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U.S. Department of Labor

Mine Safety and Health Administration
201 12th Street South, Suite 401
Arlington, VA 22202-5450
ISSUE DATE: May 16, 2011
LAST VALIDATED: 03/31/2021


FROM:             KEVIN G. STRICKLIN  
                       Administrator for
                       Coal Mine Safety and Health

                      Administrator for
                      Metal and Nonmetal Mine Safety and Health

                      LINDA F. ZEILER LINDA F. ZEILER
                       Acting Director of Technical Support

SUBJECT:     Re-Issue of P02-04 - Potential Health Hazard Caused by Platinum-
                    Based Catalyzed Diesel Particulate Matter Exhaust Filters

This Program Information Bulletin affects underground coal and metal and nonmetal mine operators using diesel-powered equipment, manufacturers of diesel-powered underground mining equipment, including exhaust after-treatment devices and systems, 'miners' representative' and Mine Safety and Health Administration (MSHA) enforcement personnel.

The purpose of this bulletin is to inform mine operators of a potential health hazard caused by currently available platinum-based catalyzed diesel particulate matter (DPM) exhaust filters for diesel-powered equipment. Use of these type filters may result in increased production of nitrogen dioxide (NO2) gas, as compared to N02 emissions produced by engines operating without these type filters, causing miners to be exposed to increased concentrations of NO2. Symptoms of overexposure to NO2 include irritation to the eyes, nose and throat, cough, decreased pulmonary function, chronic bronchitis, breathing difficulty, chest pain, pulmonary edema, and rapid heartbeat.

The MSHA standard at Title 30, Code of Federal Regulations, Section 72.501 (30 C.F.R. § 72.501) establishes a schedule requiring that coal mine operators meet certain emission specifications for nonpermissible heavy-duty diesel-powered equipment in underground coal mines. At 30 C.F.R. § 57.5060, MSHA requires operators of metal and nonmetal underground mines to limit DPM concentration where miners normally work or travel. Mine operators most likely have to use DPM filters to meet these MSHA requirements.

A common type of DPM filter is the ceramic (Cordierite® or silicon carbide) wall-flow monolith. These filters are either catalyzed (containing precious or base metal) or non-catalyzed. Catalyzed filters offer the advantage of low-temperature on-board regeneration (removal of trapped soot from the filter) accomplished through the utilization of exhaust gas heat. Non-catalyzed or base metal catalyzed filters may require removal from the machine for cleaning, but may, in some cases, be regenerated on board.

In addition to DPM standards, the concentration of NO2 in underground mining environments may not exceed a ceiling value of 5 parts per million (ppm) as established in MSHA standards at 30 C.F.R. § 57.5001 (Metal/Nonmetal) and 30 C.F.R. § 75.322 (Coal).

'This program information bulletin is updated with current contact persons' information.'

Thus far, MSHA has tested six precious metal (platinum) catalyzed filters at its diesel laboratory and has determined that each of them increases the amount of NO2 emitted by one MSHA-approved diesel engine, as compared to the same engine operating under identical test conditions, but without the catalyzed filter. The increase is attributed to the oxidation of nitric oxide (NO) due to the presence of the platinum catalyst. The concentrations of NO2 obtained through the installed platinum catalyzed filters reached levels that could not be diluted to or below 5 ppm using the engine's approved gaseous name plate air quantity. The gaseous name plate air quantity is the amount of ventilation air necessary to reduce the engine emission gaseous concentrations to or below these specified levels: NO to 25 ppm, NO2 to 5 ppm, CO (carbon monoxide) to 50 ppm and CO2 (carbon dioxide) to 5000 ppm based on a laboratory test cycle. This air quantity is listed on the engine's approval plate which is attached to the engine.

MSHA will continue to test additional filters and release the results to the mining community. Manufacturers are developing catalyst formulations which may overcome the NO2 problem, possibly by lowering the platinum content of the traps or by using other catalytic formulations. MSHA maintains a list of manufacturers who can supply filters on its Internet web site at:

Note that MSHA has included a cautionary statement on this list concerning the potential health hazard associated with the available catalyzed DPM filters. The listed manufacturers can assist the mine operators in selecting a filter system to meet MSHA requirements. Please contact MSHA Technical Support for additional information on DPM filters.

Recommended Action
To determine whether the catalyzed filter is causing an increase in NO2 that might adversely affect the mine's air quality, the machine should be operated in an entry that provides the engine's name plate air requirement, or the minimum quantity of air that the machine can work in. The machine should be operated under its normal working cycle and NO2 levels should be monitored downstream from the machine. The NO2 concentration should not exceed 5 ppm when tested. MSHA representatives are available to assist mine operators with this test.

Platinum-based catalyzed DPM filters that cause a MSHA-approved engine or a non-approved engine to produce NO2 emission levels that cannot be diluted to or below 5 ppm, utilizing either the:

Federal Mine Safety and Health Act of 1977; 30 C.F.R. Parts 7, 36, 57, 72 and 75.

Issuing Offices and Contact Persons
Mine Safety and Health Enforcement, Health Division
Greg Meikle, (202) 693-9523

Technical Support, Approval and Certification Center
Jeffrey Moninger, (304) 547-2324

Phillip McCabe, (304) 547-2315

Internet Availability
This information bulletin may be viewed on the Internet by accessing MSHA's home page at and choosing"Compliance Info"and "Program Information Bulletins."

All Program Policy Manual Holders
Mine Operators
Independent Contractors
Special Interest Groups