Asbestos Air Testing Lab Houston, TX — PCM by NIOSH 7400
Phase Contrast Microscopy fiber counting for OSHA personal exposure monitoring, area sampling and containment verification. Results reported in fibers per cubic centimeter and compared directly against the OSHA PEL of 0.1 f/cc. Analyzed in-house at 10200 East Freeway, Houston TX 77029 — samples received before 2:00 PM CT logged same day, 1-day rush available.
Why accredited PCM monitoring protects your crew
OSHA Requires the Assessment
29 CFR 1926.1101 requires an initial exposure assessment for Class I–IV asbestos work, and 1910.1001 applies the same PEL to general industry maintenance. Without PCM data there is no assessment.
It Proves the Controls Work
Negative pressure enclosures, HEPA filtration and wet methods are only as good as the numbers behind them. Area samples inside and outside containment document that the engineering controls are actually holding.
Speed Is the Service
An exposure result a week late tells you what happened, not what to do. PCM is a fast analysis and we price rush accordingly — the decision it informs is usually the next shift.
Know What It Does Not Say
PCM counts fibers by dimension, not by mineral. A high count in a fiberglass environment may contain no asbestos at all. We say so on the report rather than let the number imply more than it can carry.
OSHA Exposure Monitoring for All 50 States
Personal exposure monitoring is the most portable asbestos service we run, because the standard behind it is federal. The OSHA PEL is 0.1 f/cc in every state, and cassettes ship overnight from anywhere in the country.
The OSHA PEL Is Federal
29 CFR 1926.1101 and 1910.1001 apply nationally. The PEL and the excursion limit are identical in every state, so a personal exposure result means the same thing in Houston as in Ohio.
A Genuinely National Service
Because personal industrial-hygiene monitoring is federally regulated, states generally do not layer their own lab licensing onto it — New York's ELAP, for one, expressly does not certify laboratories for personal IH monitoring on that basis.
Accredited to ISO/IEC 17025
NIOSH 7400 fiber counting sits within our AIHA-LAP scope (LAP-101470) and our PJLA accreditation (137751). Both bodies are ILAC-MRA signatories.
Overnight From Anywhere
Free cassette kits with field blanks ship nationwide. Cassettes received before 2:00 PM CT are logged the same day, and PCM is fast enough that 1-day rush results are genuinely available.
Area and clearance sampling are a different matter
Personal OSHA exposure monitoring travels well. Clearance does not. Several states require a laboratory to hold their own asbestos credential before analyzing area or clearance air samples originating there — including New York, Pennsylvania (and the City of Philadelphia separately), Massachusetts, Vermont, Connecticut, Rhode Island, Maine, Virginia, West Virginia, Hawaii and Louisiana — and some also require the person collecting the sample to be state-licensed. We hold the Texas DSHS license (#300529). If your samples are area or clearance rather than personal exposure, tell us the state first and see clearance testing.
What PCM Asbestos Air Testing Measures
PCM counts fibers collected on a filter from a known volume of air and reports a concentration in fibers per cubic centimeter (f/cc). It is the OSHA-referenced method for asbestos exposure monitoring, and it is the analysis you use when the question is not is there asbestos in this material but how much is in the air right now, and is anyone over the limit.
Air sampling is required whenever workers disturb asbestos-containing material — abatement, demolition, maintenance on thermal system insulation, gasket work, mechanical tear-off of asbestos-containing roofing. It runs alongside the containment: personal samples on the crew, area samples inside and outside the enclosure. To identify the material before work starts, see PLM bulk analysis.
- Personal exposure monitoring — breathing zone, task or full shift
- Area monitoring inside containment, at the negative-pressure exhaust and in adjacent occupied space
- Excursion sampling against the 30-minute 1.0 f/cc limit
- NIOSH 7400 A rules by default, B rules on request
- Analytical sensitivity stated on every report alongside the result
- Analyzed in-house by TX DSHS-licensed microscopists — no send-outs
Who does what
AGT Labs is an analytical laboratory. Your EHS team, your consultant or your abatement contractor runs the pumps and collects the cassettes; we analyze them. We do not visit sites or perform field sampling. We supply the media, the protocol and the accredited analysis.
What PCM Cannot Tell You
Most laboratories leave this out. It matters enough to your data interpretation that we put it on the page.
PCM counts fibers. It does not identify them.
Under phase contrast, an asbestos fiber, a fiberglass fiber and a cellulose fiber of similar dimensions all count identically. The method counts anything longer than 5 µm with an aspect ratio of 3:1 or greater, regardless of what it is made of.
High-background environments
Insulation work, fiberglass handling, fresh drywall dust and mineral wool all generate countable fibers. In those settings a PCM result can read high with no asbestos present at all. Interpret the number against what else is airborne on that job.
Why PCM is still the right method
The OSHA PEL is itself written in PCM fiber counts. Substituting a more specific method does not produce a number comparable to the limit. For compliance monitoring, PCM by NIOSH 7400 is both the correct and the legally referenced analysis.
NIOSH 7400 — A Rules and B Rules
NIOSH 7400 defines two counting conventions, and which one your report uses changes the number. Specify it on the chain of custody — it cannot be applied retrospectively after the count.
| Convention | Counting criteria | Used for | Default? |
|---|---|---|---|
| A rules | All fibers longer than 5 µm with aspect ratio ≥ 3:1 | OSHA compliance monitoring — the convention the PEL is written against | Yes |
| B rules | Narrower criteria with restricted fiber dimensions | Specific research and inter-method comparison applications | On request |
A Rules — NIOSH Counting Convention
A Rules count any fiber that meets the dimensional criteria: longer than 5 micrometers, with a length-to-width ratio of at least 3:1, and a diameter less than 3 micrometers. Fibers touching or crossing the Walton-Beckett graticule boundary are counted as one-half if one end is inside the circle. Fibers that split or branch are counted as one fiber if they share a common junction point within the graticule area. Bundles of fibers where individual fibers cannot be resolved are counted as a single fiber. A Rules are the standard counting convention for OSHA compliance monitoring in the United States and produce the fiber counts used to compare against the 0.1 f/cc PEL.
B Rules — WHO Counting Convention
B Rules apply the same dimensional criteria as A Rules but differ in boundary handling. Only fibers with at least one end within the graticule circle are counted — fibers with both ends outside the circle, even if they cross through it, are excluded. B Rules also exclude fibers that touch particles larger than 3 micrometers. B Rules generally produce lower fiber counts than A Rules and are used in international monitoring programs aligned with World Health Organization guidelines.
Which Counting Rule to Specify
When requesting PCM analysis, specify which counting rule your project requires on the chain-of-custody form. AGT Labs defaults to NIOSH 7400 A Rules for domestic OSHA compliance monitoring. If your project involves international standards, EPA protocols, or specific contract requirements that call for B Rules, note this clearly. Reports identify the counting rule applied to each sample so your data is defensible under the applicable regulatory framework.
Default behavior
Unless you specify otherwise on the COC, we count by A rules and state the convention on the report alongside the result and the analytical sensitivity achieved. If your project protocol requires B rules, mark it clearly on the chain of custody before shipping.
PCM Sampling Media, Flow Rates & Volumes
Get these right and every sample produces a countable filter. Get the volume wrong and the sample is lost. Step-by-step in the field: how to collect asbestos air samples for PCM.
Pump Calibration & Cassette Handling — Field Best Practices
Accurate PCM results depend as much on field technique as laboratory analysis.
Sampling pump calibration must be performed before and after each sampling period using a primary calibration standard — either a soap-bubble burette or an electronic flow calibrator such as a DryCal or Defender. Set the pump flow rate within the range specified for the cassette diameter being used: 0.5 to 16 liters per minute for standard 25 mm cassettes, with most industrial hygiene applications targeting 1 to 5 L/min for personal monitoring. Record both pre-sampling and post-sampling flow rates; if they differ by more than 5%, the sample may be invalidated. Calculate the total sample volume by averaging the two flow rates and multiplying by the sampling duration in minutes.
Handle MCE filter cassettes with care to prevent fiber loss or contamination. Remove the cassette from its sealed bag only immediately before sampling. Remove the inlet and outlet plugs, attach the cassette to the pump tubing with the inlet facing outward (away from the worker’s body for area samples, or upward on the lapel clip for personal samples). Do not touch the filter surface or allow the open cassette to contact any surface. Position personal samplers in the worker’s breathing zone — within a 10-inch hemisphere centered on the nose and mouth — with the inlet facing downward at a slight angle to prevent gravitational settling of large particles onto the filter face.
After sampling, replace both plugs, seal the cassette in a labeled bag, and record the sample identification number, date, start and stop times, flow rates, worker name or area designation, and description of activities performed during the sampling period. Ship samples vertically in a rigid container to prevent filter damage during transit. Include at least two field blanks — unopened cassettes from the same lot carried to and from the sampling site — with every sample set for quality assurance purposes.
OSHA PEL & Excursion Limit — Comparing Your Result
Both the construction standard and the general industry standard carry the same limits, and both require an initial exposure assessment.
| Limit | Value | Averaging period | Citation |
|---|---|---|---|
| Permissible Exposure Limit (PEL) | 0.1 f/cc | 8-hour TWA | 29 CFR 1926.1101 · 1910.1001 |
| Excursion Limit (EL) | 1.0 f/cc | 30 minutes | 29 CFR 1926.1101 · 1910.1001 |
How the comparison is reported
Every report states the fiber concentration, the volume sampled, the analytical sensitivity achieved and a direct comparison against the PEL. Where the sample period is shorter than the shift, the report gives the concentration for the period sampled — the 8-hour TWA calculation depends on the rest of the shift, which is yours to apply.
Reading Your PCM Report — Fiber Counts, Detection Limits & Action Triggers
Understanding what each number means and what action it triggers under OSHA and EPA regulations.
PCM results are reported in fibers per cubic centimeter of air (f/cc), calculated by dividing the total fiber count by the volume of air sampled. The NIOSH 7400 method reports a limit of detection (LOD) that depends on the number of fields counted and the volume of air sampled — for a typical 960-liter sample (8 hours at 2 L/min), the LOD is approximately 0.01 f/cc when 100 fields are counted.
The key regulatory thresholds that determine your next steps are as follows. Results below 0.01 f/cc are at or below the analytical detection limit, indicating no measurable asbestos fiber exposure. Results between 0.01 and 0.05 f/cc represent detectable but low exposure — below OSHA’s action level, no additional monitoring is required, but results should be documented in exposure records. Results at or above 0.1 f/cc exceed the OSHA PEL and require immediate corrective action: engineering controls, respiratory protection, medical surveillance, regulated area establishment, and written compliance programs. Results above 1.0 f/cc indicate a significant exceedance requiring immediate work stoppage, area isolation, and implementation of emergency controls.
For abatement clearance monitoring, the threshold depends on the applicable regulation. Under OSHA, clearance is based on a PCM result below 0.01 f/cc (or the analytical LOD). Under EPA AHERA for school buildings, clearance requires that the average of five indoor samples not exceed the average of five outdoor (background) samples, or not exceed 0.01 f/cc, whichever is higher. Some state and local regulations specify different clearance thresholds — Texas does not have a separate state asbestos clearance standard beyond the federal requirements, but local jurisdictions may apply additional criteria.
AGT Labs reports all results with the applicable LOD, the sample volume, fiber density per square millimeter, and the calculated airborne concentration so your project team can evaluate compliance against any applicable standard.
Personal vs Area PCM Monitoring
Different questions, different placement, different evidentiary weight. On an active abatement you run both.
Personal Monitoring
Pump on the worker, cassette in the breathing zone, run for the task or the shift. This is what OSHA compliance is judged on, and the only sample type that documents an individual's exposure. Required for the initial exposure assessment.
Area Monitoring
Fixed-location samples. Inside containment they show whether engineering controls are holding; outside containment and at the perimeter they document that adjacent occupied areas were not affected. Area results do not substitute for personal samples in a compliance record.
Clearance Sampling
After the work, against a different criterion and a different protocol — aggressive sampling, higher volumes, a written pass/fail determination. It is PCM analysis, but a different service with its own requirements.
Which PCM sample type does your job need?
Every PCM Analysis, Every Standard, Every Deliverable
What each PCM sample type returns, side by side.
| Analysis Type | Method / Standard | Sample Media | Report Deliverable | Rush? |
|---|---|---|---|---|
| PCM Personal Air Monitoring | NIOSH 7400 (A & B rules) | 25 mm MCE cassette (0.8 µm) | f/cc + OSHA PEL comparison + analytical sensitivity | Yes |
| PCM Area Air Monitoring | NIOSH 7400 (A & B rules) | 25 mm MCE cassette (0.8 µm) | f/cc by location + containment comparison | Yes |
| PCM Excursion Sampling | NIOSH 7400 · 30-minute period | 25 mm MCE cassette (0.8 µm) | f/cc + 1.0 f/cc excursion limit comparison | Yes |
| PCM Field Blanks | NIOSH 7400 QA requirement | 25 mm MCE cassette (0.8 µm) | Blank count, reported with the batch | Yes |
Accredited Method Scope
AGT Labs performs PCM asbestos air analysis by NIOSH 7400, accredited under AIHA IHLAP (LAP-101470) and PJLA ISO/IEC 17025:2017 + DoD-ELAP (No. 137751, Certificate L26-747), and licensed by Texas DSHS (#300529). Analysis uses phase contrast microscopy at approximately 400× magnification with a Walton-Beckett graticule, applying the A or B counting rules your project specifies. Other fiber-counting procedures, such as OSHA ID-160 or ISO 8672, are not on our accredited scope.
What Every Certified Report Includes
Every certified report from AGT Labs includes the elements required by each applicable standard: laboratory and analyst identification, lab accreditation number, sample identification cross-referenced to your chain-of-custody form, date of analysis, analytical method used, counting rule applied, fiber density, sample volume, calculated airborne fiber concentration, limit of detection, field blank results, and any qualifications that affect data interpretation. Reports are available in PDF format through our secure online portal, with original signed copies mailed on request. For large monitoring programs, we provide bulk data exports in CSV format compatible with industrial hygiene database software.
What is on every report
Method reference and counting convention, fiber concentration in f/cc, volume sampled, analytical sensitivity achieved, direct PEL comparison, analyst signature, QA/QC sign-off, and the accreditation numbers the result rests on. Delivered through a secure portal and accepted by OSHA, TX DSHS and PJLA-accredited programs.
PCM Turnaround Times & Free Cassette Kits
PCM is a fast analysis and 1-day rush is available — most exposure decisions cannot wait a week.
Free PCM Air Sampling Kit Includes
- 25 mm MCE cassettes, 0.8 µm, with 50 mm conductive cowls
- Field blank cassettes to meet the 10% QA requirement
- Lot-certified, calibration-traceable media documentation
- Pre-numbered Asbestos Chain of Custody form
- Flow rate and volume reference card
- Pre-paid UPS return shipping label (domestic)
Kits ship via UPS Ground — order with 5 business days notice. Houston metro courier pickup available: (713) 453-6090.
From Cassette to Certified PCM Report
Request Kit or COC
Free PCM kits ship with 5 business days notice, or use your own lot-certified MCE cassettes.
Calibrate & Sample
Calibrate the pump, record the flow rate, sample to volume. Watch the filter loading in dusty work.
Blanks & COC
Open your field blanks 30 seconds, seal, label as blanks. Record flow, start and stop times per cassette.
Ship Same Day
Caps on, upright, tamper-evident outer bag. Received before 2:00 PM CT logs the same day.
Counted & Reported
Counted by TX DSHS-licensed microscopists in Houston, QA reviewed, delivered with the PEL comparison.
Lab-Side Filter Preparation
For PCM preparation, the analyst opens the cassette in a clean preparation area, removes the MCE filter, and clears it using the acetone-triacetin method. A wedge-shaped section of the filter is cut and mounted on a glass slide with triacetin, which renders the filter transparent while preserving fiber positions. The cleared slide is placed under the phase contrast microscope equipped with a 10× eyepiece and 40× positive-phase objective (total magnification approximately 400×). The analyst verifies optical alignment using an HSE/NPL phase contrast test slide, confirming that the microscope resolves the appropriate set of test blocks before counting begins.
Fiber Counting Procedure
Fiber counting follows a systematic field-by-field traverse of the filter. The analyst counts a minimum of 20 fields, continuing until either 100 fibers are counted or 100 fields are examined — whichever comes first. If the fiber density exceeds 10 fibers per field, the analyst notes that the filter is overloaded and reports the result with a qualification noting that the reported concentration may underestimate actual exposure. Field blanks are analyzed alongside project samples to establish baseline fiber contamination; if blank results exceed 7 fibers per 100 fields, all associated sample results are flagged.
Certified Report Contents
The final report includes the fiber density per square millimeter of filter area, the calculated airborne concentration in f/cc, the number of fields counted, the volume of air sampled, the counting rule applied (A or B), the analytical sensitivity (LOD), and any qualifications or observations that affect data interpretation. Reports are reviewed and signed by an analyst who meets NIOSH 582 or equivalent training requirements, and released through our accredited quality system.
Who runs the pumps
You, your consultant or your abatement contractor. AGT Labs does not visit sites or perform field sampling. We supply the media, the flow-rate and volume protocol, and the accredited analysis — the sampling plan and the pumps are yours.
PCM Asbestos Air Testing — Frequently Asked Questions
Answered by the accredited microscopists who run the counts.
What is PCM asbestos air testing?
Does a PCM result prove the fibers were asbestos?
What is the difference between NIOSH 7400 A rules and B rules?
What is the OSHA PEL for asbestos?
What volume should I sample for PCM?
What flow rate should I use?
Can I use my own cassettes?
How many field blanks do I need?
Is PCM accredited at AGT Labs?
Do I need PCM or PLM?
How fast can I get PCM results?
Who collects the air samples?
Need PCM Air Samples Counted?
AIHA-LAP LAP-101470, PJLA 137751 and TX DSHS #300529. Free cassette kits, 1-day rush, results compared directly against the OSHA PEL.