1、 Errata NFPA 921 Guide for Fire and Explosion Investigations 2014 Edition Reference: 9.9.1.2 and 9.12.8.1 Errata No.: 921-14-2 The Committee on Fire Investigations notes the following error in the 2014 edition of NFPA 921, Guide for Fire and Explosion Investigations. 1. Revise 9.9.1.2 to read as fol
2、lows: 9.9.1.2 he The presence of sufficient energy for ignition does not assure ignition. Distribution of energy and heat loss factors need to be considered. For example, an electric blanket spread out on a bed can continuously dissipate 180 W safely. If that same blanket is wadded up, the heating w
3、ill be concentrated in a smaller space. Most of the heat will be held in by the outer layers of the blanket, which will lead to higher internal temperatures and possibly ignition. In contrast to the 180 W used by a typical electric blanket, just a few watts used by a small flashlight bulb will cause
4、 the filament to glow white hot, indicating temperatures in excess of 2204C (4000F). 2. Revise 9.12.8.1 to read as follows: 9.12.8.1 General. Lightning is another form of static electricity in which the charge builds up on and in clouds and on the earth below. Movement of water droplets, dust, and i
5、ce particles in the violent winds and updrafts of a thunderstorm build up a polarized electrostatic charge in the clouds. When sufficient charge builds up, a discharge occurs in the form of a lightning stroke strike between the charged cloud and objects of different potential. Lightning strokes stri
6、kes may occur between clouds or between clouds and the earth. In the latter, charges of opposite polarity are generated in the cloud, while the charge in the ground below the cloud is induced by the cloud charge. In effect, the result is a giant capacitor, and when the charge builds up sufficiently,
7、 a discharge occurs. Issue Date: July 24, 2014 (Note: Electronic products and pamphlet reprints may have this errata incorporated. For current information about the NFPA Codes and Standards, including this errata, please see www.nfpa.org/codelist) Copyright 2014 All Rights Reserved NATIONAL FIRE PROTECTION ASSOCIATION
