Performance-Specifications-for-Instrumentation-Systems

MS-PC 2015: Performance Specifications for Instrumentation Systems Designed to Measure Radon Gas in Air Page 13 of 20 compared to the STAR; and the average of the IPE values from the exposure at high concentration (or integrated concentration) might be −5%, indicating that the devices exposed to the higher concentration are biased low compared to the STAR. The difference between the two values is 10% [i.e., 5% – (– 5%)]; therefore, the proportionality criterion is met in this example. 7.4 Temperature Radon measuring devices are typically calibrated at a temperature of approximately 21°C (70°F). If a temperature different from the calibration condition but within the range of temperatures generally found in indoor environments causes the radon measurement of the device to be substantially biased, then some manner of adjusting for this effect should be incorporated into the method. To ensure that test results adequately represent a device’s performance in a range of environments, a relatively tight control on humidity is required in the STAR u sed for testing the effects of temperature. 7.4.1 Criteria for Effect of Temperature Each individual device shall demonstrate an IPE within the range of 0 ± 25% when tested in a STAR f or a duration of time at least as long as the minimum recommended by the provider and in two conditions: (1) a relative humidity of 10 – 25% and temperature of 16 ± 3°C (60 ± 5°F), and (2) a relative humidity of 10 – 25% and temperature of 27 ± 3°C (80 ± 5°F). The COV for each set of five devices shall be less than or equal to 15%. 7.4.2 Test for Effect of Temperature Two sets of at least five devices are exposed in a STAR u nder the conditions specified in Subsection 7.4.1. The radon concentration should be greater than 370 Bq/m 3 (10 pCi/L) so that the measurement uncertainty due to the radon concentration itself is not large. If appropriate, the devices may be exposed to an integrated exposure of at least 370 Bq/m 3 (10 pCi/L) times the minimum time period recommended by the provider. The relative humidity should be kept as constant as practicable to a value in the range of 10 – 25%. As far as practicable, the radon concentration and relative humidity shall be the same during the two exposures. 7.5 Humidity Many radon-measuring devices are affected by the humidity in the surrounding air. If the measurements from a device are affected substantially over the range of relative humidity generally found in indoor environments, then some manner of adjusting for this effect should be incorporated into the method. 7.5.1 Criteria for the Effect of Humidity Each individual device shall demonstrate an IPE value within the range of 0 ± 25% when teste d in a STAR f or a duration of time at least as long as the minimum recommended by the provider and at a temperature in the range of 18 – 24°C (65 – 75°F) and values of relative humidity within the ranges of 15 – 25% and 70 – 80%. The COV value for each set of five devices shall be less than or equal to 15%. 7.5.2 Test for Effect of Humidity Two sets of at least five devices are expose d in a STAR under the conditions specified in Subsection 7.5.1. The radon concentration should be greater than 370 Bq/m 3 (10 pCi/L) so that the measurement uncertainty due to the radon concentration itself is not large. If appropriate, the devices may be exposed to an integrated exposure of at least 370 Bq/m 3 (10 pCi/L) times the minimum time period recommended by the provider. As far as practicable, the radon concentration and temperature shall be the same during the two exposures.