NHDES has monitored particulate matter since 1967. Over the years, monitoring efforts have focused on different sized particles and incorporated different methods of measurement. NHDES currently monitors PM10 at three locations and PM2.5 at seven locations throughout the state (see map below). Please visit Air Quality Monitoring and Data for more about air quality monitoring in New Hampshire.
Monitoring by Particle Size
Early particulate matter monitoring from 1967 to 1987 focused on total suspended particles (TSP, all particle sizes). As research revealed that the worst health effects result from the smallest particles, monitoring efforts shifted from TSP to PM10 and PM2.5. NHDES established an extensive monitoring network for PM2.5 beginning in 1998.
Initially, the only method available for measuring particles was a filter-based method. A technician set up a filter, allowed it to collect particles for 24 hours, picked up the filter when sampling was complete, and shipped it to a laboratory for analysis. This provided a day’s average
concentration, but the results were not available from the lab for weeks to months after the sampling day. Moreover, because of the time needed to set up and remove the filters, NHDES would only run the filters once every few days.
Advances in technology have created significant changes in particulate matter monitoring. Today, NHDES uses the filter method along with new instrumentation capable of measuring particulate matter on an hourly basis. The newer method provides hourly measurements of particle concentration every day of the year. Automated computer systems continuously transmit these data to NHDES computers and websites for real-time viewing and analyses. NHDES uses an instrument called a Beta Attenuation Monitor (BAM) to measure hourly PM2.5 concentration at five sites: Keene, Londonderry, Portsmouth, Lebanon and the summit of Pack Monadnock in Peterborough.