# Oxygen supply **URL:** \ **Category:** Factual Questions\ **Created:** [August 25, 2004, 2:49pm UTC](https://boards.straightdope.com/t/oxygen-supply/261446 "2004-08-25T14:49:31Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Moonwatcher](https://avatars.discourse-cdn.com/v4/letter/m/278dde/32.png) [@Moonwatcher](https://boards.straightdope.com/u/Moonwatcher)\ **Post date:** [August 25, 2004, 2:49pm UTC](https://boards.straightdope.com/t/oxygen-supply/261446/1 "2004-08-25T14:49:31Z")
Hi all, I use Oxygen for treatment of cluster headaches and after years of staring at my regulator I can’t get this stupid question out of my head: Why is the pressure in the tank measured in english units (Pounds per Square Inch) while the flow is measured in metric units (Liters Per Minute)? :dubious: ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 25, 2004, 3:21pm UTC](https://boards.straightdope.com/t/oxygen-supply/261446/2 "2004-08-25T15:21:15Z")
Ummm… because pressure and flow are two different things? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 25, 2004, 3:25pm UTC](https://boards.straightdope.com/t/oxygen-supply/261446/3 "2004-08-25T15:25:20Z")
Bad **Mangetout**! No cookie! OK, reading the question _properly_ now… I suspect it will be something like the pressure guage being manufactured (or specified) by an industrial gases company that uses non-metric measurements, and the flow meter being specified by a medical authority that uses metric. Sorry 'bout that - that’s the third time in twelve hours that I’ve posted a stupid hasty response (not to mention the stupid pensive ones, naturally) - time for a little break I think. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 25, 2004, 4:23pm UTC](https://boards.straightdope.com/t/oxygen-supply/261446/4 "2004-08-25T16:23:40Z")
The tank pressure gauge is usually part of the pressure regulator, which is a generic off-the-shelf device used in many fields. The same regulators are probably used in factories and machine shops, who all prefer English units. In Japan I had to deal with tank pressure gauges marked in kg/cm[sup]2[/sup]. ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [August 25, 2004, 7:12pm UTC](https://boards.straightdope.com/t/oxygen-supply/261446/5 "2004-08-25T19:12:50Z")
> [@Moonwatcher](#): > > Hi all, I use Oxygen for treatment of cluster headaches and after years of staring at my regulator I can’t get this stupid question out of my head: > Why is the pressure in the tank measured in english units (Pounds per Square Inch) while the flow is measured in metric units (Liters Per Minute)? > :dubious: One set of units for measurig pressure, manufacturer/supplier of tanks and gauges. Another set of units for measureing flow, in terms used by M.D.'s You should be able to find a web site that will convert the flow or the pressure into equivalent terms easier for you to understand. ---
**Author:** ![Moonwatcher](https://avatars.discourse-cdn.com/v4/letter/m/278dde/32.png) [@Moonwatcher](https://boards.straightdope.com/u/Moonwatcher)\ **Post date:** [August 25, 2004, 7:39pm UTC](https://boards.straightdope.com/t/oxygen-supply/261446/6 "2004-08-25T19:39:45Z")
Thanks for the responces. I don’t have any problems understanding PSI or LPM I just found it interesting that they used the two different measurment systems on the same device. My guess has been that folks are just used to using Pounds for measuring pressure and the Medical types like to use the metric Liters for flow and so if it aint broke don’t fix it. :smack: Thanks again though…more thoughts welcome