Packages or ammunition having valves for pressure-equalising

Official title: Packages or ammunition having valves for pressure-equalising; Packages or ammunition having plugs for pressure release, e.g. meltable {; Blow-out panels; Venting arrangements (ventilating arrangements on packages formed from foldable or erectable blanks B65D5/4295; packages with pressure-relief valves incorporated in a container wall B65D77/225)}

F42B39/20 (Packages or ammunition having valves for pressure-equalising) appears on 209 US grants and 95 published applications in this corpus.