Asbestos is a risk to health only when the fibres are dispersed in the air and inhaled into the lungs. When asbestos is contained within another material and fibres are not liberated, the risk to health is minimal., However, any work or process that disturbs the fabric of the asbestos-containing material (ACM) and that releases fibres, such as drilling, cutting, high pressure cleaning, demolishing or even natural deterioration and weathering of the ACM, introduces a serious threat to human health. Materials that are made from pure asbestos or that contain high percentages of asbestos, such as insulation and lagging material, are far more dangerous than low percentage ACMs, such as asbestos-cement products.