roofing surface (shingle, thatch, or bitumen-felt) or falling onto combustible material on the ground. Such a spark arrester typically consists of a double layer of metal mesh, which catches the ember and allows the flue gas to escape. Large power station boilers are commonly fitted with electrostatic precipitators. Electrical equipment Types Centrifugal Centrifugal type spark arresters employ stationary vanes, baffles, or other devices to trap large particles by centrifugal force. These spark arresters are typically found on heavy agricultural and construction equipment (tractors, combines, bulldozers, etc.), but some have been developed for motorcycles and other all-terrain vehicles. Screen Screen type spark arresters use a physical mesh to prevent large particles from leaving the exhaust system. This is the simplest and most common type of spark arrester. Screen type devices are used on most motorcycles, ATVs, and small engines. Electrostatic precipitator Regulatory requirements United States Laws governing spark arrester use in the United States depend on the jurisdiction. Internal combustion engines operating on USDA Forest Service and most other federally managed lands must meet the requirements of the Code of Federal Regulations 36 CFR 261.52. This mandate requires the operator to have a certified and properly maintained spark arrester installed at all times. Many state and local land management agencies defer to the federal requirement. Exemptions exist for automobiles legally registered with their state's department of motor vehicles. During periods of extreme fire danger, land managers may prevent the use of all motorized equipment, even if a properly functioning spark arrester is installed. Spark arrester inspections are performed by trained agency law enforcement or fire prevention personnel. They may occur on an individual basis, or as part of an inspection checkpoint during busy recreation weekends. Operators caught using unqualified or modified devices could be cited. Penalties for violating spark arrester laws depend on the issuing agency. If it is determined a noncompliant vehicle was responsible for starting a fire, the operator could be held liable in civil or even criminal court. Certification testing of spark arresters is performed by the USDA Forest Service Technology and Development Center in San Dimas, CA. The technical requirements are outlined in Forest Service Specification FS5100-1. All spark arresters meeting the requirements of 36 CFR 261.52 must be certified and listed in the USDA Forest Service Spark Arrester Guide. This guide is a comprehensive directory of all qualified products available in the United States, and is