Understanding Continuous Particulate Monitors

The U.S. Environmental Protection Agency (USEPA) defines particle pollution into two categories:

• PM₁₀ – Particulate matter with a diameter less than 10 microns,
• PM_2.5  – Particulate matter with a diameter less than 2.5 microns, also known as “fine particles.”

Traditional reference methods for measuring ambient PM concentrations are filter-based.  An unused filter is weighed in a laboratory prior to sampling, and then again after the sample period to determine the net mass of PM, which is used to calculate the average PM concentration in µg/m³.  Typically, filter-based samples are taken every three or six days, and the collection periods are 24-hours (from midnight to midnight), therefore the concentration measured is a 24-hour average.  There is an inherent delay associated with the filter handling and laboratory work, so data may be not be available for days or weeks. Newer equivalent methods allow for “continuous” PM monitoring, i.e., monitoring PM concentrations on a daily basis, and at a shorter interval, typically hourly.  Methods for continuous PM monitoring  include Beta-Attenuation-Monitors (BAMs) and Tapered Element Oscillating Microbalances (TEOMs). Air Sciences has deployed and operated continuous PM monitors for years with great success.  Wireless broadband or satellite communications have allowed us to monitor PM and meteorological data for our clients in near-real-time, and provide added value services for client’s such as:

• Creating diurnal profiles of PM concentrations to show concentration levels by the time of day,
• Creating “pollution roses” which combine hourly wind data and PM concentrations to graphically depict the origin of the PM as it relates to the air monitoring site,
• Sending automated email and text alerts to clients’ operational staff in the event of high monitored PM concentrations.  The alerts help clients to respond quickly and implement dust suppression methods, e.g., water trucks, process adjustments, etc.,
• Implementing visual alert systems, e.g., strobe lights, at clients’ facilities which show when high concentrations are monitored, which allows haul-truck or water-truck site personnel to perform dust mitigation or suspend operations,
• Assisting in event analysis during upwind and downwind monitoring compliance, aiding in hour-by-hour analysis of dust events as they complicate normal operational emissions.