July 2005
Coal Services Health and Safety Trust Project No. 20083 - Final Report
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CONTENTS
Contents
Abstract
Introduction
Initial research of the continuous dust monitor
Description of the PDM
TEOM mass sensor
Data screen display
How it samples
Evaluation of the R&P personal dust monitor (PDM) in Australia
Coal Services NSW trial mine site
Training
Sampling Methodology
Instrumentation
Field Data Recording Sheets
In-mine Testing
Gravimetric Analysis
Results
Statistical Analysis of Results
Comments
Conclusion
References
Acknowledgments
FIGURES
1. PDM internal components
2. PDM connected to docking station for charging and communication with a PC
3. Basic PDM screen display formats and information presented
4. Technician changing filter on the PDM mass sensor
5. Coal Services – Dust Monitoring Logsheet
6. Technician wearing PDM and two cylones
7. Location of helmet mounted inlet for samples
8. Pump on charge between shifts
9. Unloaded cyclones and filters prior to gravimetric analysis
10. Technician weighing filters
11. Results of Table 1 presented graphically
12. Results of Table 2 presented graphically
13. Results of Table 3 presented graphically
14. Example of PDM data printout
TABLES
1. Results of samples compared to PDM 139
2. Results of samples compared to PDM 118
3. Results of all samples
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The National Institute for Occupational Safety and Health (NIOSH) in the USA, through an informal partnership with industry, labour, and the Mine Safety and Health
Administration (MSHA), has developed and tested a personal dust monitor (PDM) that provides near real-time respirable dust results.
Following the completion of laboratory and mine testing in the USA two instruments were made available to allow some comparative testing in Australia. This testing was carried out in NSW by the Coal Services Health Environmental Monitoring Service and this report details the project parameters, sampling methodology and results of testing.
This report presents the theory of operation, description, performance of the PDM compared to gravimetric-based reference dust sampling methods, and functionality of the instrument when used by miners. We specifically address the accuracy of the instrument before and after mine testing and the in-mine precision.
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Measurement of workplace dust is an essential first step in eliminating lung disease caused by overexposure to dust. The Coal Mine Health & Safety Act of 2002 in conjunction with the Coal Mine Health & Safety Regulation 2006, mandates that coal mine dust levels be monitored and controlled to at or below 2.5 mg/m
3 for a shift. To date, this monitoring process has relied upon personal sampling pumps and respirable dust cyclones to collect a filter sample in the mine environment. The filter is then analysed in a laboratory and the results returned to the mine operators several days or in relation to silica results, several weeks after the actual sample was taken.
In 1996 the National Institute for Occupational Safety and Health (NIOSH) commenced research to improve sampling instrumentation for use in the mining industry. In consultation with labour organisations, industry bodies, and government departments,
NIOSH issued a contract to Rupprecht and Patashnick Co., Inc. (now Thermo Electron
Corp. (TEC)), Albany, NY, to develop a one-piece personal dust monitor (PDM). The
PDM is based on an environmental ambient air monitor. The important aspect of this monitor is that it directly measures the mass of dust on a filter regardless of dust composition, size, or physical characteristics. This contract work successfully miniaturized the air quality monitor’s sensor and incorporated the sensor into a prototype personal dust monitor that provided accurate end-of-shift (EOS) data to miners
[Volkwein et al. 2004].
Laboratory and mine test results from initial testing demonstrated that the PDM was convenient to wear and robust to use, provided accurate and timely data, that could be used to monitor and prevent overexposure, and was easy to use.
Encouraged by the results from the initial laboratory and in-mine tests of the prototype and pre-commercial PDM units in the USA, an approach was made by members of the
Standing Committee on Dust Research and Control in NSW to assess the availability of one or more PDM’s for evaluation in Australia.
This report includes the first test results undertaken in Australia as part of Coal Services desire to assess the practicality of a potential new technology in assessing personal dust exposure and the level of conformity with existing methods.
This assessment involved no in-house laboratory testing as NIOSH had undertaken extensive testing in the US and Coal Services had no reliable testing equipment for delivering dust for collection in a sealed environment.
The testing included an underground evaluation that includes measurement of the precision of the PDM, against existing monitoring techniques in a longwall mine. The underground evaluation determined the performance of the PDM while in routine use by miners. The intent was to determine the equivalency of the PDM to Australian Standards
AS2985-2004.
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In 1997 the Joint Coal Board (now Coal Services) Health & Safety Trust granted funding for an evaluation of a real time dust sampling device which utilised the technology of the tapered element oscillating microbalance (TEOM) continuous respirable dust monitor that was being developed in the USA. The research funding was to evaluate whether the
TEOM continuous respirable dust monitor was suitable for application in Australian coal mines and would it provide useful data to control employee exposure to respirable coal dust, under Australian conditions? The project was in two stages the first stage being for two members of the SDC to visit the USA to technically evaluate the suitability of this instrument for use in Australia. At the conclusion of this technical evaluation a decision would then be made whether to proceed with the second stage, an operational evaluation of the instrument under Australian conditions.
In 1998 Brian Davies and Denis Glover visited the USA and reported the following:
The TEOM technology as developed by Rupprecht & Patashnick Co., Inc. (R&P) appears to be excellent and may well be the basis of all dust monitoring in the future, especially if a miniature personal monitoring device is developed.
Technical evaluation of the continuous dust monitor (CDM) in the USA was not as advanced as expected, giving rise to serious concerns for stage two, the purchase of an instrument for trials in Australia.
An offer of a spare CDM instrument from the National Institute of Occupational
Safety & Health (NIOSH) was a possibility for trials in Australia.
In 1999 NIOSH decided not to provide additional funding towards the future development of the machine mounted CDM and concluded the following:
The machine mounted CDM cannot be used to accurately represent mine workers exposure to respirable dust.
The instrument’s accuracy could not be determined by underground mine testing; however between working shifts the variability was approximately similar to gravimetric personal samplers.
For a further test program to be considered, the reliability of the machine mounted
CDM must be significantly improved.
An evaluation of the CDM in Australia was therefore not going to proceed. Although the
USA was switching focus to incorporating the CDM technology into a personal sampling device and if this occurred an Australian coal industry evaluation was possible.
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The PDM is intended to be a replacement for the cap lamp and battery currently used in mines. It is essentially a respirable dust sampler and cap lamp with dimensions and weight similar to those of a current PED-type miner’s cap lamp and battery. The PDM as tested weighed 3.0 kg
The key components of the device include a sample inlet tube, Higgins-Dewell cyclone
(similar to that used currently for respirable dust sampling), an air heater, pump, dust sensor (TEOM), two lithium-ion batteries for the sampler and the cap light, electronic control and memory boards, a display screen, and Windows®-based computer interface software called WinPDM. Figure 1 (below) shows some of these components.
Figure 1. – Exploded view of PDM components.
The case of the PDM is designed to meet drop test requirements for cap lamps and intrinsic safety-type approval requirements in the U.S., (although application for these has not occurred in Australia to date).
The PDM system also includes a docking station used to communicate with PC software for programming and retrieving stored data in the instrument and to recharge its batteries
(see Figure 2).
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Figure 2. – PDM connected to docking station – used to charge batteries and communicate with PC.
The tapered-element oscillating microbalance (TEOM) mass sensor is the key to the
PDM. The TEOM mass sensor is a hollow tube, called the tapered element, which is clamped at its base and free to oscillate at its narrow end. A replaceable filter cartridge is mounted on its free end collects the respirable dust particles contained in the airstream that passes from the entrance of the mass sensor through the tapered element.
Electronic components positioned around the tapered element cause the tube to oscillate at its resonant frequency and at constant amplitude in much the same fashion as a tuning fork. As the respirable dust collects on the filter, the natural oscillation frequency decreases. This change in frequency (determined by the mass of dust) is divided by the air volume sampled during the same period to provide a dust concentration reading, shown in milligrams per cubic meter, every few seconds.
The PDM displays dust exposure information to the miner in both numeric and graphic formats (see Figure 3 below) and can store approximately 20 full-shift samples in its memory. These data may be selected for downloading and analysis.
The illuminated data display on the top of the PDM continuously shows the previous 30 minute average dust concentration, the cumulative mass concentration to that point in the shift, and an estimated end-of-shift (EOS) projected concentration exposure.
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Figure 3 – Basic screen display formats – graphic – right; numeric - left
An air sampling pump within the PDM draws air from the mine atmosphere at a flow rate of 2.2 L/min via an inlet mounted adjacent to the cap lamp on the hard hat and passes through conductive tubing before reaching the cyclone at the entrance of the PDM. The cyclone separates the dust and allows respirable dust to proceed through a heated section of tubing to remove excess moisture and then to enter the PDM’s mass sensor.
A filter cartridge collects the respirable particles as the air passes through the TEOM sensor. The mass sensor can be removed from the PDM by a technician (see Figure 4 below) to change the particle collection filter and clean the unit after the end of each sampling period or shift.
Figure 4 – Technician changing filter on the mass sensor
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A project team from the Coal Services SDC was established in 2002 to progress the possibility of the evaluation of the PDM in Australia, as R&P had successfully developed
TEOM technology into the PDM. A proposal was to reactivate the original Health &
Safety Trust funding for an Australian evaluation and formalise arrangements with R&P to obtain instruments for trial in Australia.
The Health & Safety Trust project aims were as follows:
Introduce the R&P Inc PDM to operators, employees and other stake holders in the NSW coal industry.
In investigate the relationship between respirable dust concentration measurements on underground coal miners using the PDM and the current statutory measurement technique used in NSW (AS 2985-2004). Undertake both lapel and helmet sampling locations.
Evaluate the reliability, field worthiness and technical value of the PDM under
Australian coal mining conditions.
Agreement on sampling protocol was finally settled with R&P and NIOSH in 2004.
Three PDM instruments arrived in Australia in April 2005. Initially the intention was to seek NSW Government Inspectorate temporary approval for the PDM and cap lamp at the trial mine site. The application was not progressed due to incomplete tests to satisfy
IEC 60079 part 0 &11 and AS/NZS 62013-2001. The instrument manufacturer or his agent will probably apply in the future for the overall approval to use the PDM in NSW underground coal mines.
The Australian Coal Association Research Program (ACARP) also granted funding to
Stewart Gillies – Gillies Wu Mining Technology Pty Ltd for a project on using the PDM for personal respirable dust evaluation particularly in engineering studies. The objective of this study is to evaluate the PDM in its capability as an engineering tool to quickly and accurately measure changes to longwall dust levels at operator locations after implementation of a dust control improvement. The project was undertaken over 4 months from April to July 2005. (Gillies, 2005)
West Wallsend Colliery was chosen due to the low prevalence of flammable gas. Under the Coal Mines (Underground) Regulation 1999 the mine electrical engineer allowed the use of the PDM’s during the trial period as non-approved portable electrical apparatus
(NSW Govt,1999). Longwall mining was chosen for the trials due to accessibility and the potential for high dust concentrations. Due to longwall goaf caving restrictions and wind blast controls the PDM trial start was delayed until June 2005 and the number of samples collected was less than originally planned.
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The PDM units were delivered the Coal Services Argenton laboratory where training was supplied by Richard McCabe Durham, Engineering Technician for R & P. This consisted of
0.5 hours
2.0 hours
Background to PDM development
Detailed discussions on components and how PDM works
2.5 hours
1.5 hours
PDM usage, download and data analysis
Comments from NIOSH and MSHA tests to date.
This covered of all sampling practices, charging, programming, and maintenance procedures, cleaning, downloading and interpretation of data that were required to undertake the project. A number of trial laboratory runs were conducted to ensure that all relevant staff were conversant with the practical use and maintenance of the PDM units.
All samples were conducted at the West Wallsend Colliery Longwall with the PDM samplers and additional pumps and cyclones worn by Coal Services Technicians.
The PDM unit was programmed for crib room to crib room sampling as per the current practice in NSW underground coal mines. The Coal Services (CS) Health sampling technician was required also to wear two additional Dupont P2500A sampling pumps and
Higgins-Dewel cyclones fitted with 25mm Gelman GLA500 5um PVC filters.
One cyclone was attached to the lapel, and the other cyclone was fitted with a tube extension to sample adjacent the PDM sampling inlet point on the helmet at the cap lamp, all samples in the breathing zone as per AS 2985-2004. This was done to not only assess the accuracy of the PDM against the traditional sampling technique but also to assess whether the location of the air inlet adjacent to the cap lamp significantly altered dust reading in relation to the traditional lapel located cyclones.
The instrumentation used for the monitoring program included:
Dupont P2500A Air sampling pumps: serviced and calibrated January 2005.
Pump rates set at 2.2 litres per minute (respirable).
Cassella (Higgins Dewell) cyclone sampling heads fitted with 25mm PVC filters.
Rupprecht & Patashnick Model 3600 PDM’s. (Pre-commercial units).
The calibration of all pumps was checked prior to and following sampling using a
Cassella rotameter (flowmeter).
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The full details of each sampling work location, mining equipment, work task and ventilation readings were recorded in the dust monitoring log sheet as per Figure 5 below.
Figure 5 – Dust monitoring logsheet
These log sheets were used to identify primary tasks and conditions occurring throughout the sampling shift that influenced the dust results that would be reflected in the PDM display and subsequent printout and graphs. Much of this data is traditionally recorded during a statutory sample to assist in explaining the result; however the current method of sampling does not determine when the exposure occurred during the shift.
Once the data from the PDM was downloaded, the timing of some of these ‘events’ was plotted against the graphs to assess the suitability of using the PDM to assist in modifying behaviour eg operator positioning to reduce exposure to dust.
Due to the impost of having to wear three pieces of equipment, only Coal Services technicians were utilised in the testing, although throughout the shift they ‘shadowed’ operational personnel to approximate actual exposure on the shifts tested. All samples were undertaken at West Wallsend Colliery on Longwall 31.
Two CS Health sampling technicians collected 18 sets of samples over a 3 week period commencing on 6 th
of June 2005. Only 2 PDM units were used during the evaluation trials. Figure 6 over page shows one of the technicians fitted up for the shift.
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Figure 6 - Technician wearing PDM and two cyclones
Sampling was conducted over a minimum period of 4 hours and a maximum period of seven hours. The sampling did not include travelling time into the Longwall face as is the practice for sampling under the Coal Mines Health and Safety Regulation.
At the end of each shift the PDM units and all sampling equipment was conveyed to the
CS Health Argenton laboratory where information from the PDM’s was downloaded. The technician would clean the inlet tube and cyclone, change the filter, and place the PDM on charge for the next shift of sampling.
The Dupont pumps were cleaned and placed on charge for the next shift while the cyclones were unloaded, cleaned and reloaded with new pre-weighted filters for the next shift.
Figure 7 - Location of helmet mounted inlet for samples
Coal Services Health and Safety Trust Project No. 20083 - Final Report
Figure 8 – Pumps on charge between shifts
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The exposed filters were placed in petri dishes and left for a minimum of eight hours to equilibrate with the blanks before gravimetric analysis.
Figure 9 - unloaded cyclones and filters prior to gravimetric analysis
The paired results of filters for each shift of sampling were analysed gravimetrically and the results compared to those returned from the PDM. The gravimetric analysis was performed on a Mettler 3M microbalance for the traditionally collected respirable dust samples. Weighing was done in the Coal Services Argenton NATA accredited laboratory.
All samples were pre- and post weighed using control (blank) filters. Average blank control filter weights were used to correct the filter mass results for each test.
Gravimetric analysis was not conducted on the filters from the PDM, however results were compared to those supplied from the downloaded data from the equivalent shift and person sampled.
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Figure 10 - Technician weighing filters
All results were double checked and recorded to two significant figures for comparison with the results downloaded from the PDM’s. Note that analysis was conducted for dust only as the filters from the PDM were unable to be analysed for quartz. This is a problem that is being addressed by the manufacturer, and would be considered a critical requirement for use particularly in the Northern district coalfields of NSW.
The table on the follow page provides the comparative test results for the eighteen samples conducted as part of this study. The results are presented in tabular form for the three sets of result undertaken by each sampler on the day and are identified by the PDM sampler worn ie PDM139 and PDM 118 which are the manufacturers identification numbers. Following the table of each set of results is presented graphically to provide a visual interpretation of results.
PDM 139
Date Sample No. Result - PDM Result - lapel Result - helmet
6.06.05
7.06.05
8.06.05
15.06.05
N064/05
N065/05
N070/05
N072/05
1.06
0.91
0.86
0.59
16.06.05
22.06.05
23.06.05
24.06.05
N075/05
N079/05
N081/05
N083/05
1.03
1.22
1.02
1.01
Table 1 – Results of samples compared to PDM 139
1.45
0.88
0.69
0.58
0.94
1.44
1.00
0.30
1.08
0.93
0.62
0.63
0.92
1.40
0.91
1.62
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
6.
06
.0
5
7.
06
.0
5
8.
06
.0
5
15
.0
6.
05
16
.0
6.
05
22
.0
6.
05
23
.0
6.
05
24
.0
6.
05
Figure 11 – results of Table 1 presented graphically
Coal Services Health and Safety Trust Project No. 20083 - Final Report
PDM 139
Lapel Sample
Cap Sample
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PDM 118
Date
6.06.05
7.06.05
8.06.05
9.06.05
15.06.05
16.06.05
17.06.05
22.06.05
23.06.05
Sample No.
N063/05
N066/05
N069/05
N071/05
N073/05
N076/05
N077/05
N078/05
N080/05
Result - PDM
0.9
0.8
0.6
0.55
0.45
0.98
1.23
1.09
0.83
24.06.05 N082/05 0.77
Table 2 – Results of samples compared to PDM 118
Result - lapel
1.42
0.80
0.74
0.67
0.57
0.96
1.3
1.36
0.95
1.04
Result - helmet
1.49
0.97
0.69
0.58
0.57
0.83
1.34
1.44
0.84
0.74
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
6.
06
.0
5
7.
06
.0
5
8.
06
.0
5
9.
06
.0
5
15
.0
6.
05
16
.0
6.
05
17
.0
6.
05
22
.0
6.
05
23
.0
6.
05
24
.0
6.
05
PDM 118
Lapel Sample
Cap Sample
Figure 11 – results of Table 2 presented graphically
As can be seen the results tended to follow a general pattern, with some sample showing good correllation and others exibiting some apparantly significant differences. A further table and graph pulling together all the results is presented before a statistical analysis of the results is given.
All of the results were tabulated for the dates they were sampled and graphed for exposure. Other than some unexplained significant differences on the final day of sampling the results were relatively consistant, as shown below in Table three and the corresponding graph – Figure 12.
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Full Results
Date
6.06.05
7.06.05
8.06.05
9.06.05
15.06.05
16.06.05
17.06.05
22.06.05
23.06.05
PDM 139
1.06
0.91
0.86
0.59
1.03
1.22
1.02
24.06.05 1.01
Table 3 – Results of all samples
Lapel
Sample
1.45
0.88
0.69
0.58
0.94
1.44
1
0.3
Cap
Sample
1.08
0.93
0.62
0.63
0.92
1.4
0.91
1.62
PDM 118
0.9
0.8
0.6
0.55
0.45
0.98
1.23
1.09
0.83
0.77
Lapel
Sample
1.42
0.8
0.74
0.67
0.57
0.96
1.3
1.36
0.95
1.04
Cap
Sample
1.49
0.97
0.69
0.58
0.57
0.83
1.34
1.44
0.84
0.74
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
PDM 139
Lapel
Sample
Cap
Sample
PDM 118
6.
06
.0
5
7.
06
.0
5
8.
06
.0
5
9.
06
.0
5
15
.0
6.
05
16
.0
6.
05
17
.0
6.
05
22
.0
6.
05
23
.0
6.
05
24
.0
6.
05
Date
Lapel
Sample
Cap
Sample
Figure 12 – results of Table 3 presented graphically
A statistical review of results was inconclusive as the precision of the eighteen results was not very good and that means that the sample size needs to be quite large to make valid statistical determination on the accuracy of the PDM in relation to the current sampling methodology.
It should however be stated that as is indicated on the graph above there is sufficient correlation of results to indicate that the sampling methodologies could be considered qualitatively similar and the PDM worthy of further study as a replacement technology for current sampling techniques.
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The PDM unit was comfortable to wear compared to the traditional cap lamp battery pack due to the curved design despite being slightly larger and heavier. The programming and down loading of data from the PDM was relatively easy to operate. Indicative results of dust exposure highlighted the importance of operator location in relation to dust levels.
An example of a printout of the PDM with some comments added to the graph is shown below in Figure 14.
Figure 14 – Example of PDM printout
There was some interest expressed by miners working at the Longwall face during the study in respect to the results provided a reminder of the role of operator location in respect to dust exposure, and that being incorporated into the cap lamp battery, the sampler would not impact upon their work the way the current sampling method does.
The comparative results show some promise, however further testing at a number of different mines, seams and environmental conditions is required to provide statistically valid data for a true comparison with the current gravimetric method of sampling. When the PDM unit is fully approved for use in underground coal mines in NSW, Coal Services
Health should plan to obtain a number of the PDM units and under take that further evaluation.
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Coal Services 2004, Annual Report 2003 - 04. Coal Services Pty Limited: Sydney
Coal Services 2005, Australian Black Coal Statistics 2004. Coal Services Pty Limited:
Sydney
Gillies 2005, Queensland Mining Industry Health & Safety Conference: Townsville,
August 2005
NSW Govt. 2001 Coal Industry Act 2001. NSW Govt. Printer: Sydney
NSW Govt. 1984 Coal Mines Regulation Act 1982 No 67. NSW Govt. Printer: Sydney
NSW Govt. 1999 Coal Mines (Underground) Regulation 1999. NSW Govt. Printer:
Sydney
Rupprecht and Patashnick Co. [2004]. Operating manual, TEOM series 3700/3700 personal dust monitor, revision A, September 2004, R&P part number 42–009904.
Albany, NY: Rupprecht and Patashnick Co., Inc.
Volkwein JC, et al, [2004]. Performance of a new personal respirable dust monitor for mine use. Pittsburgh, PA: U.S. Department of Health and Human Services, Public Health
Service, Centers for Disease Control and Prevention, National Institute for Occupational
Safety and Health, DHHS (NIOSH).
Volkwein JC, et al, [2006]. Laboratory and Field Performance of a Respirable Personal
Dust Monitor. Pittsburgh, PA: U.S. Department of Health and Human Services, Public
Health Service, Centers for Disease Control and Prevention, National Institute for
Occupational Safety and Health, DHHS (NIOSH).
The authors thank and acknowledge the support and technical advice provided by
West Wallsend Colliery management and employees for their invaluable assistance throughout the PDM evaluation project.
CS Health Environmental Monitoring Group, especially Glenn Goodwin and
Mark Shepherd for all of the underground dust sampling
Dr Brian Davies – AEHS, for help with the PDM project design, instrument procurement and project review.
Erich Rupprecht, Business Development Manager, and Dan Dunham, PDM
Project Manager, from Thermo Electron Corp.
Jon Volkwien and NIOSH for advice, support and providing many of the photographs and details for the description of the PDM.
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