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This is a multi-part message in MIME format. ------=_NextPart_000_002B_01BFDCA3.999DD160 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Have the WKPP or, anyone else for that matter, developed an acceptable = or maximum delta in PO2 during a gas switch. As I understand it, many = ox-tox incidents occur because of the momentary "spike" in PO2. Scott = Hunsaker has addressed this to some degree but has not mentioned any = numbers regarding an acceptable delta in PO2 or the relation to time and = this sudden elivation in PO2. ----- Original Message -----=20 From: David Chamberlin=20 To: Trey=20 Cc: Tech Diver=20 Sent: Sunday, June 11, 2000 8:36 PM Subject: Re: Deco gas selection Trey wrote: >=20 > What the fuck are you talking about? I never use trimix above 21% = Oxygen > below 120 feet. It is stupid. That's what I would've thought, and that's why I asked the question.=20 The person who responded in private e-mail was someone I thought was very knowledgeable about DIR SOP, so I wanted to go straight to the = DIR source and find out 1) if that was in fact the recommended gas and 2) Why that would be selected. =20 > The use of ONE gas for deco imples 50% - we > have been over this, Sorry. I tried doing a search for this topic and the only responses I came up with were the ones I posted earlier which didn't really cover the "why's" of the choice of 50/50. So I was attempting to get more information and clarification. As I said in my earlier post, I'm not doubting what you are saying is correct - I just want to understand it better. =20 > Everyone else has been over > this. Wake up. I'm sorry. As I said before, I tried to find earlier posts on this = and I only got some scattershot and very brief messages, which is why I posted the question. So let me try an abbreviated form of my = question.=20 I'm going to state what I think the rationale is for using 50/50 for a one gas dive to depths <=3D50m with times <=3D30 min, in spite of what = seems to be contradictory information from the Baker's Dozen. 1) The 50/50 let's you open your oxygen window earlier and thus you clear out most of your deco earlier, so you don't have to do so much "damage repair" at the shallower stops. 2) The benefit of clearing out your deco earlier outweighs the fact = that deco on 50/50 will not be as beneficial at the shallower stops. And since you cleared out most of your deco early, you don't need to be as efficient at the shallower stops. 3) The Baker's Dozen is comparing 80/20 at a depth of 30FSW, to 100% = at a depth of 20FSW. The difference in depth between these two is not significant enough to apply the reasoning of 1) and 2) to 80/20, and thus 80/20 pretty much has all the downsides and none of the upsides. And finally, I'd like to reiterate one of my questions in my previous post. You had said, "Most of my ocean dives are one gas dives - I do not generally see the need for the oxygen at all on a short hop first dive, and prefer not to take the beating of using it for not reason." What is the beating you are referring to? Have you found that these types of short exposures to high (1.6) PO2s actually have longer-term effects? =20 Thanks, Dave -- 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'. ------=_NextPart_000_002B_01BFDCA3.999DD160 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content=3D"text/html; charset=3Diso-8859-1" = http-equiv=3DContent-Type> <META content=3D"MSHTML 5.00.2614.3500" name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=3D#ffffff> <DIV><FONT face=3DArial size=3D2>Have the WKPP or, anyone else for that = matter,=20 developed an acceptable or maximum delta in PO2 during a gas switch. As = I=20 understand it, many ox-tox incidents occur because of the momentary = "spike" in=20 PO2. Scott Hunsaker has addressed this to some degree but has not = mentioned any=20 numbers regarding an acceptable delta in PO2 or the relation to = time and=20 this sudden elivation in PO2.</FONT></DIV> <BLOCKQUOTE=20 style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: = 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV> <DIV=20 style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B>=20 <A href=3D"mailto:dwc@na*.co*" title=3Ddwc@na*.co*>David = Chamberlin</A>=20 </DIV> <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A = href=3D"mailto:trey@ne*.co*"=20 title=3Dtrey@ne*.co*>Trey</A> </DIV> <DIV style=3D"FONT: 10pt arial"><B>Cc:</B> <A=20 href=3D"mailto:techdiver@aquanaut.com" = title=3Dtechdiver@aquanaut.com>Tech=20 Diver</A> </DIV> <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Sunday, June 11, 2000 = 8:36 PM</DIV> <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: Deco gas = selection</DIV> <DIV><BR></DIV>Trey wrote:<BR>> <BR>> What the fuck are you = talking=20 about? I never use trimix above 21% Oxygen<BR>> below 120 feet. It = is=20 stupid.<BR><BR>That's what I would've thought, and that's why I asked = the=20 question. <BR>The person who responded in private e-mail was someone I = thought=20 was<BR>very knowledgeable about DIR SOP, so I wanted to go straight to = the=20 DIR<BR>source and find out 1) if that was in fact the recommended gas = and=20 2)<BR>Why that would be selected. <BR><BR>> The use of ONE = gas for=20 deco imples 50% - we<BR>> have been over this,<BR><BR>Sorry. = I tried=20 doing a search for this topic and the only responses I<BR>came up with = were=20 the ones I posted earlier which didn't really cover<BR>the "why's" of = the=20 choice of 50/50. So I was attempting to get more<BR>information = and=20 clarification. As I said in my earlier post, I'm not<BR>doubting = what=20 you are saying is correct - I just want to understand = it<BR>better. =20 <BR><BR>> Everyone else has been over<BR>> this. Wake = up.<BR><BR>I'm=20 sorry. As I said before, I tried to find earlier posts on this = and<BR>I=20 only got some scattershot and very brief messages, which is why = I<BR>posted=20 the question. So let me try an abbreviated form of my question. = <BR>I'm=20 going to state what I think the rationale is for using 50/50 for = a<BR>one gas=20 dive to depths <=3D50m with times <=3D30 min, in spite of what = seems<BR>to=20 be contradictory information from the Baker's Dozen.<BR><BR>1) The = 50/50 let's=20 you open your oxygen window earlier and thus you<BR>clear out most of = your=20 deco earlier, so you don't have to do so much<BR>"damage repair" at = the=20 shallower stops.<BR><BR>2) The benefit of clearing out your deco = earlier=20 outweighs the fact that<BR>deco on 50/50 will not be as beneficial at = the=20 shallower stops. And<BR>since you cleared out most of your deco = early,=20 you don't need to be as<BR>efficient at the shallower stops.<BR><BR>3) = The=20 Baker's Dozen is comparing 80/20 at a depth of 30FSW, to 100% at<BR>a = depth of=20 20FSW. The difference in depth between these two is not<BR>significant = enough=20 to apply the reasoning of 1) and 2) to 80/20, and<BR>thus 80/20 pretty = much=20 has all the downsides and none of the upsides.<BR><BR>And finally, I'd = like to=20 reiterate one of my questions in my previous<BR>post. You had = said,=20 "Most of my ocean dives are one gas dives - I do<BR>not generally see = the need=20 for the oxygen at all on a short hop first<BR>dive, and prefer not to = take=20 the<BR>beating of using it for not reason." What is the beating = you=20 are<BR>referring to? Have you found that these types of short = exposures=20 to<BR>high (1.6) PO2s actually have longer-term effects? =20 <BR><BR>Thanks,<BR>Dave<BR>--<BR>Send mail for the `techdiver' mailing = list to=20 `<A = href=3D"mailto:techdiver@aquanaut.com'">techdiver@aquanaut.com'</A>.<BR>S= end=20 subscribe/unsubscribe requests to `<A=20 = href=3D"mailto:techdiver-request@aquanaut.com'">techdiver-request@aquanau= t.com'</A>.<BR>--<BR>Send=20 mail for the `techdiver' mailing list to `<A=20 = href=3D"mailto:techdiver@aquanaut.com'">techdiver@aquanaut.com'</A>.<BR>S= end=20 subscribe/unsubscribe requests to `<A=20 = href=3D"mailto:techdiver-request@aquanaut.com'">techdiver-request@aquanau= t.com'</A>.<BR></BLOCKQUOTE></BODY></HTML> ------=_NextPart_000_002B_01BFDCA3.999DD160-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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