In many instances, emergency venting is provided through pressure relieving devices such as weighted cover style emergency vents, loose manhole covers, rupture or burst disks, remote-actuated relief devices, or other pressure relieving equipment that may be used in place of pressure relieving tank designs. Although less recognized, in legacy installations the weak roof-to-shell seam construction technique may be used as emergency venting. Remember that in double-walled tanks, equal capacity venting must be provided for both the primary tank and the secondary containment vessel.