DEVELOPMENT OF A PORTABLE, LOW POWER PARTICLE MONITOR BASED UPON A SMOKE DETECTOR IONIZATION CELL
An inexpensive, and potentially portable particulate matter (PM) sensor was developed from an ionization chamber obtained from a household smoke detector. The devices performance was experimentally determined within a laboratory setting to assess the suitability of the technology for personal exposure monitoring. The sensor displayed a minimum limit of detection of 0.226 mg/m3 when 2001 measurements were averaged over the course of 2001 seconds, along with an average response time of 150 seconds. As the limit of detection is >10 times larger than PM mass loadings at most locations, the level of performance observed suggests the sensor will not allow routine PM exposure monitoring in most cities. However, the sensor may find use during high exposure periods or for workplace exposure monitoring. This was confirmed through monitoring PM levels during fry cooking within a dwelling. The sensor produced a large measureable response to the particulate matter created during cooking, indicating the sensor is suitable to monitor personal PM exposure at relatively high concentrations of particulate matter. In addition, relative humidity (water vapor) was observed to produce a strong negative interference (opposite response compared to particles) with the PM mass measurement. If the ionization cell is equipped with a filter to remove particles, the sensing principle could be employed as an inexpensive humidity sensor. Overall, a functioning, low-power particle monitor was successfully developed. Despite the sensor’s functionality, the dynamic range of the sensor is at particulate matter concentrations that are high in comparison to that of clean air. Therefore, without further improvement, the sensor’s only applications are in situations in which the concentration of particulate matter present is quite high.