Critical Barriers

In addition to all indoor Class II jobs without a negative exposure assessment, employers must use critical barriers over all openings to the regulated area or another barrier or isolation method to prevent airborne asbestos from migrating for the following:

• When changing conditions indicate exposure above the permissible exposure limit, or
• When asbestos containing material is not removed substantially intact.

If using other barriers or isolation methods instead of critical barriers, employers must perform perimeter area monitoring to verify that the barrier works properly. In addition, impermeable drop cloths must cover all surfaces beneath removal activities.

All Class II asbestos work can use the same work practices and requirements as Class I asbestos jobs. Alternatively, Class II work can be performed using work practices set out in the standard for specific jobs.

To learn more about Construction Asbestos Safety visit our Construction Asbestos Safety Online Training web page.