Unlike early diving, which relied exclusively on air pumped from the surface, these days scuba divers carry their own source of breathing gas (usually compressed air), which gives them a possibility to move freely compared to how it was previously when connected to and restricted by an air line. Both surface supplied and scuba diving allow divers to stay underwater significantly longer than with breath-holding techniques as used in snorkelling and free-diving. Diving equipment becomes more complicated and needs closer examination and monitoring before actually being used on dives. In 1995 Trident Diving Equipment, of Chatsworth, Calif., recalled approximately 500 screw-in DIN Tank Valve Caps. If tank pressure was 3000 psi or greater, the valve cap would not be properly inserted, and the air valve would be on, the valve caps could fracture and pop out of the air tank, causing injury.
