Vacuum relief is automatic on vertically-installed vents and manual on horizontally-installed vents.
Justrite Drum Vent for Petroleum Based Applications, Polyethylene, Vertical, Steel Flame Arrester, 2" Bung, Steel/Brass/Polyethylene, 08006 | Justrite Drum Vent for Petroleum Based Applications, Polyethylene, Vertical, Steel Flame Arrester, 2" Bung, Steel/Brass/Polyethylene, 08006 08211 includes a 9-in(229-mm) wide polyethylene funnel to facilitate solvent waste disposal and reduce spillage. All safety drum vents automatically relieve pressure between 3 and 8 psi (30 to 55kPa) and include a flame arrester to absorb and safely dissipate heat.