"PERSONAL SAMPLING FOR AIR CONTAMINANTS
Introduction
How to Order Sampling Media
General Monitoring Requirements and Guidelines
Field Blanks
Total Dust
Respirable Dust
Crystalline Silica
Metals Sampling
Asbestos
Organic Vapors and Gases
Sampling and Analytical Error (SAE)
Soils Analysis in Support of the Excavation Standard
Custom Services Provided by SLTC
Bibliography
Appendix II: 1-1
Appendix II: 1-2
Appendix II: 1-3
Appendix II: 1-4. Partial List of Substances for Gravimetric Determination
Appendix II: 1-5. Cyclone Assembly and Cleaning Instructions
Appendix II: 1-6. Chain of Custody
Appendix II: 1-7. How to Apply Form OSHA-21 to Charcoal Tubes and Filter Cassettes
Appendix II: 1-8. Completed Air Sampling Worksheet Form OSHA-91A
Appendix II: 1-9. Completed Soil Sampling Worksheet on a Form OSHA-91A
INTRODUCTION
This chapter provides basic information related to sampling air contaminants. These instructions are essential for acquiring documented and valid exposure data that will be defensible in the event of contested citations.
This chapter is one of a number of references for sampling air contaminants. Other reference resources that should be routinely consulted are OSHA's Chemical Sampling Information (CSI) file and the OSHA Field Inspection Reference Manual (FIRM). The FIRM identifies CSHO responsibilities associated with the majority of their inspection duties. OSHA and National Institute for Occupational Safety and Health (NIOSH) validated sampling and analytical methods should be reviewed, and when necessary, the Salt Lake Technical Center (SLTC) analytical staff should be consulted. It is extremely important that SLTC-approved sampling procedures or procedures described in the CSI that have been approved by the SLTC be used.
OSHA sampling and analytical methods were developed to provide OSHA with validated methods to monitor workplace exposure to a wide variety of chemical substances. These methods were validated with the use of evaluation guidelines that are published on OSHA's website. The guidelines define sampling and analytical parameters, specify required laboratory tests, statistical calculations, criteria for acceptance, and provide a detailed outline for the written reports. The overall goal of these guidelines is to provide OSHA with sampling and analytical methods that can be clearly defended with evaluation data. These sampling and analytical methods were designed and tested for internal use by OSHA personnel. The use of nonstandard sampling methods may require resampling with a SLTC-approved sampling procedure. The SLTC is aware that unique sampling situations will arise during some inspections and close coordination with the laboratory will provide the best analytical service.
Sampling strategies should be planned for a meaningful evaluation of air contaminants and prudent use of limited resources. Screening techniques and devices, such as detector tubes and direct-reading meters may, provide valuable information when their use and their detection limits are appropriate (see Section II: Chapter 3 Technical Equipment: On-Site Measurements). Knowledge of sampling requirements such as sampling media, recommended air volumes, and sample storage precautions are essential in planning proper sampling strategies.
Bulk samples are sometimes necessary to support analyses of air samples and to document the source of air contaminants. They are required for certain analyses such as explosibility and flash point testing. They are sometimes used in Hazard Communication inspections (i.e., Material Safety Data Sheet (MSDS) compliance). Consult OSHA's Chemical Sampling Information file to determine when bulk samples are appropriate. Bulk samples often require special shipping and handling.
Ensure that appropriate sample shipping and handling requirements are followed (see Chapter 4, Sample Shipping and Handling) and that the mode of shipment is appropriate for the requested analytical service. For example, "Rush Analysis" requires sample shipment with overnight delivery. If samples are for "Rush Analysis," then concurrence by the Area Director is required. Follow all chain-of-custody protocols and make certain that samples are properly documented on the Air Sampling Worksheet Form OSHA-91A (see Figures II: 1-24 and II:1-25 for a completed Form OSHA-91A) and properly sealed with Form OSHA-21 as shown in Appendix II: 1-6. Apply the Form OSHA-21 in such a manner that the chain-of-custody information is not obstructed.
HOW TO ORDER SAMPLING MEDIA
OSHA personnel can order sampling media from the SLTC using the order form located on the OSHA limited access Intranet under CSHO Resources. Charcoal tubes, asbestos pre-assembled filters and cassettes, Form OSHA-21 seals, cyclones, and mixed cellulose ester filters (MCEF) should be ordered from the Cincinnati Technical Center (CTC).
The SLTC provides pre-weighed filter/cassette units for gravimetric sampling and analysis to OSHA personnel. The filters are weighed at the SLTC and shipped to the field assembled in special cassettes to be used for sampling. The cassette/filter units are returned to the SLTC after sampling for gravimetric determinations and for other analyses. Refer to OSHA's Chemical Sampling Information file or to Appendix II: 1-4 of this document for a list of analytes in this category.
GENERAL MONITORING REQUIREMENTS AND GUIDELINES
A. Documentation
It is essential that accurate and complete sampling pump calibration records and field sampling notes be recorded on Form OSHA-91A (Air Sampling Worksheet), which also serves as a sample submission document for samples requiring analysis by the SLTC. Be sure to use designated sample media to perform pre/post calibration. Do not use the same media for calibration and field sampling. SLTC chemists sometimes use sampling pump calibration data to verify air sample volumes. Detailed line-by-line instructions for completing this document are given in Chapter XXI (Air Sampling Worksheet, Form OSHA-91A) of OSHA Instruction IRT 01-00-007 (previously ADM 1-1.31) (The IMIS Enforcement Data Processing Manual for use with the NCR Computer System). Ensure that handwritten information is printed legibly. Accurate and consistent spelling of the inspected establishment name will facilitate future database searches. A completed Form OSHA-91A (Air Sampling Worksheet) is shown in Figure II: 1-24 and Figure II: 1-25 of Appendix II 1-8 in this document.
Diffusive samplers are convenient air sampling devices that sample gases and vapors and do not require the use of a sampling pump. OSHA diffusive sampling methodology exists for only a few chemicals. Refer to the Chemical Sampling Information file and the ORGANIC VAPORS AND GASES section of this document for diffusive sampling applications and guidance. When using diffusive samplers, record the sampling site temperature and pressure on the Form OSHA-91A (Air Sampling Worksheet). The barometric pressure for the time period sampled can sometimes be obtained by calling the local weather station or airport or by accessing National Oceanic and Atmospheric Administration information on the Internet. If air pressures are obtained by these means, it is necessary to obtain the unadjusted barometric pressure (station pressure) for compliance applications.
Take photographs (as appropriate) and detailed notes concerning visible airborne contaminants, work practices, potential interferences, workplace movements, and other conditions to assist in determining appropriate engineering controls. Ventilation and/or smoke tube measurements may also be helpful. Be certain to observe if the employees wore the sampling equipment properly. This is sometimes an important issue in litigation. Refer to the FIRM for a more thorough discussion of inspection documentation procedures.
B. Sampling Protocol
Determine as soon as possible after the start of the inspection whether full-shift air contaminant sampling is required by using the information collected during the walkaround (including any screening samples) and from the pre-inspection review. To eliminate errors associated with fluctuations in exposure, conduct representative full-shift sampling for air contaminants when determining compliance with an 8-hour Time-Weighted Average (TWA) Permissible Exposure Limit (PEL). Full-shift sampling is defined as a minimum of the total time of the shift less 1 hour (e.g., 7 hours of an 8-hour work shift or 9 hours of a 10-hour work shift). Make every attempt to sample as much of the work shift as possible and include segments of greatest exposure during the sampling periods. However, no more than 8 hours of sample can be used in the 8-hour TWA-PEL calculation (refer to discussion on extended work shifts below). A representative exposure sample period may be less than seven hours; however, the final analytical result and associated calculation could still result in non–compliance when averaged over 8 hours.
Extended Work Shifts: Compliance officers can choose one of two approaches for employees who work extended work shifts beyond 8 hours. The choice taken will depend on the nature of the hazardous chemical and the work activity being performed.
The first approach is to sample what the compliance officer believes to be the worst continuous 8-hour work period of the entire extended work shift.
The second approach is to collect multiple samples over the entire work shift. Sampling is done so that multiple personal samples are collected during the first 8-hour work period and additional samples are collected for the extended work shift. Unless a compliance officer is dealing with lead, the employee’s exposure in this approach is calculated based upon the worst 8-hours of exposure during the entire work shift. Using this method, the worst 8–hours do not have to be contiguous. Example: for a 10-hour work shift, following established sampling protocol as per the CSI file, ten 1-hour samples or five 2-hour samples could be taken and the eight highest 1-hour samples or the four highest 2-hr samples could be used to calculate the employee's 8-hour TWA, which would be compared to the 8-hour TWA-PEL.
At the time of this revision, the lead standards for construction and general industry are the only standards that require PEL adjustments with respect to extended work shifts.
To reduce their level of exposure, the occupational exposure to the Cotton Dust standard, 29 CFR 1910.1043, has a requirement to adjust extended work shifts when employees are required to wear respirators for a portion of the work shift.
The following guidance provides an overview of the sampling process:
Select the employees to be monitored and discuss the purpose of sampling. Inform the employees of when and where the sampling equipment will be removed. Stress the importance of not removing or tampering with the sampling equipment. Instruct the employees to notify their supervisor or the CSHO if the sampler requires temporary removal.
When assembling air sampling filter cassettes, it is crucial to verify that the two halves of the cassette are firmly and completely seated against each other to prevent sample material from bypassing the filter. Do not mix brands of cassette components. A hand press can be used to ensure a good seal between the filter and the cassette halves. Examine the assembled cassette to make certain that the joints fit together securely. Use shrink tape around the cassette to cover joints.
Place the calibrated sampling equipment on the employee so that it does not interfere with work performance or safety of the employee. Attach the collection device (filter cassette, charcoal tube, etc.) to the shirt collar or as close as practical to the nose and mouth of the employee's breathing zone (i.e., in a hemisphere forward of the shoulders within a radius of approximately nine inches). The inlet should be oriented in a downward vertical position to avoid gross contamination from airborne debris. The length of the tubing connecting the collection device to the sampling pump should not be excessive and it should be secured to the employee. This will help to prevent the tubing from being snagged or from interfering with the employee's job function. The inlet (vortex finder) for a cyclone should be oriented so that it faces away from the employee. The practice of placing the sampling devices inside personal protective equipment (PPE) applies only to PPE that is not intended to provide respiratory protection such as welding helmets. This sampling is performed to determine if respiratory protection is needed. Sampling outside of the PPE is used to determine if the correct assigned protection factor is being applied. If the PPE has supplied air, such as a welding hood or an abrasive blasting hood, then the sample is placed outside the PPE.
Turn on the sampling pump and record the start time (time on) on the Form OSHA-91A (Air Sampling Worksheet). After starting, observe the pump operation for a short time to make sure that it is operating correctly.
Record the information required on the Form OSHA-91A, including the sampling site temperature and pressure for diffusive samplers. Be sure to print legibly on all forms.
To ensure that a potential exposure level is effectively measured with respect to a specific regulatory standard, strive to sample for at least the minimum sampling time/air volume prescribed in the OSHA Chemical Sampling Information file when a minimum time is listed. Exceptions to this guideline would be when overloading of the sampling medium is anticipated or observed during sampling. Overloading is characterized by saturation of the sampling medium. In the case of filters, overloading may be evidenced by the presence of loose material in the filter cassette and/or by a reduction in the sampling pump flow rate. For adsorbent media, overloading occurs when the ability of the sampling medium to effectively collect the analyte is compromised. In practice, overloading is difficult to detect and CSHOs should use their observations, experience, and professional judgment to avoid this adverse sampling situation.
Periodically monitor the employee throughout the workday to ensure that sample integrity is maintained and cyclical activities and work practices are identified. Do not enter areas where sampling is being conducted without the appropriate personal protective equipment. Frequent pump checks may be necessary, especially when heavy filter loading is possible. For air sampling filters, verify symmetrical deposition of particulate on the filter and the absence of unexpected large particles, or any evidence of tampering with the sample or pump. Ensure that the sampler remains properly assembled and that the hose does not become pinched or detached from the sampling device or from the pump. Record any relevant observations. Turn off or remove sampling pumps immediately prior to an employee leaving a potentially contaminated area (such as when he/she goes to lunch or on a break in a clean area). If these areas also appear contaminated and are considered part of the workplace, continue sampling and assess the need for surface contamination measurements (see also Section II, Chapter 2, Occupational Skin Exposure, Biological Monitoring and Surface Contamination (Wipe) Sampling). If the pump is turned on and off during the course of the day and if the sampling media is not changed, record subsequent times (time on/time off) on the Form OSHA-91A (Air Sampling Worksheet).
Before removing the pump at the end of the sampling period and if the pump has a rotameter, check the pump to ensure that the rotameter ball is still at the calibrated mark. If the ball is no longer at the mark, record the pump rotameter reading.
Turn off the pump and record the stop time (time off) on the Form OSHA-91A (Air Sampling Worksheet).
Remove the collection device from the pump, cap or otherwise close the sampler, and seal it with a Form OSHA-21 as soon as possible. The seal should be attached across the sample inlet and outlet so that evidence of any tampering is visible (see Figures II:1-19, II:1-22, and II:1-23.) Figures II:1-20 and II:1-21 are illustrations of incorrect application of Form OSHA-21 seals. Press the seal onto the cassette to ensure that the adhesive adheres firmly to the sampling media surface. Samples with seals that can be removed without obvious evidence of tampering will be identified as "Proper seals not in place" in SLTC reports of analytical results.
Indicate on the Form OSHA-91A if analytical results are to be reported as TWA results calculated using the actual time sampled or if they are to be reported as "8-hour TWA" results calculated using zero exposure for non-sampled time portions of the 8-hour period. OSHA TWA-PELs are defined as 8-hour TWA exposures. Record results of post-calibration for all pumps used on the OSHA-91A.
Prepare the samples for transport to the SLTC for analysis. Submit bulk samples and air samples separately to avoid cross-contamination. If any submitted materials could be considered hazardous, consult and follow appropriate shipping regulations to assure safe handling during shipment (See Section II, Chapter 4 or contact the SLTC for instructions). Pack the samples securely in a box or other sturdy container to avoid any rattle or shock damage. For asbestos samples, do not use expanded polystyrene packing (Styrofoam™) or other static producing packaging material. Place samples in a plastic bag so that they do not move freely. Use bubble sheeting or other material as packing. Put identifying paperwork in every package. Do not send samples in unpadded envelopes. Make sure that you include a copy of Form OSHA-91A (Air Sampling Worksheet) with the samples.
FIELD BLANKS
Blank samples are required for each requested analysis, and for each lot number of sampling media. Prepare field blanks during the sampling period for each type of sample collected. One field blank will usually suffice for up to 20 samples for any given analysis/sampling period except for asbestos, which requires a minimum of two field blanks, even for a single asbestos sample. Field blanks (e.g., charcoal tubes, filters) should be opened in the workplace but not used to take samples. They should be handled, stored, and shipped in the same manner as other sampling media used in sampling air contaminants, with the exception that no air is drawn through them. Diffusive samplers should be briefly opened in the field in an area on-site where no contamination is expected and then immediately resealed with manufacturer's materials. Diffusive samplers begin to sample as soon as they are opened and continue to sample until they are sealed. Follow sample seal procedures for the field blanks.
TOTAL DUST
Collect total dust samples using pre-weighed polyvinyl chloride (PVC) filters at a maximum flow rate of 2 liters per minute (L/min) for a maximum sampling time of 480 minutes or 8 hours. Be careful not to overload the filter. See the discussion on filter overloading in Section III. General Monitoring Requirements and Guidelines, Sampling Protocol section of this document.
RESPIRABLE DUST
Collect respirable dust samples using a clean Dorr-Oliver cyclone and a pre-weighed PVC filter at a flow rate of 1.7 L/min for a maximum sampling time of 480 minutes (see Figures II: 1-1, II: 1-2, and Appendix II Figure II: 1-18). Appendix II: 1–5 contains cyclone assembly and cleaning instructions. Be careful not to overload the filter. Make certain that the cyclone inlet (vortex finder) faces away from the person being monitored."
https://www.osha.gov/dts/osta/otm/otm_ii/otm_ii_1.htmlThere is more at the link. There are also different methods officially recognized by the United States Department of Labor which may be of value for possible judicial suit cases.
Unfortunately, there was no hint how to test air samples for barium, strontium or titanium. Probably Kristen Meghan might help as an expert.
