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The case for using Gas Blocks by public safety divers

Discussion in 'Public Safety Divers' started by rkinder, Aug 25, 2016.

  1. Jared0425

    Jared0425 Public Safety Diver

    # of Dives: 500 - 999
    Location: Detroit, Michigan
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    In public safety diving, you should not have any gas but air. Our team has the lgs block that we use on our gear and it beats ripping the mask off in 35° water.
     
  2. rkinder

    rkinder Public Safety Diver

    # of Dives: 5,000 - ∞
    Location: Seneca, SC
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    Dear Jared0425,

    The LGS block, you mention is the RSV-1 manufactured by Sartek Ind. It is a design that has been around for a long time. There are many folks that like it. Good points is ease of use and light weight. Bad points I have always been concerned about the plastic and the mounting location along with the slight possibility of it sticking between settings in that it is a push side to side configuration, along with SCUBA type quick connects, including the primary gas supply.

    That being said it is a unit with a long history.

    Take care
     
  3. fraserpenny

    fraserpenny Angel Fish

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    Hi, I’m looking at possibly going to this type of setup for personal use in mostly cold water.
    Can anyone provide pictures of their setup?
     
  4. 73diver

    73diver Solo Diver

    # of Dives: 200 - 499
    Location: Milwaukee, Wisconsin
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    The Apeks AP0281 switch block manual is available online as a *.pdf and has pictures and instructions for use.
     
  5. Akimbo

    Akimbo Lift to Freedom Volunteer Staff Member ScubaBoard Supporter

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    As mentioned, diver mounted and controlled switch blocks are for using the same gas on all ports. Aside from diver operator errors, there is a real possibility of internal valve leakage contaminating the mix.

    This problem is managed in the better-designed commercial diving gas manifolds with the vent-to-atmosphere method. They are typically installed in gas shacks and saturation diving control consoles to supply diver or bell umbilicals. A typical manifold might have air, pure oxygen, and 2-4 HeO2 mixes. Each gas has a manual control valve, then a T-connection with a small valve that vents to atmosphere, and a check valve before entering the manifold that feeds the umbilical. The manifolds usually also have a small valve for an Oxygen analyzer.

    Contaminating (changing the mix) is most critical for the gas feeding the diver but internal leaks past valve seats can also contaminate gas banks. The vent between the check and stop valve make it impossible when operated properly.
     
    northernone likes this.
  6. fraserpenny

    fraserpenny Angel Fish

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    I checked out the Apeks and found KM PDF’s.. good source of info but, I still have some questions.

    1. Does anyone keep an octo on their primary air source? Is there any need?

    2. Just to imagine what the pony bottle would look like as there wasn’t much reference to it in the PDF’s.
    -a first stage with
    Connector hose to the switch block
    Over pressure relief valve
    An SPG
    Drysuit hose??
    Octo??

    Thanks for the help, this is all pretty new stuff to me
     
  7. rkinder

    rkinder Public Safety Diver

    # of Dives: 5,000 - ∞
    Location: Seneca, SC
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    In answer to your question I prefer to mount a 30 cuf bottle on the left side of my primary. A second stage is plumbed into the first stage on the pony as well as a hose to the EGS valve. You do not need an Over Pressure Valve when a second stage is attached to your first stage on the bail out bottle. Generally I use a 36 inch hose and route out the right side of the rig next to the primary second stage. If you mount a Kirby style block on the right side of your chest using the chest strap having it positioned below the nipple line the supply lines should feed under your right arm you can run the supply to your FFM up the front strap or zip tie the two supply lines, and regulator feed hose so that it comes over the right shoulder. Hope this is enough of a word description to get you in the right direction.
     
  8. fraserpenny

    fraserpenny Angel Fish

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    Yes it definitely gets me going in the right direction, I appreciate the detailed description as I’m fairly isolated from local dive shops and I don’t know anyone that dives ffm. So I figured this was the best place to find true tested information.
    Once again thanks for the help. If by chance anyone someone does have pictures that they are willing to share, that would be great too.
     
    Jordan Trotter likes this.
  9. BladesRobinson

    BladesRobinson ScubaBoard Supporter ScubaBoard Supporter

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    I realize this is a late post but I will add my two cents in an effort to promote a "point/counter point" dialog in an effort to further education.

    Know in advance that RKINDER and I are longtime friends and to Robert's credit, he has a lot of experience. I won't stoop to a level of who is right/wrong but I think it's worth a rebuttal and offer my OPINION...

    From coast to coast, there are many public safety dive teams with various levels of training, experience, budgets and skill sets. We all know that one of the tremendous benefits of full face masks to allow underwater two way communications and to assist in limiting contaminated water exposure. In recent years, there have been "near miss" incidents that have occurred because public safety divers have used air switch blocks in the wrong configuration as opposed to diving with a completely separate, redundant air system. While we can acknowledge that these "air blocks" were used improperly, we must also acknowledge that some of these accidents happened to well trained divers on well trained dive teams. Accidents do happen and I am of the opinion that when the "safety systems" (aka "air blocks") are a common denominator in the accident, we as a community need to re-examine these systems. We had some discussion on one of these incidents in an earlier era. See: FOR PSD's - A rare glimpse into Post Traumatic Stress Disorder

    There are near miss cases I also recall in Illinois and North Carolina and a PSD fatality in South Dakota (Thumma 7-13-14) where switch blocks are reported in the wrong position or in the case of the PSD fatality, assumed by many to be a root cause to the diver's death (diver dies at 15-20' depth with 19 cf pony bottle at 35 psi and primary tank at 2200 upon recovery).

    I am a proponent of the Hogarthian/KISS/Keep It Simple theory. Scuba systems that utilize simple configurations work well on a huge majority of dives. Adding more "stuff" does not necessarily make a diver safer and is the reason why Bill Hogarth preached a minimalist and streamlined approach to cave diving. Additionally, I am on record stating "If one believes that doffing the full face mask in an out of air emergency exposes a PSD to a huge contamination risk, then the team should be using helmets mated to dry suits or hire a commercial dive team to conduct the operation." The PSD Line of Duty Death database maintained by the IADRS shows that well trained divers and well trained public safety dive teams do not accidently have "out of air" emergencies. In conclusion, my strong belief is out of air emergencies should never happen when a diver monitors his SPG, the tender monitors the diver's air supply/consumption, and the back up diver, the 90% diver, the safety officer and the dive team leader are all monitoring the diver's primary air supply! There are five backup to the back up! So when an emergency does happen, as it did with Swope (Boise, ID), Thumma (Sioux Falls, SD) and others, they need the pony bottle to work and the pony bottles work 100% of the time when they are NOT plumbed to switch blocks!

    My opinion....
     
  10. rkinder

    rkinder Public Safety Diver

    # of Dives: 5,000 - ∞
    Location: Seneca, SC
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    Blades I will not disagree that commercial divers are much better prepared to deal with contaminated water and recovery of heavier items, or working in current. I have a lot of respect For Bill and his development of a simple stream lined approach to Technical Diving, more is not always better. The main problem I see with gas blocks being in the wrong position is a failure to train, failure to use check lists, failure for PSD's to work as a team. If I am in a full face mask bailing out to a second stage needs to be reflexive, just as dropping a weight belt or weight drop should also be reflexive. Yet each year somewhere around 75 percent of dead divers are recovered with their weights in place. My point is this, a diver well trained in using their equipment will only find it to be an inconvenience should they be equipped with a pony bottle with regulator or a Gas Block.

    Unfortunately, most divers do not continue to train in emergency procedures, removing a mask, locating your safety second stage and then your backup mask when a diver is already panicked this becomes a daunting task. With a properly configured gas blocks and religious pre dive safety checks a loss of GAS on the primary becomes turn on the valve, and abort the dive. There is no thermal shock when removing the FFM, no loss of vision due to loss of mask, no fumbling for the octo, no loss of communications if running communications. The case is clear as to which is easier and safer to deploy.

    But no matter what system a diver or team uses, there is a responsibility to train and become proficient with our equipment. There is a responsibility to properly check equipment prior to divers entering the water. I applaud your efforts to promote safety in our profession, and it is ok for us to view this from different angles. Based on our prior conversations I know that we both believe a diver that continually trains for the unexpected will find most to be inconveniences rather than emergencies. Take care and safe diving.
     

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