Work with asbestos is divided into four classes based on the nature of the asbestos material and the type of activity being performed:
- Class I asbestos work involves the removal of thermal system insulation (TSI) and surfacing asbestos-containing materials (ACM) including presumed asbestos-containing materials (PACM). This is the most hazardous class of asbestos work.
- Class II asbestos work includes activities involving the removal of ACM that is not TSI or surfacing material, such as asbestos-containing wallboard, floor tiles, roofing materials, and siding.
- Class III asbestos work covers repair and maintenance operations where ACM or PACM is likely to be disturbed.
- Class IV asbestos work involves maintenance and custodial activities where employees come into contact with but do not disturb ACM or PACM, and includes cleaning up asbestos dust, waste, and debris generated by Classes I, II, and III work.
These classifications are used to determine the specific safety, control, and regulatory requirements that apply depending on the risk level of the asbestos-related activity.