back to OSHA Safety and Health Topics

Contents
Page last reviewed: 09/30/2009
Highlights
  • Exposure and Assessment Strategies Committee. American Industrial Hygiene Association (AIHA). AIHA provides leadership in exposure assessment and strategies for environmental health, safety, and industrial hygiene professionals.
Sampling and Analysis - Copyright WARNING: Not all materials on this Web site were created by the federal government. Some content  including both images and text  may be the copyrighted property of others and used by the DOL under a license. Such content generally is accompanied by a copyright notice. It is your responsibility to obtain any necessary permission from the owner's of such material prior to making use of it. You may contact the DOL for details on specific content, but we cannot guarantee the copyright status of such items. Please consult the U.S. Copyright Office at the Library of Congress  http://www.copyright.gov  to search for copyrighted materials.
Sampling and Analysis

Chemical sampling and analysis is used by occupational health and safety professionals to assess workplace contaminants and associated worker exposures. The validity of an assessment is based, in part, on the procedures used for sample collection and analysis, and data interpretation. In many instances these procedures use approaches that have been refined over many years and are accepted by the professionals as good practice. However, the multitude of variables within a specific workplace require the professional to exercise judgment in the design of a particular assessment.

Sampling and analysis hazards are addressed in specific standards for the general industry.

OSHA Standards

This section highlights OSHA standards and standard interpretations (official letters of interpretation of the standards) related to sampling and analysis.

Note: Twenty-five states, Puerto Rico and the Virgin Islands have OSHA-approved State Plans and have adopted their own standards and enforcement policies. For the most part, these States adopt standards that are identical to Federal OSHA. However, some States have adopted different standards applicable to this topic or may have different enforcement policies.

General Industry (29 CFR 1910)

Standard Interpretations

Sampling

Effective and efficient sampling strategies require planning and foresight to ensure the most productive and thorough evaluation of contaminants in the workplace. The following references provide information about chemical sampling.

Survey Protocol

Prior to conducting chemical sampling a survey protocol should be developed. This protocol serves as a guide in performing the survey. The amount of detail necessary will depend on the purpose of the survey and to whom the results will be submitted. At a minimum, the protocol should include the following:

  • Purpose of the survey. Why is the survey being conducted and what is the desired outcome? Background information such as previous surveys, operational or equipment changes should be referenced.

  • Where to sample. This identifies expected exposure sites. It is based on where chemicals are stored, transported, and used at the site, and what ventilation and airflow patterns exist.

  • What to sample. This is based on available information. What are the potential chemical hazards?

  • Who to sample. This is based on knowledge of the potential exposure sites and the various job requirements at the site. What job classifications or specific individuals should be considered for monitoring? Workers with the greatest potential for exposure must be included.

  • How many samples should be collected. Consider the number of exposure sites, job classifications, and potential chemical hazards. How many samples are necessary to assess the various exposure hazards?

  • How will the samples be collected and analyzed. After determining the potential hazards, what published methods are available, and which ones will provide the most meaningful data. Is there a potential for other chemical hazards in the area and should methods be considered which may provide screening information?

Chemical Sampling

Sampling Methods

Direct Reading

  • Direct reading instruments provide an excellent mechanism to monitor potential exposures. They allow significant amounts of data to be collected and the workers exposure profile during operations to be determined. They, also, provide qualitative data relative to worker exposures. However, they may not provide the necessary specificity, detection limit, or precision for compliance monitoring or exposure assessment.

Grab (detector tubes, gas bags)

Passive

Surface Contamination

  • Surface Contamination. OSHA Safety and Health Topics Page. Provides safety and health information related to surface contamination in the workplace.

Bulk samples

  • Bulk samples may be collected and shipped to the laboratory as an aid in assessing sources of contamination. In order to prevent contamination of personal samples, they should be kept separate from the personal samples when transporting and packaged in separate containers when shipping.

Analysis

Published analytical methods address several hundred possible workplace contaminants. However, these methods do not address all chemical hazards. The following references link to resources that provide analysis information on many chemical hazards.

Analytical Methods

Method Modification and Development

Published analytical methods address several hundred possible workplace contaminants. However, these methods do not address all chemical hazards. Some chemicals are so specialized that they are rarely encountered. New chemicals are constantly being developed. Other chemicals are not stable on existing sampling media. In these instances it becomes necessary to modify an existing method to accommodate the contaminant or a new method must be developed.

The procedures for method modification and development vary depending on the properties of the chemical, possible interferences, the desired sampling medium, the desired analytical technique, sensitivity required, and similar factors. Therefore, method modification and development should only be undertaken by an experienced analyst or researcher. However, the following are items which should be considered and answered by any method modification or development.

  • Can the analyte be collected by and removed from the sampling media?

  • What are the collection and recovery factors and are they acceptable?

  • Is the detection limit sufficiently low to provide meaningful data, especially when adjusted for collection and recovery factors?

  • Will expected interferences produce false positive, false negative, or biased results?

  • If possible, can the results be verified by comparison with an accepted procedure?

  • NIOSH Manual of Analytical Methods (NMAM). US Department of Health and Human Services (DHHS), National Institute for Occupational Safety and Health (NIOSH) Publication 2003-154, (2003). Provides individual analytical methods, listed by chemical name or method number.

Laboratory Selection

The selection of a laboratory is influenced by many factors. Among these are:

  • Does the laboratory perform the required analysis?

  • What are my requirements for quality assurance and does the laboratory quality assurance program meet these requirements?

  • Does the laboratory analyze samples and report results within my required turnaround time?

  • Does the analytical report contain the information I need?

  • Are detection limits reported and are they sufficiently low?

  • Are analytical costs acceptable?

  • Does the laboratory provide the client services I desire?

  • Am I confident in the results provided?

Laboratory Accreditation and Certification

Participation in accreditation and certification programs allow laboratories to compare themselves against other laboratories and against accepted standards. Most programs require participation in a performance evaluation testing program where samples of unknown concentration are analyzed and reported to an independent body. Many programs require an on-site assessment by a trained quality assessor. Successful participation in an accreditation or certification program is an indicator that a laboratory operates under a functioning quality assurance program. It does not guarantee that the results produced by the laboratory are beyond question.

Laboratory (Internal)

Laboratories analyzing samples should have a documented quality management system. This system should address topics such as:

  • Organization of the Management System

  • Control of Documents, Data and Records

  • Purchasing

  • Corrective and Preventive Action

  • Internal Audits

  • Selection and Training of Personnel

  • Selection of Analytical Methods

  • Quality Assurance and Estimation of Uncertainty

  • Equipment and Instrumentation

  • Traceability of Standards and Materials

  • Reporting of Results

Laboratory (External)

Laboratories performing industrial hygiene analyses should participate in external performance evaluation programs, and be subject to audit by external assessors. The appropriate accreditation and certification programs discussed above should be part of a laboratory's quality assurance program.

When submitting samples to a laboratory, there are several methods which can be easily used to assess the accuracy and precision of the laboratory's results. In all cases, if a problem is detected, it would be wise to assume that the error is in the external sample, unless other information indicates otherwise. Once a problem has been identified, the laboratory quality assurance manager should be contacted and the problem resolved to the satisfaction of all parties.

  • Collect two samples under the same conditions. Remember, when evaluating these samples, that the two samples are not identical. For instance, a droplet of solvent could be splashed onto one sample but not the second giving a false reading for the first sampler.

  • If the sample is a bulk material, divide it into two portions after thoroughly homogenizing. If the sample is not homogenized, the two portions could contain differing amounts of analyte.

  • Prepare "spiked" samples of known concentration to be submitted blind with field samples. These must be prepared by a skilled individual. Additional spikes should be prepared at the same time so that the spiking can be verified by a second laboratory if questionable results are reported.

Data Validation and Interpretation

When an employee is sampled and the results analyzed, the measured exposure will rarely be the same as the true exposure. This variation is due to sampling and analytical errors (SAE's). The total error depends on the combined effects of the contributing errors inherent in sampling, analysis, and pump flow.

Consider the following questions when analyzing results:

  • Do the results make sense?

  • Based on knowledge of the sampling site, are the laboratory results consistent with what you expect?

  • And are they consistent between samples?

  • Are the results consistent with previous sampling results?

  • If an error in analytical procedures or results is suspected, contact the laboratory quality assurance section for assistance and resolution.

  • Were the samples collected using the correct sampling method and were the method specifications followed?

  • Was the correct sampling media used?

  • Were the sample flow rates and total volumes within specifications?

  • Were samples properly preserved and shipped?

  • Was there a possibility of contamination? Were blanks submitted for analysis?

  • Were there any unusual circumstances surrounding the sample collection which may influence the validity?

Additional Information

Related Safety and Health Topics Pages

Training

Consultation Services

Other Resources

  • Methods for the Determination of Hazardous Substances (MDHS) guidance. Health and Safety Executive (HSE). HSE of Great Britain has developed methods which address analysis of workplace air samples.

  • American Society for Testing and Materials (ASTM) International. ASTM International provides standards that are accepted and used in research and development, product testing, quality systems, and commercial transactions around the globe. The following resources are ASTM technical committees.
    • Committee D22 on Air Quality. The areas of interest of this committee are ambient air, source emissions, workplace atmospheres, indoor air, meteorological measurements, sampling strategies, calibration procedures, quality assurance practices, and the development of international standards in these fields.
    • Committee E34 on Occupational Health and Safety. This committee's standards address the identification, exposure, symptomatology, treatment, control, and administrative aspects of diverse occupational safety and health issues such as silica, metalworking fluids, and ergonomics.

Accessibility Assistance: Contact the OSHA Directorate of Technical Support and Emergency Management at (202) 693-2300 for assistance accessing PDF materials.