials and the building environment. Drywall covering is an example of a type of acceptable enclosure. Since the asbestos is not removed, fibres will continue to be released and will accumulate behind the barrier. If the enclosure is damaged or entered for maintenance, these fibres may be released into the building environment.

Management plan

When asbestos-containing materials remain in place in a building, a management plan is needed. The plan should address the following;

(a) amount and type of asbestos-containing materials in the building;
(b) inspection frequency and procedures;
(c) training requirements for maintenance workers and others who may come into contact with the materials or work near them;
(d) procedures to be followed if the materials are damaged or in other emergency situations;
(e) procedures to be followed if the condition of the materials change or work routines are altered;
(f) notification procedures for building occupants; and
(g) labelling of asbestos-containing materials.

Additional information about these methods and asbestos abatement in general can be found in the Alberta Asbestos Abatement Manual.

Alberta Asbestos Abatement Manual