Envirotech APM 460 series samplers have a size cut off closely resembling the Thoracic particle retention curve of the human respiratory tract. This size distribution (shown below) conforms to the popular PM 10 convention and has a D50 at 10 microns.

The filter holder of the APM 460 series samplers accept any filter paper of size 8" x 10". For common use Whatman GF/A grade Glass Fiber filters are used. If you wish to analyze the chemical composition of the PM 10 particulates Whatman EPM 2000 is recommended. These filter papers are usually available with your local scientific goods dealer, else you can order them from Envirotech..

If you are doing a gravimetric determination of PM 10 any moisture trapped in the filter or adsorbed on the particles can affect your results. So it is a good idea to dry or equilibrate your filters before and after use. 

EPA recommends that you place the filters in a controlled Humidity Chamber (RH < 25%) at 25 degrees Celsius for at least 16 hours to equilibrate the filters. A large desiccator is often used. Remember to periodically recharge the desiccant in your desiccator. 

As the sample progresses fine particles (PM 10 fraction) of dust get deposited in the pores of the filter paper. This increases the resistance offered by the filter to the passage of air. In APM 460 RDS the Blower causing air flow is operating at a fixed RPM so increased pressure drop across the filter causes a drop in flow rate through the system. 

The APM 460DX model RDS incorporates an automatic flow controller which constantly monitors the flow rate through the filter paper. Initially when the filter paper is relatively clean part of the Blower capacity is bypassed through a valve. As the filter gets choked and offers greater resistance the flow controller dynamically adjusts the bypass air flow to allow a greater suction capacity of the Blower to operate through the filter. As such the flow controller maintains a constant air sampling rate through the filter.

The location of your Air Quality Monitoring station is determined by your objective. If you are monitoring air quality for compliance testing consult your Pollution Control Board or regulatory agency for location of the station. If you are concerned about the health of a specific community locate the sampler in their neighborhood.

A sampler located on the roadside is bound to be affected by road lifted dust as it is located in the immediate vicinity of this source. However, much of this dust is likely to settle fairly rapidly. In general, locate the sampler on the roadside ONLY if you are studying traffic related air pollution or the impact on pedestrians, shoppers etc. who are likely to be exposed to air quality on the road. For community air quality studies particularly in the Indian dry and dusty environment it is better to locate the sampler on a roof-top say 3 to 6 meters above ground and somewhat away from a busy road.

Respirable Dust Samplers made by Envirotech use a field proven orifice plate based flow metering system that is designed to give you trouble-free operation for several years. However, ISO requirements stipulate that measuring equipment should be re-calibrated every year. 

Yes! re-calibration in the field can be performed by using the APM 421 Top Loading Calibrator. Envirotech Center for R&D also provides a calibration facility at a nominal cost.. 

The absorbing reagent used is Sodium Tetra Chloro Mercurate. Consult BIS 5182 part for details on the test method for determination of SO2 using the West & Gake method.