Spark Arrester Guide


Frequently Asked Questions


General Questions about Spark Arrester Guide

General Purpose

Locomotive 

Multiposition Small Engine (MSE)


General Questions about Spark Arrester Guide

What is a Spark Arrester?

A Spark Arrester is a device which traps or pulverizes exhaust carbon particles to a size below 0.023-inch in diameter, as they are expelled from an exhaust system. Trap type Spark Arresters must have a method for removal of accumulated carbon particles. Most spark arresters generally perform in the high 90 percent spark arresting effectiveness range.
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What about updates to the SAG?

Testing of newly submitted spark arresters is an ongoing process at SDTDC. The Center will be responsible for notifying SAG users of newly qualified and rated spared arresters. SDTDC will send the information to appropriate Regional and State offices for their distribution. Users should contact these sources for updated information. SAG Updates are usually mailed via DG in July & December.

For quick reference, updates should be inserted in the publication font the appropriate type arrester. These new qualified arresters will be included with illustrations when the Guides are reprinted.
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What about reprint information?

SDTDC will determine when adequate information has been compiled to require a reprinting of each publication. The Center will notify the Regional and State offices when a reprinting is available. Ti is anticipated that a reprinting may be required on odd numbered years for the Multiposition Small Engine (MSE) Guide and on even numbered years for the General Purpose and Locomotive (GP&L) Guide.
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What should I do with Discontinued Models?

Discontinued Models will be called out under "Remarks."
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General Purpose and Locomotive (GP&L)

What is the General Purpose and Locomotive Spark Arrester Guide?

The General Purpose and Locomotive Spark Arrester Guide is a compilation of information, lists, and illustrations of qualified GP&L spark arrester systems and engines - including their identifying markings, design, and assembly.

The intent of the SAG is to provide field inspectors with adequate information to determine if an engine and exhaust system combination have been tested and qualified by the San Dimas Technology and Development Center (SDTDC) as meeting the Standard for spark arresting exhaust systems.

The SAG is printed as two publications. This SAG covers General Position & Locomotive (GP&L) arresters, and the other SAG covers Multiposition Small Engine (MSE) arresters.

In each publication, there is a section for each type of arrester with illustrations of spark arresters listed in alphabetical order by the manufacturer's name, and lists of qualified and rated spark arresters of that type. Inspectors can use these sections to verify qualification status. Specific instructions for use of each section precedes the section.

Use of the SAG is also illustrated in the video "Spark Arresters and the Prevention of Wild land Fires" and may be used as a supplemental instruction tool. The video contains five separate modules titled, "Introduction, Multiposition Small Engine, General Purpose, Off Highway, and Railroad".

The two SAG publications and the video may be ordered, by purchase or requisition, from:

National Interagency Fire Center (NIFC)
Attn: Great Basin Cache, Supply Office
3833 S. Development Avenue
Boise, ID 83705
FAX: 208-387-5573
You will be billed within 30 days of shipping.

Order numbers are:
NFES 2363 - Multiposition Small Engine Spark Arrester Guide (MSE) Volume 2, June 1997
NFES 1363 - General Purpose and Locomotive Spark Arrester Guide (GP/LOCO) Volume 1, April 1998
NFES 2237 - Spark Arresters and the Prevention of Wild land Fires, (video) May 1998
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What is a General Purpose Spark Arrester?

General Purpose Spark Arresters are tested against USDA Forest Service Standard 5100-lb or the latest revision of Society of Automotive Engineers (SAE) Recommended Practice SAE J350. Either of these documents establish the minimum performance and maintenance requirements of single-position application general purpose spark arrester. Spark arresting effectiveness shall be at least 80 percent for all flow rates on the cold test which correlates to 90 percent on a hot engine.
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What is a Screen-Type Spark Arrester?

Screen-Type Spark Arresters as defined by USDA Forest Service Standard 5100-lb fall into a special category. They are intended for use on small engine applications. All exhaust products must pass through the screen, which has openings of 0.023-inch or less. the effective exhaust area of the screen (total area of all screen openings) shall not be less than 200 percent of the engine exhaust port area at its smallest cross-section. Screen material shall be heat and corrosion resistant, and shall provide at least 100 hours of service life. These are originally qualified for all the positions described in the "Application Positions" section.
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What is an "Add-On" Spark Arrester?

" Add-On" Spark Arresters are added onto an existing muffler exhaust system. They are typically used on Off-Highway-Vehicles. Add-on spark arresters must have a method for removal of accumulated carbon particles. Such as a cleanout plug, snap ring, removable end cap or a removable end cleanout. A removable end cleanout is usually secured to the muffler by a retaining band and/or several screws. In order to empty out the accumulated carbon particles with a removable end cleanout, the entire add-on must be removed by loosening the retaining band or screws, to shake out the carbon particles.
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What are Application Positions?

Application Positions consist of four general positions - vertical, horizontal, inverted, and multiposition. The application is determined by the attitude of the inlet pipe irrespective of the main body position or direction of outlet. For Example: The qualified positions listed include only those tested. In some cases, the manufacturer may claim other positions, but test information at this time neither support or refute such claims. An arrester tilted more than 60 degrees from its qualified operating position may not adequately arrest sparks. Therefore, arresters on mobile equipment - other than screen type arresters - shall not be mounted more than 45 degrees from the qualified position. See column marked "Appl Pos."
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What is the Rated Flow of Arrester?

Rated flow of Arrester is the rate of test gas flow in cubic feet per minute at which the corresponding back pressure is 1 pound per square inch. This is the maximum desirable back pressure for most four-stroke cycle applications. See column marked "Flow." Note: General Purpose Screen Type Spark Arresters are limited to the listed rated flow, 2 or 4 cycle, and horse power.
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Do Turbochargers qualify as effective Spark Arresters?

Turbochargers qualify as effective spark arresters when 100% of the exhaust gasses pass through the turbine wheel. The turbine wheel must be turning at all times and there must be no exhaust bypass to the atmosphere. Depending on design, small enclosed system bypasses that reroute some exhaust back through the engine may be allowed. The illustration of the exhaust-driven turbocharger shows the air intake and the exhaust path through the turbine wheel. The action of the rotating turbine wheel causes carbon particles to remain within the confines of the turbo-drive section until they are reduced to a harmless size by attrition.
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How should Clean my Arrester?

The arrester shall have provision for the easy disposal of the accumulated particles without removal of the clamping or mounting devices from the stack, pipe, or manifold assembly. Screen-type devices shall provide for the easy removal and cleaning or replacement of the screen.
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What about Marking and Labeling?

Each arrester shall be permanently marked with the manufacturer's model number designation and a trademark or other identification or manufacturer. Where an inverted installation is possible, the inlet or outlet shall also be marked. In addition to the above markings, screen-type devices must have the words "Screen Type" clearly imprinted in 1/8-inch or larger letters. the model number must match exactly. The words "Qualified" or "Approved" are not required, and do not indicate that the unit is in fact a qualified arrester.
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How do I inspect a General Purpose Spark Arrester?

Standard 5100-lb requires that each arrester shall be permanently marked with the model number and the manufacturer's name or trademark. The model number must match exactly. The identification must be stamped in the metal body or on a attached metal plate. The words "Qualified" or "Approved" are not required, and do not indicate that the unit is in fact a qualified arrester.

  1. If identification of the manufacturer's name and model number is found, then refer to the "Qualified and Rated" list.
  2. Check the "Qualified and Rated" list to establish if the arrester is qualified.
  3. If not on the "Qualified and Rated" list, be sure to check any SAG update information you have received since the time of the printing of your present SAG. The absence of an arrester from these lists indicates that the arrester has not been qualified.
  4. After the arrester has been identified, turn to the Drawing Section and check the spark arrester illustration for an exact match on the configuration, dimensions, and cleanout devices. The drawing must match the spark arrester you are inspecting.
  5. Suggested tools for inspections:
    1. Hand tools to open cleanout, screwdriver and pliers
    2. Flashlight
    3. 1/8-inch wire rod or stick to probe inside the arrester to determine if stationary fan or vanes are in place
    4. Tape measure
    5. 0.024-inch wire gauze to determine screen size
  6. Inspect to ensure that:
    1. The spark arrester is correct for the position of application.
    2. The exhaust system between the engine and the spark arrester is in good order.
    3. The arrester is properly maintained and cleaned out when necessary.
    4. There are no modifications to the exhaust system.
  7. More detailed instructions are available in the NWCG video, "Spark Arresters and the Prevention of Wildfires".
  8. Follow your agency policies when an unqualified spark arrester system is encountered.

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Basic Definitions List:

Exhaust Particles - All internal combustion engines produce exhaust particles which are predominately carbon with contaminates. These particles originate from deposits formed on the internal surfaces of the engine or exhaust system and, depending on their exact origin, may be expelled at temperatures in excess of 3,000° F. Depending on the nature of the contaminates, these particles are capable of glowing or sometimes flaming combustion. When expelled through the exhaust system into the atmosphere, the combustion process may continue or even be accelerated during flight. Such particles, if larger than 0.023-inch in diameter and at temperatures of 1,200° F are capable of igniting cellulose materials upon contact.
 
Mufflers - Experience and tests have shown that mufflers, in general, are inadequate as spark arresters. Few muffler devices submitted for formal tests meet the requirements of 5100-lb or SAE J350. However, properly maintained baffled mufflers constructed to automotive industry standards, and installed on motor vehicles other than motorcycles are accepted for "on-highway" and "off-road" use in some jurisdictions. Exceptions are designated areas where a spark arrester is required on cross-country vehicles. Straight-through mufflers, such as glass-pack designs without baffles, are not acceptable. Consult your agency policy for more specific guidelines.
 
Exhaust Systems - The exhaust system consists of the manifold (on multicylinder engines), muffler or spark arrester on both, an exhaust pipe between the engine cylinder exhaust outlet port, and the end of the exhaust pipe which is open to the atmosphere.
 
Exhaust Manifold - A chamber into which the exhaust from each of the engine cylinders is collected. The exhaust is then directed out of the manifold to a muffler or spark arrester or both. Most large locomotive engines have the spark arrester designed into the exhaust manifold. Small, single-cylinder engines do not have manifolds.
 
Modification - Any modification or damage to any part of the system as it was presented to SDTDC for testing voids the qualifications of the spark arrester on the equipment. Modifications usually consist of removal of or damage to parts, change in exhaust outlets, replacing the fiberglass packing with steel wool, improper mounting, and bypasses.
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Locomotive 

What are standards for Locomotive-Type Spark Arresters?

Locomotive-type spark arresters are tested in accordance with the latest revision of the Association of American Railroads (AAR)
Recommended Practice RP-557, "Spark Arresters for Non-turbocharged Diesel Engines Used in Railroad Locomotives", Society of Automotive Engineers (SAE) Recommended Practice J342, "Spark Arrester Test Procedure For Large Size Engines," SAEJ997, "Spark Arrester Test Carbon", and USDA Forest Service Standard 5100-1 b, "Spark Arresters for Internal Combustion Engines."  These Standards and procedures establish the minimum performance and maintenance requirements for locomotive-type spark arresters.

EXTERNAL ARRESTERS are those designed to be installed on the locomotive exhaust stack or stacks. They may be inside or outside the engine compartment. SAE J350 or Forest Service Standard 5100-lb test procedures are used for this type arrester.
INTERNAL or MANIFOLD-TYPE ARRESTERS make use of the engine manifold and are installed below the locomotive profile.
This type arrester is tested against SAE J342 or ARR Recommended Practice, RP-557.
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What are Locomotive-Type Spark Arrester inspection procedures?

  1. Look for the locomotive manufacturer's name on the locomotive frame below the cab. 
    Note:
  2. If it has an arrester, look for the manufacturer's name and model number on the body of the arrester. They must be stamped on the metal body or on an attached metal plate. Internal arresters must be stamped in the metal body or on an attached metal plate affixed to the manifold.
  3. If identification is established, then check the "Qualified and Rated" list.
  4. If the arrester cannot be identified (i.e., tag missing), determine if the arrester is an internal arrester (manifold type), or an external arrester (generally mounted on the exhaust stack).
  5. Then turn to the locomotive identification section and check the illustrations for configuration of body type to identify make and model possibilities. 
  6. Check the "Qualified and Rated" pages to determine if it is qualified. (Note: The two most often found are FARR and HAPCO.)
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How do I inspect a Locomotive-Type Arrester?

  1. Turbocharged Locomotives 
    Inspect for carbon build-up on the eductor tubes and exhaust stack (no arrester is required).
      On muffler equipped locomotives, you will have to remove or have the eductor removed for inspection.
    (Note: The locomotive will have one exhaust stack.)
  2. Non-turbocharged Locomotives
      Inspect for correct application of arrester.
      Arrester properly cleaned and maintained.
      Exhaust system in good order.
    (Note: The locomotive can have up to four exhaust outlets and will require up lo four spark arresters). 
  3. Steam Powered Locomotives
      Inspect for a screen over the entire exhaust stack that has been maintained in good order.
    Check your agency rules and regulations. 
  4. Tools needed for an inspection:
      Miscellaneous hand tools
      Coveralls
      Gloves
      Goggles
      Flashlight
      Mirror
      Carbon particle collection containers
    More detailed instructions are found in the NWCG publication "Railroad Inspection Handbook", and the NWCG video, "Spark Arresters and the Prevention of Wildland Fires".
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How do I identify a Locomotive-Type Spark Arrester?

EXTERNAL SPARK ARRESTERS are fitted to the exhaust stack of a conventional locomotive exhaust manifold. They are identified by the manufacturers name and model number.  

INTERNAL or MANIFOLD-TYPE SPARK ARRESTERS have seven basic body variations referred to as Types I through VD.
Each of these body types may use one or more of four leg configurations referred to as A-swirl leg, B-bent leg, C-straight leg, or D-short straight leg. See the following pages for illustrations.  Qualified internal arresters may be redesigned manifolds or they may be originally designed as spark arrester manifolds. They can have any combination of body type and leg configuration
as shown on the following pages and as listed on the individual qualification. The appropriate model number will appear on the
spark arrester name plate and correspond to drawing numbers on file at SDTDC.

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Multiposition Small Engine (MSE)

What is the Multiposition Small Engine Spark Arrester Guide?

The Multiposition Small Engine Spark Arrester Guide is a compilation of information, lists, and illustrations of qualified MSE spark arrester systems and engines - including their identifying markings, design, and assembly.

The intent of the SAG is to provide field inspectors with adequate information to determine if an engine and exhaust system combination have been tested and qualified by the San Dimas Technology and Development Center (SDTDC) as meeting the Standard for spark arresting exhaust systems.

The SAG is printed as two publications. This SAG covers Multiposition Small Engine (MSE) arresters, and the other SAG covers General Purpose & Locomotive (GP&L) arresters.

In each publication, there is a section for each type of arrester with illustrations of spark arresters listed in alphabetical order by the manufacturer's name, and lists of qualified and rated spark arresters of that type. Inspectors can use these sections to verify qualification status. Specific instructions for use of each section precedes the section.

Use of the SAG is also illustrated in the video "Spark Arresters and the Prevention of Wild land Fires" and may be used as a supplemental instruction tool. The video contains five separate modules titled, "Introduction, Multiposition Small Engine, General Purpose, Off Highway, and Railroad".

The two SAG publications and the video may be ordered, by purchase or requisition, from:

National Interagency Fire Center (NIFC)
Attn: Great Basin Cache, Supply Office
3833 S. Development Avenue
Boise, ID 83705
FAX: 208-387-5573
You will be billed within 30 days of shipping.

Order numbers are:
NFES 2363 - Multiposition Small Engine Spark Arrester Guide (MSE) Volume 2, June 1997
NFES 1363 - General Purpose and Locomotive Spark Arrester Guide (GP/LOCO) Volume 1, April 1998
NFES 2237 - Spark Arresters and the Prevention of Wild land Fires, (video) May 1998
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What is a Multiposition Small Engine?

A Multiposition Small is defined by the Society of Automotive Engineers (SAE) Recommended Practice J335 as being a hand-held, internal combustion engine operable in more than one position. MSE configurations include, for example, such devices as chain saws, weed trimmers, brush cutters, blowers, hedge trimmers, and cut-off saws.
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How are Multiposition Small Engines Tested?

Testing of MSE's is conducted in accordance with the Society of Automotive Engineers (SAE) procedure J355. This provides the methods of testing to evaluate the fire ignition potential of exhaust systems used in MSE's. These methods include tests for screens, and surface and exhaust gas temperatures. Screens and mounting systems are checked for openings not to exceed 0.023 inch. Surfaces and exhaust gases are checked while the MSE is operated under optimal load conditions. Temperatures shall not exceed 550° F for exposed surfaces and 475° F for exhaust gases.
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How do I Inspect a Multiposition Small Engine Spark Arrester?

The first step for identifying the spark arrester is to check for the model number and/or manufacturer's identification or trademark. The words "Qualified" or "Approved" are not required, and do not indicate that the unit is in fact a qualified arrester.

  1. Once Identification is established, refer to the "Qualified List."
  2. If the arrester cannot be positively identified, use the following procedure.
    1. DETERMINE the make and model of the MSE the spark arrester is mounted on.
    2. CHECK the "Qualified List" for specific information on approved spark arresters for that particular MSE make and model.
    3. REVIEW the "Drawing Section" to match the arrester and verify the description.
  3. If not on the "Qualified " list, be sure to check any SAG update information you have received since the time of printing of your present SAG. The absence of an arrester from these lists indicates the arrester may not have been qualified.
  4. After the arrester has been identified, check the component requirements indicated on the "Qualified" list. Then turn to the Drawing Section and check the Spark Arrester illustration for an exact match on the configuration. The drawing must match the arrester you are inspecting.
  5. Tools needed for inspection are:
    1. Miscellaneous small hand tools for the operator, to remove or take apart spark arresters for inspection, including flat and cross tipped screwdrivers, needle nosed pliers and several types of chain saw combination tools available from local dealers.
    2. Flashlight
    3. 0.024-inch wire gauze to check screen size.
  6. Inspect the exhaust system for:
    1. Screen is in good condition with proper fit in it's holder and no openings larger than 0.023-inch.
    2. Condition and presence of all required parts assembled in their proper order.
    3. Verify configuration for necessary covers or shields.
    4. Required additional equipment such as handle bar, bumper spike(s), or chain brake are in place.
    5. Any modifications - none are allowed - to the exhaust system or engine.
  7. More detailed instructions are available in the NWCG video, "Spark Arresters and the Prevention of Wildland Fires".

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Inspection procedure for Chain Saws Manufactured Prior to 1978

Chain saws manufactured prior to June 30, 1978, are required to have all exhaust gasses pass through a screen with no opening larger than 0.023-inch. The screen must be heat and corrion resistant, and shall provide at least 100 hours of service life.

Many manufacturer's provide specific spark arrester screens for their pre-1978 brand and model of saws. On the other hand, many do not - but they meet the spark arrester requirement with a general purpose stainless steel screen (0.023-inch) which is allowed only on pre-1978 chain saws not listed in the SAG.

It is acceptable for chain saw shops and chain saw owners to size and install approved arrester screens only on saws manufactured before June 1978.

How do you determine a pre-1978 chain saw? Ask the operator or call the dealer with the serial number.
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Basic Definitions List:

Exhaust Particles - All internal combustion engines produce exhaust particles which are predominately carbon with contaminates. These particles originate from deposits formed on the internal surfaces of the engine or exhaust system and, depending on their exact origin, may be expelled at temperatures in excess of 3,000° F. Depending on the nature of the contaminates, these particles are capable of glowing or sometimes flaming combustion. When expelled through the exhaust system into the atmosphere, the combustion process may continue or even be accelerated during flight. Such particles, if larger than 0.023-inch in diameter and at temperatures of 1,200° F are capable of igniting cellulose materials upon contact.
 
Modification - Any modification or damage to any part of the system as it was presented to SDTDC for testing voids the qualifications of the spark arrester on the equipment. Modifications usually consist of removal of or damage to parts, change in exhaust outlets, replacing the fiberglass packing with steel wool, improper mounting, and bypasses.

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