FIRE SAFETY REQUIREMENTS FOR WIRES AND CABLES

摘要

Wires and cables are among the products which are most often regulated for their fire safety. A key reason is that they are often found in concealed spaces, including (particularly in North America) in plenums and other air-handling spaces. In the US, the federal government has not issued fire safety requirements for wires and cables in buildings. However, most fire safety requirements for wires and cables in buildings are in the National Electrical Code (NEC, NFPA 70), widely adopted throughout the country. NEC fire safety requirements for wires and cables address various categories: (1) power cables, (2) wires and cables associated with power-limited circuits (including signaling cables, fire alarm systems and optical fiber cables) and all types of communications cables and circuits, (3) wires and cables associated with information technology equipment (4) fire resistive cables. The more severe fire safety requirements correspond to the first two categories, which use cable tray fire tests oriented horizontally (for plenum cables, measuring flame spread and smoke, see figure below) or vertically (for riser and tray cables, measuring primarily flame spread). In the US both major organizations issuing codes, including building codes, call upon the NEC (NFPA 70) for requirements on electrical safety (including fire safety). Interestingly, regarding fire safety regulation of products (including wires and cables) in plenums, the NEC is subservient to a consensus standard known as NFPA 90A (Standard for the Installation of Air-Conditioning and Ventilating Systems). Specific US fire safety requirements have been issued by the FAA for aircraft and by the USCG for vessels that do not sail in international waters. IMO regulations apply to vessels sailing in international waters, including some fire tests for wires and cables. US federal agencies have issued no wire and cable fire safety rules for land surface or underground transportation. Fire safety of intercity and interstate passenger trains is regulated by the FRA, which do not include wires and cables. Highway passenger vehicles (including automobiles) are regulated by NHTSA and mass transportation (buses and underground trains) is regulated by FTA, but wires and cables are not covered by either. However. NFPA 130, a widely-adopted consensus standard, regulates regulate the fire safety of wires and cables in trains and underground systems. In the European Union, the EC regulates the harmonization of legislative, regulatory and administrative provisions for all member states. The EC issued the Construction Products Regulation, which includes "Safety in case of fire" as one of the 7 basic requirements. The fire classification system for construction products is EN 13501, which contains standards with the information for requirements for many building products, including wires and cables, covered in EN 13501-6. Tests and classification systems apply to all countries but each determines requirements for any specific application, via interpretative documents. Categories range from A (best) to F (no performance determined) and measurements are made of flame spread and heat release as well as optional additional measurements of smoke emission and acidity. In the EU. the fire safety of all materials in trains (including wires and cables) is covered in EN 45545-2 (Railway applications - Fire protection on railway vehicles - Part 2: Requirements for fire behavior of materials and components) while the fire safety requirements of the FAA apply to all aircraft worldwide. This work discusses the major fire tests used to regulate fire safety of wires and cables in the US and EU.