FINAL AIR CLEARANCE

Reg 8 • Colorado Asbestos Getting Calibrated with Final Air Clearances How we verify air quality and what methods are used to do it

​What is a Final Air Clearance After Asbestos Abatement?

When an asbestos abatement or major spill cleanup is finished, the work area might look clean – plastic down, debris removed, HEPA vacuuming done. But you can’t see asbestos fibers with the naked eye.
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That’s where final air clearance comes in. It’s the last, critical quality-control step that confirms airborne fiber levels are low enough for people to safely re-occupy the space and for the contractor to demobilize.
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What is a Final Air Clearance?

Final air clearance (also called clearance air monitoring or post-abatement air testing) is a set of air samples collected after:

1. All asbestos removal/disturbance is complete.
2. The area has been thoroughly cleaned (wet wipe + HEPA vacuum).
3. A certified inspector/air monitoring specialist (AMS) has passed the final visual inspection (no visible dust or debris).

Only after the visual passes do we run air pumps to collect samples on filters. Those filters go to a lab for analysis by PCM or TEM, and the results are compared to regulatory clearance criteria.
Typical regulatory thresholds:

• PCM clearance: ≤ 0.01 fibers per cubic centimeter (f/cc) for each of at least five samples in the work area. 
• TEM clearance: average of five samples inside the work area ≤ 70 structures per square millimeter (70 s/mm²), with sufficient air volume per sample. 

If the area passes, containment can be broken down and people can re-enter. If it fails, the work area must be re-cleaned and re-tested.

Colorado’s Regulation 8, Part B requires final visual inspection plus air clearance on most permitted abatement projects. In non-school buildings, the AMS can use the PCM sampling method and TEM in some cases, especially for schools and specific project types.

How Final Air Clearance Works (Step-by-Step)Here’s the basic flow for a typical regulated project:

1. Final visual inspection
   • Conducted by a certified Air Monitoring Specialist (AMS) or similar role.
   • The work area must be free of visible dust and debris on all surfaces. 
2. Aggressive air sampling setup
   • Critical barriers stay in place.
   • Fans and a leaf blower are used to agitate the air and dislodge fibers from surfaces.
   • This simulates occupied conditions and ensures the sampling captures any remaining fibers.
3. Air sample collection
   • A minimum number of samples (commonly 5+ inside the work area) are collected using calibrated pumps.
   • Pumps run long enough to pull sufficient volume (e.g., ≥1,199 liters on a 25 mm filter for TEM under AHERA). 
4. Laboratory analysis (PCM or TEM)
   • Filters are analyzed by a NVLAP/AIHA-accredited laboratory using standardized methods (e.g., NIOSH 7400 for PCM; EPA AHERA method for TEM). 
5. Compare results to clearance criteria
   • If all PCM samples are ≤0.01 f/cc or
   • If TEM averages are ≤70 s/mm², the area passes final clearance. Otherwise, re-cleaning and re-testing are required.

PCM vs TEM: Which Clearance Method is Right for Your Project?

The “right” method depends on a mix of regulatory requirements, project conditions, and risk tolerance:

1. Regulations & building type
   • K-12 schools: AHERA and Colorado Regulation 8 often require TEM for projects over certain trigger levels. 
   • Most commercial/residential projects: PCM is commonly used, unless the project design, permit conditions, or local authority specify TEM.
2. Dusty or complex environments
   • If you expect lots of non-asbestos fibers (e.g., post-fire, heavy renovation dust, or outdoor soil work), TEM is usually a better choice because PCM can over-count non-asbestos fibers. 
3. Budget and schedule
   • PCM is more affordable and faster, which can be important on tight schedules.
   • TEM adds cost and time, but rules out uncertainty and may prevent arguments about whether clearance truly demonstrated an asbestos-free environment.
4. Risk tolerance & stakeholder expectations
   • For hospitals, schools, long-term care facilities, or high-profile projects, owners often prefer TEM for added assurance and defensibility.
   • For straightforward projects in simpler environments, PCM may be fully adequate and compliant.

PCM sampling is less expensive, but is it right for your project? An experienced AMS must considering the broader implications, chances of failure or circumstances that may make it less appropriate for situation, while being mindful of the immediate cost and defensibility of their results and, in some cases, both methods might be the best option to verify any lingering asbestos hazards.

If you're dealing with asbestos abatement and have questions about a final air clearance or are uncertain about which method is the best option for your situation, contact Advent Asbestos Consulting to answer your questions and gain the professional guidance needed to ensure your health is protected with proper sampling techniques backed by quality analytical results.