Analyzing an Air Sample: What is involved?

25 Mar Analyzing an Air Sample: What is involved?

In April 2016, the Occupational Safety and Health Administration (OSHA) passed brand-new guideline limits to protect workers from exposure to Respirable Crystalline Silica (RCS) in the work environment. These guidelines reinforced the need for industrial air sampling in the workplace.  Nanozen invented the DustCount 8899 to create a much more effective means to do real-time dust particle monitoring. 

The device is smaller, and more efficient and can save workers damage to their lungs by providing a viable solution to meet the OSHA guidelines.  Because the filter cassette can be removed and sent to a lab for analysis, the unit provides a mechanism to determine indoor air quality and keep the worker safe.  Let’s face it; no worker wants to see the Industrial Hygienist coming their way to do air sampling carrying a big machine they have to wear for 12 hours.

Use an Accredited Laboratory

The laboratory doing the air sampling analysis should be ISO 17025 accredited by an ISO 17011 accreditated organization.  The laboratory should offer analysis of both total and respirable RCS in both air and bulk materials.

The laboratory should use one of the National Institute for Occupational Safety and Health (NIOSH) following direct-reading methodologies:

X-ray Diffractor (XRD) in the Advanced Materials Laboratory at the Center for Advanced Energy Studies (CAES).

X-ray Diffractor (XRD) in the Advanced Materials Laboratory at the Center for Advanced Energy Studies (CAES).

The laboratory should also be able to identify interferences in the data.  It will help the laboratory by knowing what could be in the sample such as mica or feldspars from a mine.  The laboratory should be able to do a full scan by X-ray diffraction (XRD) and characterization analysis.

Some laboratories utilize the “ashing” technique (asher, muffle furnace, or plasma ashing) to measure RCS.  NIOSH supports this method as being effective in obtaining accurate results from air filter cassettes.

OSHA Appendix A

The laboratory should meet the requirements in Appendix A including

  • 29 CFR 1910.1053, Occupational Safety and Health Standards, 1910 Subpart Z, Respirable crystalline silica
  • 29 CFR 1926.1153, Safety and Health Regulations for Construction, 1926 Subpart Z, Respirable crystalline silica

The laboratory should calibrate against a National Institute of Standards and Technology (NIST) or NIST traceable standard material.  The calibration of the laboratory analysis equipment is performed with NIST standards for respirable fraction.  The NIST SRM 1878a (Certification of Standard Reference Material), SRM 1878b (Respirable Alpha Quartz) and SRM 1879a (Respirable Cristobalite) are needed.  A verification scheme protocol needs to be in place at the laboratory.

The lab should have an Internal Quality Control (QC) program evaluating uncertainty and provide an estimate of SAE to customers Consistent with an AIHA Laboratory Accreditation Programs (LAP) policy.

The following are some of the RCS sample analysis guidance from OSHA Appendix A.

Section Classification Requirement Guidance
5 Analysis Identifying polymorphs of respirable silica present. Identify any interfering materials and make appropriate corrections Infrared (IR) is acceptable for known matrices. The laboratory must have characterization data on each sample to minimize interferences.
5 Analysis Quantitative analysis of crystalline silica correcting for interferences, as needed The analysis should be consistent with lab LAP policies in place
6.1 Analysis Instrument calibration checks with silica standards bracketing the sample concentrations The analysis should be consistent with lab LAP policies in place
6.1 Analysis Every day in which samples are analyzed the lab must perform instrument calibration checks according to standards.  The samples are bracketed to report the sample concentrations Daily Reporting Limit (RL) sample and Continuing Calibration Verification (CCV) (if at the mid-point) may not meet this requirement.
6.2 Analysis Use at least a 5-point calibration curve The LAP will inform the lab as to the details of these requirements.
6.3 Analysis Provide a quantitative limit of detection representing a value no higher than 25% of PEL based on air volume The lab must demonstrate that its reporting limit is ten micrograms. The laboratory must have an RL of ten micrograms to meet 25% detection limit based on an 8-hr Time Weighted Average (TWA) PEL

This blog was written by Linda Rawson, who is the founder of DynaGrace Enterprises (dynagrace.com), an authorized distributor of the Nanozen DustCount 8899.  For further information, please connect with Linda on LinkedIn, or contact her at (800) 676-0058 ext 101.

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