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By the end of this topic, you should be able to answer these questions: 1 Why do you need a DSMB/lift bag on a technical dive? 2 What are suitable DSMBs/lift bags and how do you stow them prior to use? 3 What are the two types of signaling devices tec divers should always carry? Send it Up DSMBs (Delayed Surface Marker Buoys) and lift bags are an essential part of tec diving equipment, but how they are used varies widely in different locations. Although DSMBs and lift bags have differences, they are both used for the same overall purpose – to create an ascent line and signal to nearby boats that a diver is ascending. In some locations, divers nearly always plan to ascend using a DSMB/lift bag. In other locations, they are only used in an emergency, such as not being able to find or return to a fixed ascent line (anchor/mooring line, etc). Either way, carrying DSMBs/lift bags has become standard in many places for both recreational and technical diving. DSMB/lift bags provide an ascent reference, allow surface support personnel to track your position, and help you maintain your decompression stop in midwater. If you plan to ascend using your DSMB/lift bag, it's usual to carry a back up as well. As with other tec equipment, if you need one you also have a back up. It is recommended that you write your name on your lift bag/DSMB for surface support identification. DSMBs/lift bags should be easily visible at the surface and there are a variety of sizes and shapes, suitable for different conditions. The most common colors for DSMBs/lift bags are orange or yellow. Orange is the most easily visible in most locations. In areas with very bright light, black DSMBs are sometimes used because they stand out well against the glare. Check with your instructor or dive boat captain on the best options for the location. In some areas, divers carry different color DSMB/lift bags – a primary DSMB (or two, usually orange) plus one to signal for assistance (typically yellow) from surface support. Be sure to discuss and agree what action your surface support will take if you send up an emergency DSMB/lift bag. Different teams and areas have differing protocols regarding DSMB/lift bag colors and uses, your instructor will explain any local protocols, if you aren’t already aware of them. Photo credit Halcyon Dive Systems DSMBs are taller and more compact than lift bags and don’t usually have the same lift capacities. Lift bags were originally designed to lift items on recovery dives, while DSMBs were designed to mark diver’s position in the water and have become more popular than lift bags for this reason. Features Other features DSMBs/lift bags have include: Overpressure valves. These may be at the top or the bottom, but are usually at the top of a lift bag due to its original purpose, and lower on a DSMB to retain gas even if it leaks. One-way valves for filling. More common on DSMBs, these keep the buoy inflated even if it topples over at the surface. Inflation There are several methods for inflating DSMBs/lift bags. The design of the bag will guide your choices. DSMBs/lift bags with open bottoms or one way valves are usually filled from the bottom. Closed DSMBs have a valve that can be inflated orally and/or using a LPI hose. Most DSMBs/lift bags need the diver to provide some line resistance as they ascend, plus some downward pull after they reach the surface. This keeps types that can spill from doing so, and causes DSMBs to stand up and be visible. More on this later in the Techniques and Procedures section. Stowing DSMBs/lift bags must be stowed until they are needed. They are usually carried rolled/folded and need to be streamlined and secure, but easily accessible. Common locations are: Pockets/pouches on the waist band or suit thigh. Purposely designed pouches fitted to your backplate use the gap between your back and the plate for storage. These allow you to reach behind and pull them out. Bungee loops on the side or bottom of your backplate or harness. Divers using sidemount Signaling Devices As in recreational diving, tec divers should carry a visual and an audible signaling device on every dive. The most common are a whistle, either attached to your harness or clipped into a pocket and a DSMB/lift bag. It is common to also carry a small mirror that can be used to signal surface support. Tec divers walking into the water wearing back mounted doubles -credit Fourth Element EPIRBs (Emergency Position Indicating Radio Beacons) and PLBs (Personal Locator Beacons) are radio transmitters using GPS that are often carried by divers when sea diving in an area where a lost diver can't swim to shore. Diver versions are pressure rated, or carried in a housing specifically for diving. There are also satellite-based positioning systems available. When activated these units transmit a radio signal that can be picked up in the surrounding area up to about 50 kilometres/30 miles away. The range of signal depends on surface conditions and the length of the antenna. A lost diver at the surface is most likely to be found by their own dive boat or other small boats in the area, so this range targets those vessels. Some units also have Automatic Identification System (AIS). This is the same system ships use to see each other and avoid collisions. Systems with AIS can be paired with your vessel and have a non-emergency locator so that your boat (and any others in range) can see where you are.