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• Overview of Sampling Process

  1. Select the employees to be monitored and discuss with them the purpose of sampling, how the equipment will be placed, and when and where the sampling equipment will be put on and removed
• Overview of Sampling Process

  2. Place the calibrated sampling equipment on the employee so that it does not interfere with the employee's work performance or safety
• breathing zone (i.e., within a radius of approximately six to nine inches)
• The collection device inlet should be oriented in a downward vertical position to avoid gross contamination from airborne debris falling into the collection device
• When sampling using a cyclone, position the inlet (vortex finder) so that it faces away from the employee
• For an employee wearing a welding helmet which is not a respirator, the collection device shall be placed under the helmet
• Overview of Sampling Process

  3. Open the inlet to the collection device as appropriate to the sampling method and turn on the air sampling pump
• Overview of Sampling Process

  4. Document the sampling pump start time and other required information. For diffusive samplers be sure to record the temperature and any other parameter as required.
• Overview of Sampling Process

  5. Strive to sample for at least the minimum air volume or sampling time prescribed in the sampling method
• In the case of filters, overloading = the presence of loose material in the filter cassette, darkening of the filter and/or by a reduction in the sampling pump flow rate.

  For sorbent media, overloading occurs when the ability of the sampling medium to effectively collect the analyte is compromised.
• In general, overloading can be avoided by replacing the collection medium several times during the work shift (once the minimum sample volumes are achieved)
• Overview of Sampling Process

  6. Periodically monitor the employee throughout the workday to ensure that sample integrity is maintained. Frequent pump checks may be necessary, especially when heavy filter loading is possible
• Overview of Sampling Process

  7. Before removing the pump at the end of the sampling period, check the pump flow readout (e.g., digital readout or built-in rotameter) to be sure it is still running
• Overview of Sampling Process

  8. Turn off the pump and document the stop time
• Overview of Sampling Process

  9. Remove the sample media from the connecting tubing and close both the inlet and the outlet of the collection device as appropriate, e.g. using caps or plugs
• Overview of Sampling Process

  10. Complete chain of custody form and submit to analytical lab in accordance with specified transport requirements (as per the NIOSH/OSHA method)
• When a toxic metal such as lead is present in a workplace as both dust and fume, it may be necessary to sample separately for the dust and the fume
• Will need two pumps if sampling for:  A gas/vapour and particulate OR  Two different particulates
• Not very practical to wear more than two pumps
• Purpose of collecting multiple samples from a worker:  To understand exposure profile for certain tasks/procedures  For STEL and TWA compliance monitoring  To prevent oversaturation of media
• Purpose of collecting multiple samples from a worker over different days

  • To understand differences between days/seasons
  • Get a more accurate idea of level of compliance
• NIOSH suggests a minimum of 6 samples from every SEG identified
• If you have two SEGs, you will need a minimum of 6 workers from SEG #1 and 6 workers from SEG#2
• Calibration curve - Defines the relationship between the instrument output and the contaminant level in the sample
• At a minimum, this curve requires the plotting of the zero concentration and several known concentrations to complete the curve
• Calibration - The set of operations that establish, under specified conditions, the relationship between values indicated by a measuring instrument/system and the corresponding values of the material to be measured
• Sensitivity

  • A measure of the smallest value of any parameter that is to be monitored that can be unequivocally measured by the system of interest
  • Is a function of the inherent noise (background) that is present in any analytical system
  • Also referred to as “detection limit”
• Specificity

  • The capability of any analytical system to provide accurate responses to a desired analyte even in the presence of factors that might potentially interfere with the overall analytical process
  • E.g. metabolites and impurities
  • Also known as “selectivity”
• Interferences - Contaminants that influence the outcome of the analytical results, either high or low
• Precision

  • a.k.a repeatability or reproducibility
  • Closeness of agreement between repeated measures
  • The ability of an analytical system to deliver consistently identical results to specific analytical challenges independent of any other factors
  • i.e. provides the same result when challenged with a known level of the material for which the system was designed to monitor Examples: different operators, different times of day
• Accuracy

  • Degree of agreement between a measured value and the true concentration (reference value)
  • Ability of an instrument to determine the true concentration of the environment sampled
• Instrument bias - Refers to the instrument's systematic deviations from accuracy

  • The larger the deviations the larger the bias value
  • Affects accuracy; not precision
• You want the analytical method to be

  • Sensitive
  • Specific
  • Precise
  • Accurate
• NIOSH classifies the methods according to level of validation

  • Full
  • Partial
  • Unrated
• Validation = evaluated for precision, accuracy, recovery, stability, and collection efficiency
• OSHA - Includes both validated and experimental “stop-gap” (partially validated) methods
• Choice of method depends on:

  1. Available instrumentation
  2. Sensitivity required
  3. Interferences present
  4. Availability of sampling media
  5. Sampling flow rate
  6. Sampling time (duration)
• The primary purpose of the American Industrial Hygiene Association (AIHA) Laboratory Quality Assurance Programs (LQAP) is to establish and maintain the highest possible standards of performance for laboratories analyzing samples
• Accredited labs operate a quality system that meets the requirements of the International Organization for Standardization (ISO) Standard ISO/IEC 17025
• Accreditation requires an evaluation of:

  1. laboratory personnel qualifications
  2. laboratory facilities
  3. quality control and equipment
  4. laboratory record keeping; and
  5. methods of analyses