Performance-Specifications-for-Instrumentation-Systems

MS-PC 2015: Performance Specifications for Instrumentation Systems Designed to Measure Radon Gas in Air Page 2 of 20 Manufacturers and/or laboratories claiming that the device(s) they produce or use meet the requirements of this standard should maintain documentation supporting that claim; Section 8 p rovides a sample report template. Compliance with this standard does not constitute “certification” or “device approval,” such as from a national proficiency program. Hereafter, the term radon is used to mean specifically 222 Rn gas and thoron to mean specifically 220 Rn gas; the term radon progeny means the short-lived radioactive decay products of 222 Rn gas, and thoron progeny means the short-lived radioactive decay products of 220 Rn gas. A complementary standard, ANSI N42.50, Performance Specifications for Systems Designed to Measure Radon Progeny in Air (ANSI/IEEE N42.50), has been promulgated to address instrumentation for the measurement of radon progeny. This standard specifies minimum performance requirements for radon measuring devices, as well as testing criteria for demonstrating and documenting compliance. The tests are to be conducted in a STAR u nder various conditions of radon concentration, temperature and humidity. A manufacturer or laboratory that makes or uses a device or measurement system that is listed by a national radon proficiency program may already have results of testing on file that could partially or fully suffice to demonstrate compliance with this standard. For example, results of device exposures conducted in a STAR for device evaluation, quality control (spiking), performance testing, or in some cases calibrations, may be used to demonstrate compliance with this standard. Such exposures might not be conducted as blind tests, yet may be used to demonstrate compliance with this standard. Providers with multiple device types, or multiple models of the same device type, may test more than one type and/or model simultaneously. Once a manufacturer and/or laboratory has demonstrated that a device or measurement system complies with this standard, the testing procedure would only be required again if a significant change, as defined in Section 4, was made to the instrument or measurement system. The environmental conditions specified for the tests in a STAR are those likely to be found in an indoor environment where people may live or work. The standard does not consider outdoor or harsh environmental conditions. In this standard, the devices are categorized in the following way: “continuous,” “integrating” or “equilibrating.” These terms are defined in Section 4. This standard makes use of three different verbs, shall, should and may , to indicate the level of rigor with which a particular criterion is applied. For the purposes of this standard, these terms are defined in Section 4. 4 DEFINITIONS & ABBREVIATIONS Accuracy – the degree of agreement between the observed value ( X ) and the conventionally true value ( T ) of the quantity being measured. The degree of agreement is often expressed as the difference between X and T : ( X – T ), or as a percentage relative to T: (100 [ X – T ] / T ). Aged Air – air that has been stored and isolated for at least 30 days before use to allow the radon in it to decay to an insignificant concentration. As Constant as Practicable – this term is defined by agreement between the provider of the device(s) and the operator of the STAR, taking into consideration the inherent function of the device(s) and the design limitations and operational requirements o f the STAR. Atmosphere – gas intended to be monitored or sampled for radon. Bias – systematic or persistent distortion of a measurement process that causes errors in one direction. Bias is determined by measuring the positive or negative difference from the conventionally true value, often as a percentage of the conventionally true value.