Mailing List Archive Mailing List Archive
Prem, the short answer is that what you are considering is a VERY bad idea. Gas switches on FFM's need to be avoided, and relying on a quick disconnect for your life support in this case is even worse. The following text is copied from a post I made to the Quest list a while ago regarding the use of FFMs: > Robert, first off, I hope you understand all of the risks that are associated with using these - increased dead gas space, increased gas consumption, freeflow (and freeze) risk, the constraint of mask and reg, and of course, the gas sharing CF. If you can get away without using the FFM, do so. If you genuinely require the mask for safety reasons (swiftwater, black water, minor contaminants, tox risk or necessary hardwire comms) then use it as follows: Rig the FFM, which feeds from the right as with any other second stage (AGA Interspiro MKII is not standard this way) to the backup reg hose. You may need to use a hose length slightly longer than standard to ensure a complete range of motion without tugging on the mask. The long hose is clipped off (as you would in any other situation) to the right chest D-ring, available for immediate deployment. The backup mask (standard half-mask) is kept in the thigh pocket as usual. If you can see each other, comms are not necessary, and hence the FFM is not necessary unless you need it for one of the other reasons listed above. If you must have the comm link, forget the through-water nonsense and use a proper hardwire. When you need comms, you need them to be clear, consistent and reliable - DIR, insofar as that's possible with the FFM. As for the masks themselves - as mentioned above, the AGA feeds from the wrong side without modification. The EXO is a bit too bouyant and will tug at your face. You can add a trim weight to it, but then it feels massive. If you can swing it, the DSI bandmasks are the way to go, but failing that the ScubaPro is a pretty good unit for the price. I use this in swiftwater, and the lower profile compared to the other masks is better for keeping it from getting ripped off your face. I also have an AGA, which I modified to feed from the correct side, but I hardly ever use it. I can't stress enough that you really need to think carefully about the risks to determine if the dive warrants a FFM. Usually the answer is no. One other thing - I use the ScubaPro (when necessary only) because it has oral/nasal separation, which reduces the total dead gas volume of the mask, but it also reduces the clarity of voice comms. If you are selecting a FFM based on the need for comms as a primary consideration, you probably want one that keeps your mouth and nose in the same space (oral/nasal cup) to keep your voice as intelligible as possible over the comm line. -Sean < PS: Prem, if you are serious about learning more about diving, particularly with regard to dive safety or diving beyond recreational limits, you would do well to surround yourself with more appropriate influences than Dr. Black. One need merely refer to the archives of this list for evidence of MJB's continual disregard for fairly simple safety considerations, and his complete disdain for logical reasoning in the explanation of these practices. Dive safe. -Sean Quoting Prem <prem@cs*.wi*.ed*>: > Hello; > > My name is Prem Mansukhani. This is my first posting to the group, so I > apologize for any breaches of etiquette common to this group. I am a > graduate student at the University of Wisconsin at Madison, and am active > with the Hoofers diving club, and friends with Mike Black, Matt "skippy" > Bauer, and Matt Schultz. I have been diving for four years with dives > totaling between 150 and 200. Most of my dives have been Midwest inland > lake, and Great lake dives. I also dive master for the club's introductory > classes. Needless to say, I consider myself to be a complete newbie when > it comes to technical diving. My major interest is ship wreck diving. To > date I have made about 20 non penetration dives on wrecks like the willie > off milwaukee, the frank off door county, and the smith moore off munising. > > Now with the introduction out of the way, on to my question. I recently > purchased an AGA Interspiro FFM. I like it, but I am somewhat concerned > using it at depth because if I would ever have to use my pony, I would have > to doff the mask. I therefore was thinking about putting some kind of > quick connect between the mask and the first stage, so I could change to my > pony without taking off my mask. I have found some medical quick connects > meant for use with oxygen/medical air regulators (between the first and > second stage) and think they would work, but I don't know there full > working envelope. Has anyone tried this before? Would the standard low > pressure quick connect work, (I don't think so but as I said I am a > newbie)? Is this just a bad Idea? Any suggestions would be appreciated. > > prem > > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]