Asbestos Air Monitoring During Abatement and Demolition
OSHA PEL, excursion limit, PCM air monitoring types, work classifications, hot demolition rules, and clearance sampling requirements.
OSHA Exposure Limits
OSHA sets two exposure limits for airborne asbestos fibers under both the construction standard (29 CFR 1926.1101) and the general industry standard (29 CFR 1910.1001):
Permissible Exposure Limit (PEL): 0.1 fibers per cubic centimeter (f/cc) as an 8-hour time-weighted average (TWA)
Excursion Limit (EL): 1.0 f/cc as a 30-minute short-term exposure limit
Employee exposure is determined from breathing zone air samples and analyzed by Phase Contrast Microscopy (PCM). Exposure is assessed without regard to respiratory protection - meaning even if a worker is wearing a respirator, the airborne concentration determines compliance with the PEL.
Work Classifications
OSHA’s construction standard classifies asbestos work into four classes based on the type and risk level of the activity. The classification determines which monitoring, controls, and worker protections are required.
Class I
The most hazardous category. Includes activities involving the removal of TSI and surfacing ACM/PACM. Examples: removing pipe insulation, stripping sprayed-on fireproofing.
Requirements: Negative pressure enclosure, HEPA-filtered local exhaust ventilation, wet methods, mandatory personal air monitoring unless a negative exposure assessment (NEA) has been established.
Class II
Activities involving the removal of ACM that is not TSI or surfacing material. Examples: removing floor tile, ceiling tile, roofing, transite siding, gaskets.
Requirements: Wet methods, critical barriers where appropriate, personal air monitoring required unless an NEA has been established.
Class III
Repair and maintenance operations where ACM or PACM is likely to be disturbed. Examples: drilling into ACM walls, replacing a section of pipe insulation, cutting into a ceiling that contains ACM.
Requirements: Wet methods, local exhaust ventilation where feasible, initial exposure assessment required.
Class IV
Maintenance and custodial activities during which employees contact ACM or PACM but do not disturb it, and cleanup of ACM/PACM dust, debris, and waste. Examples: sweeping up debris containing ACM, cleaning up after abatement work.
Requirements: Wet methods, HEPA vacuuming, initial exposure assessment required.
Types of Air Monitoring
Personal Monitoring
Air is sampled from the worker’s breathing zone using a calibrated personal sampling pump and a 25mm mixed-cellulose ester (MCE) filter cassette. The cassette is attached near the worker’s collar or lapel, and the pump is clipped to the belt. Sampling is conducted during the work period to capture a representative 8-hour TWA.
Personal monitoring is used for OSHA PEL compliance and must be performed for all Class I and Class II work unless a negative exposure assessment has been documented.
OSHA requires that monitoring results be reported to affected employees within 15 working days of receiving the results.
Area Monitoring
Air is sampled at a fixed location using a pump and cassette on a tripod or mounted surface. Area monitoring serves several purposes:
Background monitoring - Conducted before an abatement project begins to establish baseline fiber levels in the ambient environment. Important for establishing that any fibers detected during or after abatement originated from the project, not from pre-existing conditions.
Perimeter monitoring - Conducted at the boundary of the regulated area or containment during abatement to verify that fibers are not escaping the work area. Samples are placed outside the containment barrier, near doorways, in adjacent occupied spaces, or at building air intakes.
Clearance monitoring - Conducted after abatement is complete and the work area has been cleaned, to verify that airborne fiber levels have returned to acceptable levels before the area is reoccupied.
Clearance Sampling
Clearance sampling is the final step before a contained abatement area is released for reoccupation. Requirements vary by regulatory program:
AHERA (schools): Requires aggressive air sampling with TEM analysis. Before sampling, the area is agitated using leaf blowers, fans, or similar equipment to simulate normal activity and resuspend any settled fibers. The clearance criterion is 0.01 f/cc by TEM. This is the most stringent clearance standard.
OSHA (non-school Class I work): Requires visual inspection (no visible debris or dust) and may require air monitoring. The standard does not prescribe a specific clearance level for non-school work, but many project specifications reference 0.01 f/cc by PCM or TEM as a clearance criterion.
State and local requirements: Some jurisdictions have additional clearance requirements. Check the applicable project specifications and any state-specific rules.
Negative Exposure Assessment
OSHA allows employers to forgo ongoing personal monitoring for Class I and Class II work if they can demonstrate a negative exposure assessment (NEA). An NEA requires:
- Prior monitoring data from asbestos jobs within the last 12 months
- Monitoring conducted under workplace conditions closely resembling the current job (same processes, material types, controls, work practices, and environmental conditions)
- Data showing a high degree of certainty that exposures will not exceed the PEL or excursion limit
Or, initial monitoring of the current job showing exposures below the PEL and excursion limit.
If an NEA is established, monitoring may be discontinued unless conditions change.
Hot Demolition
A hot demolition - demolishing a structure without first removing ACM - is one of the most serious violations under NESHAP. The regulation requires that all RACM be removed before any demolition activity that would break up, dislodge, or disturb the material.
When Hot Demolition Is Permitted
Only in genuine emergencies:
- The facility is structurally unsound and in danger of imminent collapse
- An emergency makes abatement before demolition impractical or unsafe
- Other conditions that create an immediate danger to life or property
Requirements During Emergency Demolition
Even during a legitimate emergency demolition:
- The portion of the facility containing RACM must be adequately wetted during wrecking
- Materials must remain wet until collected for disposal
- Emergency notification must be provided to the regulatory agency as early as possible
- All other NESHAP waste handling and disposal requirements still apply
Consequences of Unauthorized Hot Demolition
Hot demolitions conducted without a legitimate emergency justification can result in:
- Significant civil and criminal penalties under the Clean Air Act
- Stop-work orders
- Required cleanup of the demolition site to asbestos standards
- Personal liability for responsible parties
OSHA Recordkeeping
Employers must maintain the following records for asbestos work:
| Record Type | Retention Period |
|---|---|
| Exposure monitoring records | 30 years |
| Medical surveillance records | Duration of employment + 30 years |
| Training records | 1 year beyond last date of employment |
| Objective data (for NEA) | 30 years |
Exposure monitoring results must be reported to affected employees within 15 working days of receipt.
Resources
- 29 CFR 1926.1101 - OSHA Asbestos in Construction Standard
- 29 CFR 1910.1001 - OSHA Asbestos in General Industry Standard
- OSHA ID-160 - Asbestos in Air sampling method
- OSHA Asbestos - Evaluating and Controlling Exposure
- Asbestos Analytical Methods - PCM, TEM, and PLM explained
- Ohio Asbestos Regulations Overview
Frequently Asked Questions
What is the OSHA PEL for asbestos?
The OSHA Permissible Exposure Limit (PEL) for asbestos is 0.1 fibers per cubic centimeter (f/cc) of air as an 8-hour time-weighted average (TWA). There is also an excursion limit (EL) of 1.0 f/cc as a 30-minute short-term exposure limit. These limits apply to all asbestos work under both the construction standard (29 CFR 1926.1101) and the general industry standard (29 CFR 1910.1001).
Who can perform air monitoring for asbestos?
In Ohio, air monitoring during asbestos abatement must be performed by a certified Asbestos Hazard Abatement Air Monitoring Technician, a certified Asbestos Hazard Evaluation Specialist (AHES), or a Certified Industrial Hygienist (CIH). The air monitor must be independent of the abatement contractor - the same company performing the removal cannot monitor its own work.
What is the difference between personal and area monitoring?
Personal monitoring samples air from a worker's breathing zone using a pump clipped to the worker's belt and a cassette attached near the collar. It represents what the worker is actually breathing and is used for OSHA PEL compliance. Area monitoring samples air at a fixed location and is used for perimeter monitoring, background monitoring, and clearance sampling. Both use the same analytical method (PCM) but serve different purposes.
What is a hot demolition?
A hot demolition is the demolition of a structure without first removing all asbestos-containing materials. Under NESHAP, hot demolitions are generally prohibited except in genuine emergencies (structural instability, imminent danger). When an emergency hot demolition occurs, all RACM exposed during wrecking must be adequately wetted and emergency notification procedures apply. Hot demolitions that are not genuine emergencies can result in significant enforcement actions.