Document NebyqzzaamkvVeDnGYbO191Xw

Jr* 1 -+ * "Hu Interoffice Communication To F. Scott From D COX * Oat. 2-1W5 subject Accuaracy of Honeywell Fixed Point Monitors Unit located In VII Dryer Building p A standard gas sample was run for 20 hrs and the variation due to the Instrument measured. The standard deviation , g- , for the 0-50 ppm Range was found to be 0.45 ppm. At 95% confidence level a reading on the 0-50 ppm scale will be within + 0.98 ppm of the true value. This is an unacceptable uncertainty at 0.5 to 4.0 ppm level. Discussion i- A bottle of VCM <in air, 20.6 ppm Average, was attached to the analyzer in the drier building and a total of 1152 individual analysis were made. The standard deviation was derived by taking every 25th analysis. There was a 6-7 hr. cycle as was seen in the lab unit. In addition after about 12 hrs. a gradual baseline drift began to occur. The test was not run long enough to determine if this was evidence of a longer cycle drift or not. However, for-all readings above 4 ppm the legal requirements of +25% are reached but levels below 4 ppm cannot be used without further testing at the'lower level. ( recommend this unit be retested. . L VAB.0001039714 *