In the past, many building materials, especially bricks used to contain insulating material such as asbestos, and its a comon worry that if you are working out of the developed world, that you may still come across it. However, usage of asbestos in building material has been banned world wide. As such, the hollow brick material does not contain asbestos or any other hazardous substance in its composition – it in fact relies on air to act as the insulating agent.