Editing 3035: Trimix

{{comic
| number    = 3035
| date      = January 8, 2025
| title     = Trimix
| image     = trimix_2x.png
| imagesize = 436x259px
| noexpand  = true
| titletext = You don't want the nitrogen percentage to be too high or you run the risk of eutrophication.
}}

==Explanation==
{{incomplete|Created by a FLOATING TRIMIX SCUBA DIVER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
{{w|Trimix (breathing gas)|Trimix}} is a gas used in {{w|SCUBA}} tanks that consists of {{w|helium}}, {{w|oxygen}}, and {{w|nitrogen}}. Trimix comes in some standard ratios between the component gases, depending on the required diving depth, for example 21/35/44 (percentage oxygen/helium/nitrogen), 18/45/37 and 15/55/30 for increasing depth. Helium replaces a portion of the nitrogen to minimize nitrogen's narcotic effects at greater depths and to ease the effort required for breathing. This comic jokes that if the helium amount is too high, a diver will float away before reaching the water to start a dive, as a helium balloon will do if not securely tethered. 

The reason a helium balloon creates lift is that it can inflate. The balloon has a thin and expandable layer, weighing almost nothing, that allows the intrinsically less dense gas to take up space at not much more than atmospheric pressure. The total weight of the filled balloon is less than the total weight of the air it displaces, thus creating {{w|buoyancy}}. A SCUBA tank is made of metal, is heavy and cannot inflate,{{Citation needed}} which means it will never become lighter on air as you pump more of ''any'' kind of gas into it. (In fact, it will just get heavier, as an inflating helium balloon does, but without the over-compensating increase in volume.) Thus it will never be able to create any kind of lift, no matter the amount of helium or any other gas that is compressed inside of it, and neither could a typical SCUBA tank even attain lift by thoroughly emptying it to try to create a {{w|vacuum balloon}}.

More to the point, the rise into the air would be caused by Archimede's force, which is proportional to the weigh of the displaced volume. Air being ~ 1,3 g/L, it takes 1m3 to lift 1,3kg, and ~50m3 to lift a 65kg person. Such a volume represents a 2.3m radius sphere, which is obviously way bigger than the helium tank.

The real reason SCUBA divers need to be careful with the amount of helium is to not get too little oxygen or too much nitrogen.

The title text asserts that a trimix diver whose gas mix contains an excess of nitrogen runs "the risk of eutrophication". The term {{w|Eutrophication|eutrophication}} describes the process by which nutrients ("fertilizers") accumulate in an environment, typically a body of water, leading to consequences that are often unfortunate for inhabitants or users of that environment. The human body is an ecosystem, but one that is not typically subject to eutrophication due to its manner of acquiring and jettisoning nutrients. Moreover, the nitrogen in trimix is diatomic elemental nitrogen, not the {{w|Nitrogen_fixation|"fixed"}} nitrogen that serves as a component of eutrophication. The diver would not breathe "fixed" nitrogen unless nitrogen-fixing bacteria were somehow incorporated into the SCUBA gear, a complex feature of dubious utility.

[[Randall]] addressed the question "how much helium is needed to lift a human body" in a [https://what-if.xkcd.com/62/ What if?] article. Helium has also featured in comics [https://xkcd.com/2766/ 2766] and [https://xkcd.com/2972/ 2972].

==Transcript==
:[In a single frame five images of Cueball is shown as a kind of carton, with each image a later time in the process. The first image to the left shows Cueball standing by the shore of a body of water. He is wearing SCUBA gear, goggles, breathing tubes, SCUBA tanks with a small H logo on it on his back, and swimming flippers, which almost touch the water.]

:[In the next four images he has the same equipment on, but with changes. It should be seen as he is still at the edge of the water, but that is not drawn in the next four depictions of Cueball.]

:[In the second image  to the right of the first, Cueball's SCUBA tank is beginning to float upwards, so the end that is not teetered to Cueball move out and up, as shown with three small lines beneath the tank.]

:[In the third image the SCUBA tank is now floating above Cueball's head and the strings pull his arms a bit upwards. Cueball has turned his head looking up at the tank floating above and behind his head. Again three small lines beneath the tank indicates it is moving upwards.]

:[In the fourth image Cueball is now being lifted up, so his feet are now off the ground and he is tilting forward. The tank is now pointing it's bottom almost straight up and Cueball is looking down with his arms out the each side as the tank pulls him up. Two lines on either side of the tank indicate that it now wobbles above him as it lifts him up.]

:[In the fifth and last image the SCUBA tank is now pulling a dangling Cueball high above the ground, above his head's height in the first image. The tank is now turned so it points it's bottom to the left with lines on either side indicating wobbling motion. Cueball is floating as lying prone a bit bended on the middle as the tanks straps pulls him up. At this point he yells:]
:Cueball: ''Help!''

:[Caption below the panel:]
:Trimix SCUBA divers need to be careful not to let the helium percentage get too high.

{{comic discussion}}

[[Category:Comics featuring Cueball]]