Spark Arrester Qualification

Spark Arrester FAQs

1. What are the legal requirements governing the use of spark arresters?

It depends on the jurisdiction where the equipment is being used. Spark arrester regulations in the US appear to have originated with the US Forest Service (USFS). The most commonly cited law is US Code 36 CFR 261.52(j), which states that "When provided by an order...operating or using any internal or external combustion engine without a spark arresting device that is properly installed, maintained, and in effective working order in accordance with U.S. Forest Service Standard 5100-1" is prohibited.

We'll get to what USFS Standard 5100-1 is in a minute, but first, what does "When provided by an order" mean? This refers to specific fire "orders" (restrictions) that are controlled by each Forest Supervisor within the National Forest System, the intent being to limit hazardous activities during times of high fire danger. However, as of 2020, there are standing, multi-year fire restrictions in effect that specifically cite 36 CFR 261.52(j) for all Forests in California, and many others throughout the US, including (but not limited to) those in Arizona, New Mexico, Oklahoma, Texas, Colorado, Kansas, Nebraska, Wyoming, South Dakota, Idaho, Montana, North Dakota, and Washington, meaning spark arresters are required there 365 days per year. During periods of critical fire danger, the USFS may ban all use of motorized equipment, even if it has a spark arrester installed.

Many other Federal land management agencies defer to the USFS regulation (for example, the Department of Interior, which governs the National Park Service, Bureau of Land Management, Fish and Wildlife Service, and Bureau of Indian Affairs) . State and local regulations may vary, but many defer to the Federal requirements and/or have their own individual restrictions. For instance, California Public Resources Code 4442 refers to the Forest Service standard, but also allows for spark arresters that are not qualified by the USFS provided they meet the same technical requirements. Even some foreign countries, including Australia, reference the USFS standard.

Because of the broad adoption of spark arrester laws, many manufacturers of off-highway vehicles and outdoor power equipment provide spark arresters as an OEM component. Aftermarket products are also available, especially for all-terrain vehicles (ATVs). Since a single ATV trail may pass through local, state and federal land, most riders find it's worth the minimal cost and effort to install a spark arrester, especially when the alternative is the risk of recieving a costly citation or starting a fire. Haavard Krislok of BoostATV has a great article about spark arresters written from an ATV user's perspective.

2. Who regulates spark arresters? Are there exemptions?

As of 2020, the US Forest Service appears to be the only agency with Federal regulatory authority for spark arresters in the United States. It publishes FS5100-1 ("Standard for Spark Arresters for Internal Combustion Engines") which defines spark arrester performance requirements. The USFS also oversees certification of products to the standard in accordance with the Society of Automotive Engineers (SAE) test standards J335 (small engines in handheld products), J342 (locomotives and stationary power plants), and J350 ("general purpose", i.e. all other applications). Equipment manufacturers must submit spark arresters to the USFS San Dimas Technology and Development Center for testing. If the product meets the requirements, it is placed in the Forest Service's Spark Arester Guide (link warning: this is large PDF), a listing of all qualified spark arresters. Law enforcement on federal (and many state and local) lands are trained and authorized to enforce spark arrester laws.

Some equipment is exempt from spark arrester requirements, but again, it depends on the jurisdiction. For example, vehicles operating on public roads on Federal lands are generally not required to have spark arresters if they meet the applicable motor vehicle code. FS5100-1 also states that vehicles with turbochargers and/or Diesel Particulate Filters, (if they meet certain specific requirements) are exempt from needing a purpose-built spark arrester.

3. Do modern engines really still produce "sparks"?

The term "spark arrester" has become somewhat of a misnomer, as it is uncommon (but not impossible) to see visible sparks or embers eminating from modern engines . Nearly all internal combustion engines produced today use some form of computer-controlled ignition in order to meet efficiency and emissions requirements, which has greatly improved their performance. However, there are still potential sources of hot debris inside the engine and exhaust system that could be ejected and may start a fire. Older and poorly-tuned engines can develop carbon deposits which may eventually break free and exit through the exhaust system. Exhaust pipes can corrode and crumble. Catalytic converters, now common even on small engines, can also fail, ejecting hot pieces of the catalyst matrix. Fire investigators have commonly cited catalytic converter failures as a cause of roadside fires (1, 2, 3, 4, 5), including the devestating Freeway Complex Fire in Southern California in 2008 (though, interestingly, the spark arrester laws did not impact any of these cases since they involved motor vehicles operating on public highways).

Even though we expect modern engines to present less fire risk than older ones, given the scope and public visibility of the global wildland fire problem, it is unlikely that regulatory authorities will relax or eliminate existing fire protection standards any time soon.

Interestingly, emissions requirements, although beneficial to air quality and public health, present new challenges in terms of fire risk. Diesel particulate filters (DPFs) and Selective Catalytic Reduction (SCR) systems can become very hot during operation and may ignite dry vegetation that comes in contact with their hot surfaces.

4. How do spark arresters work?

There are two general types of spark arresters - the "screen type" and the "trap type". Screen type spark arresters are the simplest and most common. They use a metal mesh (hole size <0.023 inches) that fits into the exhaust system (generally an endcap on the muffler) to physically prevent any debris larger than the holes from escaping. Screen type spark arresters are used on small (chainsaws, weed trimmers, generators) and medium (ATVs)-sized engines. They require a method for users to remove and clean the screen (an exception is consumer-grade outdoor power equipment with sealed mufflers whose short design life precludes the need to remove the screen for cleaning). For handheld outdoor power equipment , FS5100-1 also prescribes maximum exhaust surface temperatures since these devices have the potential to be set down in dry vegetation while still hot.

Trap type spark arresters use vanes and baffles inside of the exhaust system (usually part of the muffler) to trap debris using centrifugal force. Unlike screen types, which can easily be examined using visual inspection and pin gages, trap type spark arresters must be tested using a large flow chamber (test details are defined in SAE J350). The test involves flowing air through the spark arrester at realistic exhaust flow rates. Carbon particles are injected into the airflow, and the spark arrester must capture at least 80% of them (by mass).

5. I'm an equipment manufacturer. How do I get my spark arrester qualified?

The USFS San Dimas Technology and Development Center performs all qualification testing of spark arresters. After paying a fee, a test sample must be submitted for evaluation by the agency. If the sample fails, it is returned to the manufacturer and will have to be resubmitted, causing costly delays.

Becker Support Services experts have direct experience with spark arrester qualification and can help guide you through the process. We will evaluate your product in accordance with the appropriate SAE test standards and handle the entire submission and qualfiication process on your behalf. Contact us for more information.