OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 30 Demolition

Section 417 Hazardous substances

Subsection 417(a)

A structure that is being demolished may have at one time been used to store, manufacture or process a harmful substance. Harmful substances may also be present in the building structure.

A harmful substance is defined as a substance that, because of its properties, application, or presence, creates or could create a danger, including a chemical or biological hazard, to the health and safety of workers exposed to it.

This section of the OHS Code requires that all chemical and biological substances that could pose a hazard to workers during demolition be removed from the structure (or part of the structure being demolished) prior to demolition. This applies to a wide range of substances, including the following:


  • insulation (fiberglass, asbestos, refractory ceramic fibre)
  • building materials containing asbestos (see Chapter 1 of the Alberta Asbestos Abatement Manual for examples)
  • lead paint
  • mercury (fluorescent lights, switches, gauges)
  • polychlorinated biphenyls (liquid cooled electrical equipment, fluorescent light ballasts, paints, electrical insulating materials)
  • paints and solvents
  • oils and lubricants
  • fuels (gasoline, diesel)
  • batteries
  • process chemicals
  • glues
  • air conditioning system or cooling system chemicals (freon, halon, other chlorofluorocarbons)
  • compressed gases
  • welding rods and solder


  • mould
  • bacteria (medical waste, human or animal waste)
  • animal or human waste (sewage contamination, manure, bird droppings, rodent droppings)

The above list provides some examples of harmful substances that may be encountered, but is not a comprehensive list. The employer must, as part of the hazard assessment required by Part 2 of the OHS Code, identify harmful substances that may be present at the work site. The assistance of a consultant who can conduct a survey of the building for hazardous materials may be needed.

For all demolition projects, a written hazard assessment is required prior to work beginning. If substances are identified that may pose a hazard to workers during the demolition, these substances must be removed before work begins. The employer must consider both direct hazards e.g. contact with lead paint, and indirect hazards e.g. exposure to dust containing lead paint. Alternatively, the employer must develop work procedures that reduce or remove the potential hazard e.g. dust control measures, use of enclosures around demolition areas, etc.

Part 4 of the OHS Code requires that all asbestos-containing materials be removed prior to demolition. Asbestos-containing materials are considered to be materials that contain 1 percent or more asbestos by weight i.e. in the individual material, not aggregate waste. However, regardless of the asbestos content, if asbestos fibres may be released in amounts that reach or exceed the occupational exposure limit for asbestos, then the work site is considered a “restricted area”, as defined in section 1 of the OHS Code. For more information regarding asbestos removal prior to demolition, see Chapter 5 of the Alberta Asbestos Abatement Manual.

Alberta Asbestos Abatement Manual

Although not addressed in the OHS Code, the employer needs to determine the appropriate method for disposing of the demolition waste. Requirements for waste disposal are covered under environmental legislation which is administered by Alberta Environment and Sustainable Resource Development. The employer needs to contact the appropriate environmental authorities and the landfill to determine disposal requirements. In addition, the employer must ensure that the waste materials are contained in a manner so that they will not pose a hazard to workers transporting the waste or to workers at the disposal facility.

Subsection 417(b)

Any concrete that is to be included in the demolition must be assessed to determine if there are any facilities embedded in the concrete. As an example, there may be conduits carrying electrical lines, water/sewage lines, product lines, etc. It is important that workers know of the presence of such lines, their locations and whether or not they are carrying anything that might be harmful or injurious to workers. Concrete-embedded facilities must be identified, located and marked in accordance with section 447.