Combustible gas detectors have been around for a long time, and failures associated with these instruments can have catastrophic consequences. Standards for the performance, selection, installation, use, and maintenance of combustible gas detectors have, therefore, also been around for a long time. These standards have been agreed to internationally through the relevant committee of the International Electrotechnical Commission. IEC Technical Committee 31, Equipment for Explosive Atmospheres, has published standards such as Explosive Atmospheres - Part 29-1: Gas Detectors - Performance Requirements of Detectors for Flammable Gases, and Explosive Atmospheres - Part 29-2: Gas Detectors - Selection, Installation, Use and Maintenance of Detectors for Flammable Gases and Oxygen. In general, these standards have focused on fixed-point detection systems for workplace safety rather than portable systems, but the similarities between these technologies allow for standards that apply to both. As new measurement technologies are developed, electrochemical and related sensors for gases and vapors have become more durable, selective, and sensitive, such that they can be used in workplace safety and health protection systems. These sensors are often sold in packages alongside combustible gas and oxygen detectors as (for example) “four-gas monitors.” The development of standards is now under way for detectors of toxic gases and vapors.

EUROPEAN STANDARDS The first standards addressing portable electrical detectors for toxic gases and vapors were developed in the European Union by a Joint Working Group of the European Committee for Standardization (CEN) and the European Committee for Electrotechnical Standardization (CENELEC). This working group produced a four-part standard: EN 45544 (since revised in 2016), Workplace Atmospheres – Electrical Apparatus Used for the Direct Detection and Direct Concentration Measurement of Toxic Gases and Vapours - Part 1: General Requirements and Test Methods; Part 2: Performance Requirements for Apparatus Used for Measuring Concentrations in the Region of Limit Values; Part 3: Performance Requirements for Apparatus Used for Measuring Concentrations Well Above Limit Values; and Part 4: Guide for Selection, Installation, Use and Maintenance. This standard incorporated performance uncertainty requirements from another CEN standard, EN482, Workplace Exposure – General Requirements for the Performance of Procedures for the Measurement of Chemical Agents. OTHER NATIONAL STANDARDS However, once the CEN/CENELEC Joint Working Group had done its job, it became clear that other national standards existed around the world. These standards included:
  • ANSI/ISA-92.00.01-2010, Performance Requirements for Toxic Gas Detectors and ANSI/ISA 92.00.02-2013, Installation, Operation, and Maintenance of Toxic Gas-Detection Instruments, developed by the International Society for Automation and published as American National Standards
  • UL 2075, Gas and Vapor Detectors and Sensors from Underwriters Laboratories (now UL, LLC)
  • CAN/ULC-S588, Standard for Gas and Vapour Detectors and Sensors, Including Accessories (a Canadian standard)
  • AS/NZS 4641:2007, Electrical Apparatus for the Detection of Oxygen and Other Gases and Vapours at Toxic Levels – General Requirements and Test Methods (a standard in Australia/New Zealand)
  • ASTM E2885, Standard Specification for Handheld Point Chemical Vapor Detectors (HPCVD) for Homeland Security Application, developed by ASTM International
In addition, U.S. NIOSH has published a Technical Report 2012-162: Components for Evaluation of Direct-Reading Monitors for Gases and Vapors (as well as an addendum, Hazard Detection in First Responder Environments). This technical report also provides performance tests. The “precision and accuracy” concept used by NIOSH is generally equivalent to the “expanded” uncertainty used in EN482.  INTERNATIONAL HARMONIZATION International cooperation on standards is important for creating a level playing field in commerce, to allow manufacturing and sales to be unencumbered by the necessity of meeting proliferating national and regional standards. At the time the EN standards were undergoing revision and the NIOSH technical report was published, I recommended the revival of a Working Group on Gases within the International Organization for Standardization. This Working Group existed within the Workplace Atmospheres subcommittee of ISO’s Technical Committee 146 on Air Quality. Thanks to existing agreements between ISO, CEN, and IEC, it was relatively simple to replace a regional CEN/CENELEC Joint Working Group with an international equivalent, Joint Working Group 45, which drew members from both ISO TC 146 SC 2 WG3 and IEC TC 31 MT 60079-29. Since the greater expertise lay within the IEC body, it naturally became the lead, with the convenor (a position similar to that of chair) and secretary being drawn from IEC.
RESOURCES AIHA: “Reporting Specifications for Electronic Real Time Gas and Vapor Detection Equipment” (PDF, October 2016). Atmosphere: “Interpreting Mobile and Handheld Air Quality Sensor Readings in Relation to Air Quality Standards and Health Effect Reference Values: Tackling the Challenges” (October 2017). The Synergist: “Purchasing the Best Instrument: How to Use the AIHA Standardized Equipment Specification Sheet” (June 2017).
The official roster of JWG 45 includes 27 participants from IEC representing 13 countries and 20 participants from ISO representing seven countries. (These numbers include individuals who belong to both organizations, and some who are not active.) Meetings have been held in the U.S., Canada, Germany, Russia, Belarus, Croatia, and Australia, generally in connection with the parent committee’s meetings (IEC TC 31). Unfortunately, there has been no ISO participation in meetings outside North America and Europe. The last meeting was held at AIHA headquarters in Falls Church, Va., in October, while the next meeting will be in October or November 2019. Two standards are at advanced ballot stages under the JWG 45: IEC/ISO 62990, Workplace Atmospheres – Gas Detectors – Part 1: Performance Requirements for Detectors for Toxic Gases and Vapours, and IEC/ISO 62990, Workplace Atmospheres – Gas Detectors – Part 2: Selection, Installation, Use and Maintenance of Detectors for Toxic Gases and Vapours. These standards classify two types of detector:
  • Type SM (safety monitoring) “general gas detection” equipment: for general gas detection applications (for example, safety warning, leak detection), where the performance requirements are focused on alarm signaling and the measuring range is defined by the manufacturer. 
  • Type HM (health monitoring) “occupational exposure” equipment: for occupational exposure measurement, where the performance requirements are focused on the uncertainty of measurement of gas concentrations related to occupational exposure limit values.
Part 1 of IEC/ISO 62990 is ready for its Final Draft International Standard ballot. No technical changes are allowed at this time: member countries are required to vote affirmative, negative, or abstain, a plurality of affirmatives will carry the day, and, if approved, the standard will be published until a new work item to modify, withdraw, or replace is undertaken. Part 2 will go out for its Draft International Standard ballot, and comments from this ballot will be addressed at the next meeting. The JWG includes two commercial test laboratories (Factories Mutual in Rhode Island and DEKRA EXAM in Bochum, Germany) that assisted with developing the procedures and designing the equipment for testing the detectors. It was very important that the tests in these standards not be so exacting that no equipment could ever pass them, nor so expensive as to effectively prevent their adoption. When final, these new standards will help inform the revision of AIHA’s Field Use of Direct Reading Instruments Body of Knowledge and the Field Use of Direct Reading Instruments certificate program. MAKING USE OF STANDARDS How can these standards be used by our IH community? As with all standards, the end-users must be aware of them and ask vendors or other parties to make use of them. Of course, regulators could compel the use of performance standards through regulation. After all, if a ladder must meet federal requirements, shouldn’t a toxic gas detector?  A subtler but equally effective path is for a customer to include a requirement for testing and certification as part of the sales contract. To help customers make knowledgeable purchasing decisions, AIHA’s Real-Time Detection Systems Committee has spent much effort developing Standardized Equipment Specification Sheet forms. The Committee created two SESS forms: one for instruments, and one for sensors. Each SESS form includes performance metrics, which are aligned with the NIOSH Technical Report tests, and which have their equivalents in the IEC/ISO standard tests. SESS forms are intended to be completed by instrument manufacturers at the request of anyone interested in purchasing a meter. Manufacturers could slot the results of their performance testing right into the SESS and could indicate the standards against which any piece of equipment was tested.  The SESS forms (version 2.0) can be downloaded from the Real-Time Detection Systems Committee website. Also available is a SESS manual that explains in detail how to use the forms. (For more information, read Patrick Owens’ article “Purchasing the Best Instrument” in the June/July 2017 issue of The Synergist.) IT’S NOT JUST THE WORKPLACE In addition to the use of sensors in workplace air monitoring, there has been substantial promotion of sensors for use in ambient air through “citizen science” projects. Sensors for typical ambient air pollutants such as particulate matter, carbon monoxide, and ozone are being produced cheaply, and miniature, wearable devices containing multiple sensors are now available. The National Institute for Environmental Health Sciences and EPA have a considerable interest in these instruments, especially as tools to be used in meeting the goals for Exposure Science in the 21st Century, an inter-agency effort to identify efficiencies and opportunities to collaborate in exposure science. One difference between instruments for occupational use and those for environmental applications is that guidance on interpreting the output of environmental sensors may not be readily available. As these sensors continue to proliferate, questions regarding the significance of high readings will likely be fielded by local environmental and health departments, whose staff probably have limited technical expertise. The provision of training and educational resources for these individuals will be critical.  Performance standards are also necessary for confirming the accuracy and reliability of these products. In August 2018, ASTM International initiated standard WK64899, Performance Evaluation of Ambient Air Quality Sensors and Other Sensor-based Instruments, and EPA is likely to participate. An ASTM subcommittee on Indoor Air Quality also has a new work item, WK62732, Performance Evaluation of Consumer-Grade Indoor Air Quality Sensors and Sensing Devices. In addition, Newport Partners, LLC, alongside researchers at the South Coast Air Quality Management District of California, is involved in new work items to characterize monitors for specific issues, such as carbon dioxide and PM2.5 indoor air sensors, for submission as ASTM standards. It is almost certain that similar initiatives exist in Europe. Is this “déjà vu all over again”? Is it time for a new Joint Working Group?   MARTIN HARPER, PhD, CIH, FAIHA, CChem, FRSC, is director of Scientific Research, Zefon International Inc., in Ocala, Fla., and courtesy professor, Department of Environmental Engineering Sciences, University of Florida, Gainesville, Fla. Send feedback to The Synergist.

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International cooperation on standards is important for creating a level playing field in commerce, to allow manufacturing and sales to be unencumbered by the necessity of meeting proliferating national and regional standards.
Gas Detection Standards Development: Call for Participants A new convener of ISO TC 146 SC2 WG3 is being balloted, who, if approved, will represent ISO on Joint Working Group 45 in the future. Should any U.S. readers of this article wish to participate, either through IEC or ISO, please contact Martin Harper

Standards for Direct-Reading Instruments for Toxic Gases and Vapors
BY MARTIN HARPER


Leveling the Field
Although the print version of The Synergist indicated The IAQ Investigator's Guide, 3rd edition, was already published, it isn't quite ready yet. We will be sure to let readers know when the Guide is available for purchase in the AIHA Marketplace.
 
My apologies for the error.
 
- Ed Rutkowski, Synergist editor
Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers