Components for Evaluation of Direct-Reading Monitors for Gases and Vapors
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A NIOSH TECHNICAL REPORT Components for Evaluation of Direct-Reading Monitors for Gases and Vapors DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Institute for Occupational Safety and Health Components for Evaluation of Direct-Reading Monitors for Gases and Vapors DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Institute for Occupational Safety and Health This document is in the public domain and may be freely copied or reprinted. DISCLAIMER Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health (NIOSH). In addition, citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs or prod- ucts. Furthermore, NIOSH is not responsible for the content of these Web sites. All Web addresses referenced in this document were accessible as of the publication date. ORDERING INFORMATION To receive documents or other information about occupational safety and health topics, contact NIOSH at Telephone: 1–800–CDC–INFO (1–800–232–4636) TTY: 1–888–232–6348 E-mail: [email protected] or visit the NIOSH Web site at www.cdc.gov/niosh. For a monthly update on news at NIOSH, subscribe to NIOSH eNews by visiting www.cdc.gov/niosh/eNews. DHHS (NIOSH) Publication No. 2012–162 July 2012 ii Components for Evaluation of Direct Reading Monitors FOREWORD The Occupational Safety and Health Act of 1970 (Public Law 91–596) assures, insofar as possible, safe and healthful working conditions for every working man and woman in the Nation. The act charges the National Institute for Occupational Safety and Health (NIOSH) with recommending occupational safety and health standards and describing exposure concentrations that are safe for various periods of employment, including but not limited to the concentrations at which no worker will suffer diminished health, functional capacity, or life expectancy as a result of his or her work experience. Under that charge and by a 1974 contract, NIOSH and the Occupational Safety and Health Administration jointly undertook the evaluation of sampling and analytical methods for airborne contaminants to determine if current methods met the criterion to produce a result that fell within 25% of the true concentration 95% of the time. In 1995, that protocol was revised. This document expands the 1995 method development and evaluation experimental testing methods to direct-reading monitors for gases and vapors. It further refines the previous guide- lines by applying the most recent research technology and giving additional experimental designs that more fully evaluate monitor performance. These Components are provided for laboratory users, consensus standard setting bodies, and manufacturers of direct-reading instrumentation and are compatible with American National Standards Institute/International Society of Automation guidelines. They provide more simplified procedures to estimate the precision, bias, and accuracy of a monitor; to evaluate a monitor relative to the 25% accuracy criterion; and to demonstrate that an atmosphere is relatively safe. John Howard, M.D. Director National Institute for Occupational Safety and Health Centers for Disease Control and Prevention Components for Evaluation of Direct Reading Monitors iii ABSTRACT The Occupational Safety and Health Act of 1970 (Public Law 91–596) charged the National Insti- tute for Occupational Safety and Health (NIOSH) with the responsibility for the development and evaluation of sampling and analytical methods for workplace compliance determinations. Under that charge, NIOSH and the Occupational Safety and Health Administration jointly undertook the evaluation of sampling and analytical methods for airborne contaminants by contract in 1974 to determine if methods met the criterion to produce a result falling within 25% of the true concen- tration 95 times out of 100. The present document further expands the experiments used during the initial methods development and evaluation research to direct-reading monitors for gases and vapors. This document provides discussion of the physical, operational, and performance characteris- tics for direct-reading monitors. Guidance is provided for experiments to evaluate response time, calibration, stability, range, limit of measurement, impact of environmental effects, interferences, and reliability of direct-reading monitors. Also included are evaluation criteria for the experiments and details for the calculation of bias, precision and accuracy, and monitor uncertainty. PREFACE This Components document consists of a main section of three parts, citation of relevant ANSI/ISA standards, and references; eight appendices; and a bibliography. The main section presents back- ground information, reviews various monitor types, and suggests components for monitor evalu- ation. Appendices A–F assume a prerequisite knowledge of statistics and provide details for the statistical computations, including procedures for calculation of accuracy, bias, precision, alarm set points for alarm system monitors, and explanatory material for relating accuracy to uncertainty. Although all computations can be programmed in spreadsheets, use of a statistical software pack- age is highly recommended. Example computer code is given in Appendices A, B, and G for some of the statistical formulas. For the convenience of interested readers, the more complicated for- mulas, denoted by bracketed reference numbers, are presented as LaTeX versions in Appendix H. A companion Addendum document, published separately, expands the applicability of the Components by presenting methods to be used in evaluating direct-reading monitors for hazard detection in first-responder environments. Please direct comments, questions, or requests for additional information to the following: Director, Division of Applied Research and Technology National Institute for Occupational Safety and Health 4676 Columbia Parkway Cincinnati, OH 45226-1998 Telephone: 1-513-533-8462 or 1-800-CDC-INFO iv Components for Evaluation of Direct Reading Monitors CONTENTS DISCLAIMER ................................................................................................................................ ii ORDERING INFORMATION ....................................................................................................... ii FOREWORD ................................................................................................................................. iii ABSTRACT ................................................................................................................................... iv PREFACE ...................................................................................................................................... iv ABBREVIATIONS ........................................................................................................................ ix DEDICATION ............................................................................................................................... xi ACKNOWLEDGEMENTS ........................................................................................................... xi Part I. Direct-Reading Monitor Background Information ........................................................1 Introduction ..............................................................................................................................1 Definitions ................................................................................................................................2 Accuracy ..........................................................................................................................3 Precision ...........................................................................................................................4 Bias ..................................................................................................................................4 Limit of Detection and Limit of Measurement ................................................................5 Measurement Range .........................................................................................................5 Evaluation Range .............................................................................................................5 Interferences .....................................................................................................................5 Sampling Rate or Uptake Rate .........................................................................................5 Exposure Limit .................................................................................................................5 Linearity ...........................................................................................................................6 Response Time .................................................................................................................6 Sensitivity ........................................................................................................................6 Detector ............................................................................................................................6 Detector Life ....................................................................................................................6 Monitor Uncertainty .........................................................................................................7