Not sure if this is the wording in the actual document:
Document Scope: 1.1.1 This guide applies to the design, location, installation, maintenance, and use of devices and systems that vent the combustion gases and pressures resulting from a deflagration within an enclosure so that structural and mechanical damage is minimized. A deflagration can result from the ignition of a flammable gas, mist, or combustible dust. 1.1.2 This guide should be used as a companion document to NFPA 69, Standard on Explosion Prevention Systems, which covers explosion prevention measures and can be used in place of, or in conjunction with, NFPA 68. The choice of the most effective and reliable means for explosion control should be based on an evaluation that includes the specific conditions of the hazard and the objectives of protection. Venting of deflagrations only minimizes the damage that results from combustion. 1.1.3 This guide does not apply to detonations, bulk autoignition of gases, or unconfined deflagrations, such as open-air or vapor cloud explosions. 1.1.4* This guide does not apply to devices that are designed to protect storage vessels against excess internal pressure due to external fire exposure or to exposure to other heat sources. 1.1.5 This guide does not apply to emergency vents for runaway exothermic reactions or self-decomposition reactions. 1.1.6 This guide does not apply to pressure relief devices on equipment such as oil-insulated transformers. It also does not apply to pressure relief valves on tanks, pressure vessels, or domestic (residential) appliances.
cdafd,
The new wording:
Origin and Development of NFPA 68
[I'm skipping the historical and coming up-to-date]
The 2007 edition represents a complete revision, including a change to standard. The new "Standard on Explosion Protection by Deflagration Venting" now provides mandatory requirements for the design, location, installation, maintenance, and use of devices and systems that vent combustion gases and pressures from deflagrations. The Committee incorporated a new chapter on performance-based design that enables users to present alternative design methods to satisfy the requirements for gas and mist mixtures, for dusts, and for hybrid mixtures. The committee also revised the generalized correlation for dusts on the basis of a review of additional experimental data. This review enabled the Committee to support revisions to the basic equation, along with changes to the equations for low-inertia vent closures, panel inertia, partial volume, initially elevated pressures, and vent ducts. The Committee also added a new chapter on inspection and maintenance.
I've been following work by the CSB and they've been pushing this change due to recent deaths over the past years resulting from dust explosions.
cdafd,
I've been hearing from other safety professionals that eventually all NFPA Standards/Guides are to become mandatory. True -or- not it appears that is happening a chapter at a time.
