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Purpose: Measure the quantity of particulates present in the air by collecting the particulates on a filter. The mass of particles collected on the filter, combined with the amount of air passed through the filter, will be used to determine the concentration of particulates in the air during the sampling period.

I. Filter Analysis: All filter analyses will be conducted in a laboratory room controlled for temperature, humidity, and air flow currents. The balance used for the analysis will be capable of measuring to one (1) microgram. The balance will be calibrated before and after the analysis of each set of filters (pre-sampling and post-sampling) described below.

A. Inspection: All filters will be visually inspected for defects before initial weighing. Any filter found defective will be rejected. Example defects include, but are not limited to, the following:

  1. Pinholes
  2. Loose Material
  3. Discoloration
  4. Irregular Surfaces

B. Pre-sampling Preparation: Unexposed filters will be placed in a desiccator at least 24 hours prior to sampling. The filters will be removed from the desiccator no more than one (1) day prior to use in the field. When outside the desiccator, the filters will be stored in a protective cassette. Each filter will have a unique ID number consisting of the sampling day and inlet used. The ID number will be placed on the filter’s protective cassette.

  1. Filter Weighing: The filters pre-sampling weight will be measured on a microscale balance no more than one (1) day prior to use in the field. The following procedure will be used:

    1. Remove filter from the protective cassette.
    2. Using teflon coated forceps, pass the filter over a deionizing strip.
    3. Weigh filter, recording both the weight and the filter ID.

  2. Installation in Sampler Inlet: The following procedures will be followed for installing the filter in the sampler inlet. The sampler’s operating manual should be consulted for further details

    1. Install pre-weighed filter onto the filter support grid.
    2. Replace locking ring, being sure all cut notches are aligned (Note that improper alignment will result in damage to the filter).
    3. Connect the filter holder unit with the preseparator adapter (units should fit tightly but not over torqued).
    4. Place a new, clean plastic bag securely over the entire filter assembly, and place in the corresponding battery case for transport to the field.

  3. Controls: Two filters will be set aside as controls for each sampling day.
    1. Lab Control the lab control filter will be pre-weighed then placed back in the dessicator. This control will measure precision of the laboratory technique.
    2. Field Control the field control will be pre-weighed, placed into a sampler inlet, and transported to the field. This control will determine any potential contamination during transport and handling in the field.

C. Post-sampling Analysis: Exposed filters will be placed in a desiccator no more than 24 hours after collection in the field. When outside the desiccator, the filters will be stored in a protective cassette. Each filter will have a unique ID number consisting of the sampling day and inlet used. The ID number will be placed on the filter’s protective cassette.

  1. Filter Weighing: The filters post-sampling weight will be measured on the same microscale balance as used for the pre-sampling measurements. The following procedure will be used:

    1. Remove filter from the protective cassette.
    2. Using teflon coated forceps, pass the filter over a deionizing strip.
    3. Weigh filter, recording both the weight and the filter ID.

  2. Controls: The two control filters corresponding to the post-sampling filters’ dates will be analyzed by the same procedures described above.

D. Gravimetric Analysis (Cahn Model C-33 balance): It is suggested that the balance will be located in a room controlled for temperature, humidity, and air flow currents. If this is not possible, weighing error only rises slightly. Calibration with a NIST-traceable 200 mg weight will occur prior to filter analysis, and after every 20 samples analyzed. The calibration weight will be stored in a separate container in the temperature controlled lab, and dedicated teflon coated forceps will be used for handling to avoid contamination. If calibration error is greater than 2%, the balance will be adjusted and all previously analyzed samples will be re-weighed. The balance will also be equipped with static de-ionizing units, one centered in the balance, and one mounted near the balance, to eliminate sample artifacts from static charges. The balance will be turned on and allowed to warm up for a minimum of 30 minutes before use to attain stability.

II. Sample Storage: All PM samples will be stored in a dessicator to reduce the presence of water vapor on the filter, affecting it's weight from humidity effects. The dessicators will be stored in a temperature controlled room to reduce filter artifacts from volatilization of particulate constituents. After analysis, each filter will be placed in a separate cassette and stored for a period no less than six (6) months in the temperature controlled room.

III Sampling Procedure: The following procedures will be followed in the field to collect exposed filters and install unexposed filters.

  1. Exposed Filter Collection

    1. Remove sampler from hanging bracket. The sampler should be lowered vertically to avoid dislodging or damaging the sampler inlet.
    2. Place the sampler in a clean, flat place and remove the bail handle.
    3. Lift the pump and timer assembly out of the sampler housing and record the flow totalizer value. Also note if the low-battery indicator light is lit (if so, the reset button must be pressed).
    4. Turn on the sampler and record the flow rate on the rotameter. Allow the sampler to run for a minimum of 30 seconds before recording the flow rate (note that the sampler should be in a vertical position while reading the flow rate). Verify the flowrate reading with a NIST-traceable bubble flowmeter.
    5. Remove the exposed filter assembly and place in a clean plastic bag.

  2. New Filter Installation

    1. Remove the plastic bag from the clean filter assembly and connect to the sampler.
    2. Replace the used battery with a charged battery.
    3. Record both the filter ID and the battery ID.
    4. Turn on the sampler and record the flow rate (after a minimum of 30 seconds). Verify the flowrate reading with a NIST-traceable bubble flowmeter. After recording the flow rate, check for leaks by covering the inlet. If the sampler does not shut off in a minute, leaks are present, and the sampler inlet must be replaced. If the sampler shuts off, press the reset button, and turn off the sampler using the keypad.
    5. Set the sampler timer to operate during the sampling period, and set the keypad to Auto (see operating manual for details).
    6. Connect the bail assembly, and replace the monitor on the bracket.
    7. Record the time and date the filter and battery exchange occurred.

IV. Sampler Maintenance

    A. Impactor: After every seventh sample, the impaction stage will be cleaned and regreased in a well ventilated area using the following procedures.

    1. Remove the raincap and detach the impactor section through the top of the tube by pushing with the thumb through the bottom.
    2. Rinse the impactor from top to bottom with hexane using a squeeze bottle.
    3. Let impactor air dry.
    4. Place three (3) drops of an Apiezon M/hexane mixture (see operating manual for details) on the impaction stage, allowing the drops to saturate the stage.
    5. Let the mixture dry, leaving a thin film of grease on the stage.
    6. Inspect the O-rings and clean the entire assembly. Replace any worn or unfit parts.

    B. Battery: The battery packs will be exchanged and recharged after each sampling day. Each battery will be recharged until the charging indicator light turns off. The AA batteries for the timers will be replaced every six (6) months.

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