Smoke Particulate Monitors: 2006 Update
Real-Time Instruments
E-BAM—The E-BAM (the E stands for environmentally protected) monitor (figure 3) uses a three-part process to estimate the mass concentration of particulate. First, beta particles from a naturally occurring radioactive isotope are emitted through a clean filter tape and counted. Second, sampled air is passed through the exposed filter tape and particles are deposited. Finally, beta particles are passed through the tape again and recounted. The second count will be lower than the first, because beta particles will have been absorbed by the deposited particulate. The instrument uses an empirically derived algorithm to estimate the total mass of the deposited particulate. The estimated mass is divided by the volume of sampled air to calculate the average concentration in mass per unit volume. The exposed filter tape will advance automatically and begin a new collection after a userspecified time period or when the tape becomes clogged.
Figure 3—The E-BAM ambient particulate
monitor. This instrument collects particulate
on a filter tape and uses beta ray attenuation to
estimate particulate concentrations.
The E-BAM is a portable instrument that can operate using line (110 volts ac), battery, or solar power in the harsh environments typically found near a wildland fire without the need for an additional enclosure. It can be configured with EPA-approved PM10 and PM2.5 particle size separators (cutoff inlets) to remove particulate larger than 10 micrometers (PM10) or 2.5 micrometers (PM2.5) mean diameter, respectively. It uses pressure and ambient temperature sensors to recalculate flow at standard atmospheric conditions.
The E-BAM can be mounted on a tripod and configured to accept a variety of meteorological sensors for monitoring ambient windspeed and direction, relative humidity, and temperature. A six-channel data logger stores all the information. The range of measured concentration is 0 to 100 milligrams per cubic meter. The data logger can be programmed to report as often as every minute. Data can be downloaded at any time using an RS–232 serial port. A laptop computer or a modem can be configured to transmit the data using telephone lines, cell phone connections, or satellite telemetry.
The E-BAM is 16 inches high by 13½ inches wide by 8 inches deep. It weighs about 28 pounds without the PM10 or PM2.5 cutoff inlet. The cutoff inlets combined weigh an additional 7½ pounds and add 30 inches to the total instrument height. The power supply for 110-volt ac line power weighs 14 pounds. The ac pump (figure 4) is 10 by 16 by 18 inches and weighs 30 pounds. For more information, visit the Met One Instruments Inc. Web site at http://www.metone.com or call 541–471–7111.
Figure 4—The E-BAM monitor can be used with
an external ac electrical pump rather than the
internal dc pump, which is more likely to fail
after extended use.
E-Sampler—The E-Sampler (figure 5) is a forward-scattering nephelometer that uses light-scattering principles to estimate mass concentrations of airborne particulate. An internal visible laser diode is directed through the sample of air. Particulate in the sample scatters a portion of the light. The scattered light is collected at a forward angle and focused on a photodiode that converts the light to an electrical signal. The resulting signal strength is proportional to the amount of scattered light. An empirically derived algorithm converts the electrical signal to an estimated mass concentration.
Figure 5—The E-Sampler uses light scattering to
estimate particulate concentrations.
The E-Sampler is a small, lightweight instrument housed in an environmentally protected enclosure. It can estimate particulate concentrations as high as 100 milligrams per cubic meter. It can be configured with a cutoff inlet to measure total suspended particulate (TSP), PM10, PM2.5, or PM1. The E-Sampler can be mounted on a tripod and operated using line, solar, or battery power. A six-channel data logger accommodates other meteorological sensors that measure windspeed and direction, relative humidity, and ambient temperature. The sampler also has an inlet heater that can be programmed to operate when the inlet airflow's relative humidity reaches a particular level. Humidity can cause the instrument to overestimate particulate concentrations. The heater removes moisture from the air before it is sampled. However, the heater also may remove certain hygroscopic aerosols or convert them to a gas, reducing the estimated particulate concentration.
The E-Sampler is considered a dual technology instrument. Besides the realtime optical scattering measurement, the E-Sampler also incorporates a gravimetric filter system using the same 47-millimeter filter as the FRM sampler. While the gravimetric device does not provide results in real time, it can be used to develop correction algorithms to improve the accuracy of the real-time estimations.
The E-Sampler is compact—just 12 inches high by 10 inches wide by 5 inches deep. It weighs 13 pounds with the PM2.5 cutoff inlet, heater, and power supply.
For more information, visit the Met One Instruments Inc. Web site at http://www.metone.com or call 541–471–7111.
DUSTTRAK—The DUSTTRAK (figure 6) is a portable, battery-operated laser photometer that gives a real-time digital readout with a built-in data logger. The DUSTTRAK provides a real-time measurement based on 90-degree light scattering. A pump draws the sample air through an optics chamber where it is measured. The DUSTTRAK uses a system to provide a sheath of clean air that isolates the aerosol in the chamber, keeping the optics clean for improved reliability and reduced maintenance.
Figure 6—The DUSTTRAK is a lightweight
portable aerosol monitor.
The DUSTTRAK has a measurement range of 0.001 to 100 milligrams per cubic meter with a particle size range of 0.1 to 10 micrometers. Flow rate can be adjusted from 1.4 to 2.4 liters per minute. The monitor can be configured to measure TSP, PM10, PM2.5, or PM1. The internal data logger can store 31,000 data points (about 21 days of logging at one data point per minute). The DUSTTRAK can run on ac power or batteries. Four C-size alkaline batteries allow it to operate for 16 hours.
The DUSTTRAK is 8.7 inches high by 5.9 inches wide by 3.4 inches deep. It weighs 3.3 pounds with batteries. An environmental enclosure is available to protect the unit when it is used outdoors.
For more information on the DUSTTRAK, visit the TSI Inc. Web site at http://www.tsi.com or call 800–874–2811.
DataRAM 2000—The DataRAM 2000 (figure 7) is a compact, self-contained monitor that estimates mass concentration internally from the measured scattering of light. The monitor can measure particulate concentrations from 0.1 to 400,000 micrograms per cubic meter. The monitor continuously displays the current and time-weighted average mass concentration while logging up to 10,000 data points. Data can be downloaded from the monitor through an RS–232 serial data port. The DataRAM can be configured with either a PM2.5 or PM10 impactor head to prevent particles larger than 2.5 or 10 micrometers, respectively, from entering the optical chamber. For custom calibrations, or to analyze chemical composition, particulates can be collected on a 37-millimeter filter in the instrument's base.
Figure 7—The DataRAM 2000 is a single-wavelength,
light-scattering monitor.
Several of these
monitors are being used
by Forest Service air quality specialists, although
they are no
longer commercially
available.
An inline heater also may be installed for monitoring in humid conditions (the manufacturer suggests using the heater when the relative humidity is higher than 70 percent). The monitor's tubular heater is designed to heat the sampled air stream to evaporate liquid water from airborne particles or to eliminate fog droplets. The Data-RAM is powered by an internal rechargeable battery or by an external dc or ac power source. The DataRAM has a built-in, internal calibration device. Thermo Fisher Scientific Inc. no longer manufactures the DataRAM 2000.
DataRAM 4—The DataRAM 4 (figure 8) is an upgraded version of the DataRAM 2000. The DataRAM 4 uses light-scattering principles to estimate mass concentrations. The DataRAM 4 uses two light sources with different wavelengths (600 and 880 nanometers). In theory, this dual wavelength allows the DataRAM 4 to better estimate mass concentrations using an algorithm that incorporates scattering from each light source. The algorithm uses the mean particle diameter size computed from the light scattering to correct the mass concentration.
Figure 8—The DataRAM 4 is a dual-wavelength,
light-scattering monitor
that estimates particulate
concentrations.
Some of the new features of the DataRAM 4 include internal temperature and relative humidity sensors, the ability to autocorrect concentrations when measuring air that has high relative humidity, and the ability to measure mean particle diameter size. The monitor can measure particulate concentrations up to 400 milligrams per cubic meter and has a built-in data logger that can store as many as 50,000 data points. Like the E-Sampler, the DataRAM 4 has a built-in gravimetric filter system for custom calibrations, although its 37-millimeter membrane filter is smaller than the 47-millimeter filter used in the FRM sampler.
The DataRAM 4 monitor is 5.3 inches high by 7.3 inches wide by 13.6 inches deep and weighs 11.7 pounds.
For information on the DataRAM 4, visit the Thermo Fisher Scientific Inc. Web site at http://www.thermo.com or call 1–800–241–6898.
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