Performance of Home Smoke Alarms - National Institute of ...

lags the MIC current due to the time difference between the aerosol transport through the tubingand chamber filling, but the steady voltage value is proportional to the MIC current. Thereported ion chamber values in the nuisance tests below differ by a constant value due todiffering amplifier gains.In the nuisance tests, the copper tubes used to transport the air sample to the devices were 2.5 mlong. Chamber #1 was located in the living room area, while chamber #2 was located in thekitchen area next to the other aerosol sampling points (figure 140).6.2.2 Temperature and HumidityA type-K 0.5 mm stainless steel sheathed thermocouple monitored the ceiling air temperature. Itwas placed at the aerosol sampling location, 3 cm below the ceiling.Figure 144 is a picture showing thethermocouple placement along with theCPC, Dustrak, and ion chamber 2 samplinglines.An Oakton 35612 series thermohygrometerprobe was used to monitor the relativehumidity throughout the experiments. Theprobe was positioned 2.0 m off the floor atthe position indicated by “RH” in figure141. The stated measurement uncertaintyfor this device is 2.5 % of the reading.ThermocoupleCeilingRidgeCPCAndDustrakIonChamber6.2.3 Flow VelocityFigure 144. Thermocouple and sampling lineThree CATI sonic anemometers (AppliedplacementTechnologies Inc.) were used to record the two-component air velocities perpendicular to thesloped ceiling at a depth of 5 cm. Their locations are shown in figure 141 and identified asanemometer A1, A2, and A3. The component velocity orientation is also shown.These devices use piezoelectric crystals to form ultrasonic transducers that can send and receiveultrasonic pulses. The forward and backward travel time of these pulses are used to compute thecomponent velocity between two opposing transducers. The anemometers record the meanvelocity over a 15 cm sonic path length (which equals the distance separating opposingtransducers) at a frequency of up to 10 Hz. The measurement resolution is 1 cm/s with a stateduncertainty of 1 cm/s.153