What is the acceptable fiber level for air clearance to release a contained area?

The correct value for the acceptable fiber level for air clearance to release a contained area is indeed less than 0.01 fibers per cubic centimeter (f/cc). This level represents a significant safety margin for ensuring that the air quality meets health standards before the area is reoccupied. The threshold is often set at 10% of the Occupational Exposure Limit (OEL) for asbestos and similar contaminants to ensure that no adverse health effects occur due to residual fibers in the air following abatement or containment activities.

Setting the acceptable level for air clearance at this threshold provides a buffer that takes into account variability in measurement and possible short-term exposure during the clearance process. It assures that even if workers inadvertently breathe in some fibers, the risk of respiratory issues or other health effects remains very low.

In contexts where air quality standards are being established, particularly in settings involving hazardous materials like asbestos, following such stringent guidelines is crucial for the safety and health of individuals who may enter the area following clearance.