Please note: All interim revisions for this edition available at time of your purchase will be included.Pressure Relief Valves for Sprinkler SystemsUL 1478AThese requirements cover pressure relief valves intended for use in sprinkler systems for fire protection service to relieve excessive pressures caused by thermal expansion, downstream of a pressure reducing valve or in valve trim.Requirements for installation of these valves are included in the Standard for Installation of Sprinkler Systems, NFPA 13.