Follwing on from a Thread contected to spools I thought I'd post this here for all to read. This has been copied from a very good little site call bitz diving, link below They explain the use of the yellow DSMB better than i can. http://www.bitz.fsnet.co.uk/index.htm Yellow SMB What does it mean? To some a Yellow DSMB is used exactly as an Orange one, i.e. it is used to indicate the position and presence of divers. However in growing diving circles, particularly technical diving, it has become established as an emergency signal, to communicate to the surface that the diver below has a problem of some description. This could mean for example that he has simply lost his Orange DSMB or perhaps more importantly that he has insufficient gas to complete the planned dive without risking an early ascent to the surface and needs help. Shouldn't it be next to an Orange one if there is a problem? No! Some believe that a Yellow SMB on its own means that the diver has just lost his Orange one and no action is required. This is fundamentally flawed, after all, if a diver is in dire circumstances, he may not be able to inflate an Orange SMB, perhaps not being able to spare the time, effort or maybe even having lost it in what could be a highly stressful situation. You should always assume the worst case scenario unless you know to the contrary, even if there is a "loose" Orange SMB floating around with no divers below it. A Yellow buoy and an Orange buoy on the same line indicate a definite problem but you still have to take the same action if a Yellow buoy is on its own. You quite simply don't know any better. What if I own a Yellow SMB and no Orange one? Keep it and carry it, ideally with a spare reel or spool, but don't use it unless you have to. You may be grateful of it one day! Of course you will need to buy an Orange SMB as well. If I need to signal the surface do I do anything special? Assuming you have already deployed an Orange buoy then you simply clip your Yellow emergency SMB to the same line and inflate it. It would then float on the surface next to the Orange SMB. If you have the time and opportunity, it may be worth attaching a slate to the bottom with a message to indicate the nature of the problem. If you have not already deployed an Orange SMB, you would initially send up a Yellow SMB to indicate a problem (again with a message on a slate if you have the time and opportunity). You would then follow it with an Orange buoy on the same line if you can, but do not complicate an already difficult position to do this. It is best to be a little negatively buoyant in the water, hanging off the line. This will raise the buoy(s) into a vertical position and make it/them more obvious to the boat. It is also a lot easier to lower extra gas down a vertical line than one at an angle. If you simply lose your Orange DSMB, firstly use your buddy's SMB for the ascent, or if he doesn't have one, use your Yellow one but try to attach a message to the bottom to indicate that this isn't an emergency. This will avoid unnecessary action by the skipper and divers already on board! What do I do if I see a Yellow SMB? A lot will depend on the circumstances, but the following steps are probably a pretty good start. Remember that it may not be a friend's SMB…i.e. some unenlightened soul from a different club may be using it as a normal SMB. 1. Advise the skipper and the dive marshal (if already back on board) or any other experienced diver(s) and get the boat to approach the buoy. 2. Establish whether it belongs to a club member. It should have a name or identifying mark on it to indicate whom it is. 3. See if there is a message attached to the bottom indicating the problem, if any. 4. If no indication then assume the worst. The first step should if possible be to get extra gas down the line by slowly lowering a bottle along the SMB line on a length of rope, which is attached to a buoy capable of supporting its weight. Ideally it should be a decompression cylinder if one is available, but don't forget the regulator! Note: Decompression cylinders should be marked with the "Maximum Operating Depth", normally "6" or "21". Cylinders marked with a "6" should not be lowered below six metres, likewise cylinders marked with "21" should not be lowered below twenty-one metres, this is because of problems of Oxygen toxicity. If you have a choice, use a "21" metre cylinder in preference to a "6" metre, unless you can clearly see the divers close to the surface. 5. Either one or two "experienced" divers, dependent on their skills, the conditions and circumstances, should start to get ready to enter the water and proceed down the SMB line as soon as possible. But only after they have ensured that they have a sufficient gas supply and are not putting themselves at an unacceptable risk. What constitutes an unacceptable risk will depend on the individuals' skills and experience. If they are able to carry spare gas with them, then they should do so. Note: if there is a problem then it could be just below the surface at a decompression stop - possibly as little as 3 metres! So it may not be necessary to do a repetitive "deep" dive without an adequate surface interval. To restate never put yourself at an unacceptable risk! 6. The diver(s) find what the problem is, if possible solve it, and return to the surface to advise the boat of the nature of the problem so that any further action can be taken if necessary. If I want to buy a Yellow SMB, what sort should I get? Just go to Which Surface Marker Buoy? and it'll tell you everything you need to know Anything else? Remember that the SMB must be prominently marked with your name as a minimum and an indication of its purpose. E.g. "Howard" on one side and "Help!" on the other. Otherwise it may be difficult to tell if it is a friend in trouble or another club's diver who simply happens to own a Yellow SMB. SMB's can be marked with an indelible black pen, but be careful, some may run even when they shouldn't so perhaps test it on a small area first and then expose it to sea water. It should also be possible to clip it easily and quickly to a line by some means of attachment like a stainless steel clip.