Posted by Bill Johnson on August 11, 2001 at 01:42:33:

In Reply to: Nitrox aka EANx posted by CalAbDiver on August 09, 2001 at 13:04:27:

Some say that nitrox costs more than air. I say it doesn't.

Lets take a $100 boat trip including air (if you don't like $100, insert your own figure and redo the math). Following a Buehlmann ZHL-16 table, diving air to 95', next 85' and finally 75' for the maximum NDL times and 45 min SITs, nitrogen limits times to 17 min, next 10 min and finally 14 min, for a total of 41 min of dive time. $100 / 41 min = $2.44 per minute.

Using EAN36 for the same profile yields NDL times of 25 min (EAD 71' so 80' table), next 23 min (EAD 63' so 70' table) and finally 37 min (EAD 55' so 60' table), for a grand total of 85 minutes! That is over twice the dive time of air for the same amount of effort! If you paid $10 per fill for nitrox (I should be using the cost difference between air and nitrox, but I'll be generous to the nitrox cheapskates), then $130 / 85 min = $1.53 per minute. You could dive air with a computer to get more minutes, but then you are pushing yourself right up to limits of DCS. Not only is nitrox cheaper per minute, but there is more built in safety because of the EADs not maxing out the particular depth table.

While I can especially see the need for standardized gases in trimix, having two or three nitrox mixes does not ruin Mike's holistic argument he uses for EAN32. Lets say that EAN36 is 25% safer than air. 25% is just as easy as using 20% safety margin in brain deco calculations, so it doesn't seem to me that EAN32 is so special.

Nitrox is cheaper per minute and can add safety. Nitrox can even be more beneficial when calculated to the multi-day dive vacation cost. It can also allow you to get in another diver or two closer to take-off time, reducing the price per minute even more. Nitrox is not more expensive, it's cheaper!

Regards,

Bill