Safety device
Safety device means a closure device such as a pressure relief valve, frangible disc, fusible plug, or any other type of device which functions exclusively to prevent physical damage or permanent deformation to a unit or its air emission control equipment by venting gases or vapors directly to the atmosphere during unsafe conditions resulting from an unplanned, accidental, or emergency event. For the purposes of this subpart, a safety device is not used for routine venting of gases or vapors from the vapor headspace underneath a cover such as during filling of the unit or to adjust the pressure in this vapor headspace in responses to normal daily diurnal ambient temperature fluctuations. A safety device is designed to remain in a closed position during normal operation and open only when the internal pressure, or another relevant parameter, exceeds the device threshold setting applicable to the air emission control equipment as determined by the owner or operator based on manufacturer recommendations, applicable regulations, fire protection and prevention codes, standard engineering codes and practices, or other requirements for the safe handling of flammable, combustible, explosive, reactive, or hazardous materials.
Source
40 CFR § 63.5610
Scoping language
For all affected sources complying with the batch process vent testing provisions in 63.490(c) and the operating limit provisions in 63.505(c), the terms used in this subpart and in subpart U of this part are defined in 63.482 and paragraph (g) of this section.