The DataRAM4

The DataRAM4 particulate monitor is a compact, self-contained instrument that internally estimates the mass concentration of particulate in the air from the measured scattering of light. The DataRAM4 is a two-wavelength monitor. The stored data infor-mation includes average and maximum concentration values, particle size, internal temperature, and relative humidity with the time information as well as tag numbers. The instrument can estimate particulate concentrations from 0.1 to 400,000 micrograms per cubic meter of air. The instrument continuously displays the current and time-weighted average (TWA) mass concentration while logging up to 10,000 data points. Data can be transferred from the instrument to a laptop computer through the laptop's RS-232 serial port. A custom software package is provided with the DataRAM4 for communications to and from a personal computer.

The DataRAM can be configured with either a PM₁₀ or PM_2.5 instrument using the funnel-shaped DR-PM_10/2.5 inline impactor head (figure 1). To change the configuration, use the hex wrench provided to open the funnel and remove the three screws. A threaded stainless restrictor that is shipped with the instrument can be screwed inline inside the top of the funnel to convert the instrument to a 2.5-µm sampler. Most Forest Service DataRAMs will have this restrictor already in place. Use the 2.5-µm restrictor for monitoring wildland fire smoke.

An image showing both the inline impactor head and the PM2.5 nozzle.

Figure 1-Inline impactor head with the PM_2.5 nozzle installed.

For either the PM₁₀ or the PM_2.5 configuration, a 25-mm glass fiber filter sits on a plastic cassette filter holder inside the bot-tom of the funnel. In smoky conditions, check this filter every few days. If the filter has dark brown or black spots, discard it and replace it with one of the new ones provided. When the DataRAM is running in relatively clean air, the filter should be replaced about every 30 days.

In the bottom of the instrument, a large screw cap protects another filter. Two types of filters can be inserted-one is a metal cartridge HEPA filter and the other is a 37-mm filter in a plastic cartridge. The HEPA filter should be used for routine smoke sampling. The 37-mm filter is intended to catch particles to be analyzed later. Although the 37-mm filter and cartridge are shipped with the DataRAM, do not use it unless you have consulted with an air quality specialist.

An inline heater should be installed for conditions above 70-percent relative humidity. The inline heater requires 120-volt line power. Humidity of 70 percent and above may occur at any time in the early morning, even during low-humidity days.

The tubular heater is designed 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 Missoula Technology and Development Center (MTDC) recommends having 120-volt line power available for the DataRAM and inline heater even though the DataRAM can be operated on a battery for about 20 hours.

The DataRAM is not approved by the U. S. Environmental Protection Agency (EPA) as a reference (or equivalent) fine-particle monitoring sampler. The DataRAM provides general trends of smoke particulate concentration. These data can enable the user to verify whether the impacts of smoke partic-ulate are increasing or decreasing. The estimated DataRAM particulate concentration can be adjusted internally using a correction factor. For wildland fire smoke PM_2.5, the correction factor is 0.48 for a flow of 2.0 liters per minute. To check and adjust these parameters, see 'Setting Parameters'.

The center published Real-Time Smoke Particulate Sampling: Fire Storm 2000 (0125-2832-MTDC) which explains EPA air-quality standards and how the DataRAM4 correction factor of 0.48 was determined.

E-mail: wo_mtdc_webmaster@fs.fed.us

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