ACM Definitions by Regulation

Regulation	ACM Definition	Key Implication
AHERA (40 CFR 763)	Material containing >1% asbestos	Standard for building surveys and school management
NESHAP (40 CFR 61 Subpart M / OAC 3745-20)	Material containing >1% asbestos	Triggers notification and work practice requirements
OSHA (29 CFR 1926.1101)	Material containing >1% asbestos	BUT OSHA regulates activities involving materials with ANY amount of asbestos

NESHAP Threshold Quantities

These thresholds determine when NESHAP notification and work practice requirements apply to renovation projects. All demolitions require notification regardless of ACM quantities.

Measurement	NESHAP Threshold (RACM)
Linear feet on pipes	260 LF
Square feet on other components	160 SF
Cubic feet (where LF/SF cannot be measured)	35 CF

Ohio Contractor Notification Threshold (OAC 3745-22)

Separate from NESHAP notification, Ohio requires notification when a licensed contractor performs abatement exceeding:

Measurement	Ohio Threshold
Linear feet of RACM	50 LF
Square feet of RACM	50 SF

Projects may trigger notification under both OAC 3745-20 (NESHAP) and OAC 3745-22 (contractor rules). Ohio uses a single combined notification form but the fee structures are separate.

Clearance Levels

Standard	Clearance Level	Method	Applies To
AHERA (schools)	0.01 f/cc	TEM (aggressive air sampling)	K-12 school abatement projects
Common project specification	0.01 f/cc	PCM or TEM	Non-school abatement (not regulatory, but widely used)

OSHA does not prescribe a specific clearance concentration for non-school projects, but most project specifications reference 0.01 f/cc.

AHERA Sampling Minimums

Material Type	Minimum Samples per Homogeneous Area
Surfacing (<1,000 SF)	3
Surfacing (1,000-5,000 SF)	5
Surfacing (>5,000 SF)	7
TSI (homogeneous area)	3
TSI (patch <6 LF or SF)	1
TSI (cement/plaster on fittings per system)	2
Miscellaneous material	2

For miscellaneous and non-friable materials, 2 is the regulatory minimum based on EPA’s interpretation of the plural “samples” in 40 CFR 763.86(c) and (d). The accredited inspector may determine that more samples are necessary. Many inspectors default to 3 per homogeneous area as a conservative practice. Joint compound and add-on materials require 3 samples per homogeneous area per EPA Sampling Bulletin 093094.

OSHA Asbestos Exposure Limits

These limits apply under both the construction standard (29 CFR 1926.1101) and the general industry standard (29 CFR 1910.1001).

Exposure Limit	Concentration	Averaging Period
Permissible Exposure Limit (PEL)	0.1 f/cc	8-hour TWA
Excursion Limit (EL)	1.0 f/cc	30-minute

Exposure is measured by Phase Contrast Microscopy (PCM) from personal breathing zone samples. Exposure determinations are made without regard to respiratory protection.

OSHA Definition of ACM

Under OSHA, asbestos-containing material (ACM) means any material containing more than 1% asbestos. However, OSHA’s construction standard (29 CFR 1926.1101) regulates all work activities involving materials containing any amount of asbestos, not just materials exceeding 1%. See AHERA Sampling and the 1% Threshold for a detailed discussion of this distinction.

Presumed Asbestos-Containing Material (PACM)

In buildings constructed before 1981, the following materials are presumed to contain asbestos under OSHA:

Thermal System Insulation (TSI) - pipe wrap, duct insulation, boiler insulation
Sprayed-on and troweled-on surfacing material - fireproofing, acoustical plaster

PACM can be rebutted by an inspection in accordance with AHERA (40 CFR 763.86) or by bulk sampling by an accredited inspector or Certified Industrial Hygienist (CIH). PACM does not apply to floor tile, wallboard, roofing, or other miscellaneous materials.

Note: The PACM designation is specific to OSHA. AHERA and NESHAP take a broader approach, requiring evaluation of all suspect materials regardless of type. See the discussion of PACM vs. assumed ACBM in our AHERA sampling guide for the full picture.

Work Classifications (Construction Standard)

The construction standard (29 CFR 1926.1101) classifies asbestos work into four categories. Classification determines the required controls, monitoring, and worker protections.

Class	Description	Examples
I	Removal of TSI and surfacing ACM/PACM	Stripping pipe insulation, removing sprayed fireproofing
II	Removal of ACM that is not TSI or surfacing material	Removing floor tile, ceiling tile, roofing, transite siding, gaskets
III	Repair and maintenance likely to disturb ACM/PACM	Drilling into ACM walls, replacing pipe insulation sections, cutting ACM ceiling
IV	Maintenance/custodial contact with ACM/PACM without disturbance; cleanup of ACM debris	Sweeping ACM debris, cleaning after abatement

Required Controls by Class

Requirement	Class I	Class II	Class III	Class IV
Regulated area	Required	Required	Required	Required where airborne levels may exceed PEL
Negative pressure enclosure	Required	Where feasible	No	No
Wet methods	Required	Required	Required	Required
HEPA local exhaust ventilation	Required	Where feasible	Where feasible	No
Personal air monitoring	Required (unless NEA)	Required (unless NEA)	Initial assessment	Initial assessment
Respiratory protection	Required (minimum half-face APR)	Required	Required if above PEL	Required if above PEL
Protective clothing	Required	Required	Required if above PEL	Required if above PEL
Decontamination area	Required (full decon unit)	Required	Required if above PEL	No
Medical surveillance	Required	Required	Required if above PEL for 30+ days/year	Required if above PEL for 30+ days/year
Training	Specialized (additional hours)	Specialized	Awareness (16 hours)	Awareness (2 hours)

Monitoring Requirements

Condition	Requirement
Class I and II (no NEA)	Personal monitoring representative of 8-hour TWA and 30-min excursion for each employee
Class I and II (with NEA)	May discontinue monitoring; must resume if conditions change
Class III and IV	Initial exposure assessment; monitoring if assessment indicates potential to exceed PEL
Results reporting	Within 15 working days to affected employees
Additional monitoring	Required whenever work practices, controls, or conditions change

Recordkeeping

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

Resources

29 CFR 1926.1101 - Full construction standard
29 CFR 1910.1001 - Full general industry standard
OSHA Asbestos Overview
Asbestos Air Monitoring During Abatement and Demolition - Detailed monitoring guidance
Ohio Asbestos Regulations Overview - Ohio-specific requirements
AHERA Sampling and the 1% Threshold
Asbestos NESHAP Explained