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Does OSHA/MSHA Dust/Contaminant Sampling Produce Valid Evidence of Violations?

Given that dust and other contaminate sampling is highly technical (e.g. silica, lead, silver, arsenic, mercury and diesel exhaust), many employers are tempted to defer to the technical work done by the enforcement agencies. You shouldn’t.

Indeed, precisely because sampling and analysis is so technical, when enforcing exposure limits or related standards (e.g., engineering controls, respirator and medical exam mandates, hazard posting, and clean lunch and change rooms), the Mine Safety and Health Administration (MSHA) and the Occupational Safety and Health Administration (OSHA) face difficult burdens of proving the “accuracy” and “validity” of their exposure limit violations.

Employers should understand that agency sampling and analysis results are merely estimates, based on a series of presumptions. Whether or not they are valid depends on a number of factors, for which the agency itself often creates, controls and possesses the evidence. 

Asking the right questions of the agency, both during a citation challenge, and informally at the inspection opening conference, the start of sampling, or the closing conference) can provide you with important information to weigh the value of the sampling results or serve as evidence to defend against citations and penalties.

A simple Freedom of Information Act request letter also can help deliver critical information for assessing the validity of MSHA/OSHA sampling results. In contrast, accepting invalid agency results, even with small penalties, can cost more than you might think. It can provide evidence for more severe enforcement later and/or for lawsuit claims against employers. 

This article is the first of a planned series of three, addressing exposure limits and related citations. Our goal is to guide you through key evidence, based on a long history of cases handled by our safety and health law team. In those cases and in rulemaking comments, we’ve worked with some of the nation’s leading scientists, who explained that Industrial Hygiene (IH) is not just science; it’s also “art,” and that MSHA, OSHA and other agencies do not always succeed in trying to impose a “fine line” of non-compliance.

Here, we set forth a few initial questions/requests to pose to OSHA or MSHA regarding sample collection. In later articles, we will discuss sample analysis questions that also weigh heavily on accuracy and validity (e.g. how the laboratory calibrates its equipment, corrects for error factors, and complies with a slew of scientific norms and procedures). In our final article we will address the possible impacts and planning of company sponsored sampling and analysis.

Science: The Foundation for Strict Measurement Procedures

OSHA, MSHA, The National Institute for Occupational Safety and Health (NIOSH) and other agencies have adopted extensive, detailed procedures for IH sampling and analysis that “estimate” sample results, compare them to exposure limits, and account for accepted sampling and analytical error in making compliance decisions. Their failure to follow these procedures can be strong evidence that their results, at or above exposure limits, may be inaccurate and not valid evidence of overexposure.

Sample collection procedures generally are within the control of the field inspector, while lab analyses are within the control of the agency’s lab or analytical contractor. Generally, agency procedures for measurement and analysis are attempts to “estimate” personal exposures and compare them to regulatory exposure limits, intended to reduce risks and permit safe exposures.

For example, most dust measurements generally are limited to “respirable” size (very small) dust particles (e.g. less than 10 microns) that create a long-term risk of disease through their ability to penetrate to the lower regions of the lung and not be rejected by routine breathing.

The collection and analysis of “respirable” dust requires the use of an appropriate sampling cyclone, to separate airborne dust particles into respirable and non-respirable sizes, by using a calibrated pump to control air flow through the cyclone and sampler, and deposit the respirable portion onto a small filter that can be examined, weighed and analyzed at the lab.

An employer should request copies of all documents related to the samples collected at their site. Which documents should you look for? Your roadmap is each agency’s technical manual governing the particular sampling involved (for instance, OSHA has its Technical Manual, as well as a Chemical Sampling Information (CSI) file and Field Operations Manual).

The manuals describe each and every step required for agency sampling collection and analysis. Many of these steps require creating records. For example, the inspector should have records of the type cyclone used, the type and model number of the pump and calibration equipment used, and whether “[b]ulk samples are necessary” (e.g. to check for interfering minerals).

OSHA should also have “chain-of-custody” records to demonstrate the treatment of the sample throughout the process. OSHA/MSHA altered samples produced (for lab analysis ease), may not be valid samples for compliance determinations. Similarly, samples contaminated with oversized, non-respirable particles, may not be valid proof of exposure limit violations, based on respirable dust. All of these facts and many more create variability or error in analytical results that can be fatal to the validity of an agency sampling exercise.

For example, the OSHA Technical Manual states that certain pumps should not be calibrated with certain calibrators due to a high error rate: “The escort elf pumps should not be calibrated using the Bios International piston type calibrators because they can produce an uncertainty error of more than 4 percent (compared to the desired margin of error of ±1 percent).” (

The validity of your citation may hinge on whether the inspector did a proper calibration with the right calibrator, calibrated the pump at the same altitude before and after sampling, visually observed the sampling, and more. Each activity during the sampling and analysis process has its own error rate and adds variability. NIOSH accepted levels of variability are limited to +/-25 percent of the true value, 95 percent of the time. Weighing the filter, analyzing via x-ray diffraction, and other steps each add significant error or variability to the end result. Documented OSHA/MSHA errors or accepted variability exceedances question the validity of over exposure allegations and citations.

Consider these additional opportunities for error. For personal air sampling, did the inspector:

  • Assemble filter cassettes prior to the site visit?
  • Mix different brands of cassette components (a no-no)?
  • Ensure a good seal between the filter and the cassette?
  • Fully charge pump batteries?
  • Use the same specific type of sample media in line (e.g., filter, sorbent tube) that will be used for sampling in the field?
  • Use the same media for calibration and sampling (not appropriate)?
  • Calibrate sampling pumps at the same temperature and pressure (altitude) as the field sampling location?
  • Accurately and completely create sampling pump calibration records and field sampling notes using the OIS air sampling worksheet?
  • Take photographs and/or videos (as appropriate) and detailed notes?
  • Take ventilation and/or smoke tube measurements as helpful to assess engineering controls?
  • Observe whether the employee wore the sampling equipment properly and whether or not the employees sampled were performing their normal duties at the time?
  • Identify and document: what facility processes/operations were being run during sampling, what tasks the employee normally performed and how this shift was different, what materials employees were exposed to, and what were the normal work practices and deviations during that shift, what exposure controls were in place and how effective they were?
  • Conduct representative full-shift sampling (in the case of exposure limits that are 8-hour time-weighted averages)?

All of these factors have been observed in past OSHA inspection results as issues related to issued citations. It should be noted that these issues are only some of the many factors impacting accuracy and validity of IH sampling. But, sampling is only part of the agency challenge to measure your compliance.

As we will examine in an upcoming article, lab procedures are equally exacting and complicated, setting a high standard for the government to meet. Moreover, your own sampling and analysis results or that of your insurer or consultant may produce evidence that the agency may try to obtain and use to support their enforcement efforts. These issues also will be addressed as part of our planned series of articles aimed at providing tools for employers in meeting anticipated increasing agency enforcement efforts.

Henry Chajet is a partner at Husch Blackwell LLP. He provides strategic counsel to clients, to prevent or reduce risks from situations of crisis and uncertainty, in environmental, employee health and safety, and antitrust law matters. He also represents clients in rulemaking and legislative proceedings, as well as in investigations and litigation involving unfounded enforcement actions. Chajet is a member of Husch Blackwell’s Technology, Manufacturing & Transportation team.


Thomas A. Hall, Ph.D., CIH., FAIHAOR, is an industrial hygiene consulting professional based in Oklahoma City.