A comment below Was “I have the farts, again” broadcast from the Moon to the whole world? links to this humorous video clip of the 1997 comedy movie RocketMan about astronauts on Mars. Personnel on the ground discuss the methane level reported in the space suit telemetry.

I would expect that modern, real space suits report things like temperature, pressure and (possibly) humidity, as well as levels of oxygen and CO2, but what about other trace gasses that might indicate a space suit failure or issue, or a medical condition of the occupant? Ketones, methane, or other byproducts of life processes perhaps?

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    $\begingroup$ If they did and I was an astronaut I'd be a blip on the statistics. $\endgroup$
    – GdD
    Jun 24, 2019 at 13:18
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    $\begingroup$ What is the use of a humidity sensor within a space suit when there is nothing to control humidity? The astronaut is exhaling the breathing gas saturated with water vapor at body core temperature, so the suit atmosphere will not be too dry after some minutes of activity. Methane is not toxic, if it is impossible to accumulate more than about 1 % (no risk for ignition or explosion) within the suit, you need no sensor for it. $\endgroup$
    – Uwe
    Jun 24, 2019 at 15:42
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    $\begingroup$ Note that there's very little methane in human farts, which are mostly nitrogen from air that got mixed in with your food while you were chewing and swallowing. And, while we're on the subject, cows' guts do a lot of fermenting so they produce a lot more methane, but it's mostly belched rather than farted. $\endgroup$ Jun 24, 2019 at 17:01
  • $\begingroup$ @DavidRicherby cite your source (seriously); here's mine: youtube.com/watch?v=l5GDLGaaL80 (lower your volume first) and en.wikipedia.org/wiki/Fart_lighting $\endgroup$
    – uhoh
    Jun 24, 2019 at 17:13
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    $\begingroup$ @uhoh Suarez, Furne, Springfield and Levitt, Insights into human colonic physiology obtained from the study of flatus composition, Gastrointestinal and Liver Physiology, 272(5):G1028-G1033, 1997. Three of the 16 subjects passed about 25% methane, but eleven passed less than 0.01%. On average, the major components were CO2 (34.7%), hydrogen(!) (34.3%), nitrogen (22.2%), methane (5.6%) and oxygen (3.3%). So I was wrong about nitrogen, but most people seem to have almost no methane. $\endgroup$ Jun 24, 2019 at 17:56

1 Answer 1


The US's only "modern, real" space suit, the Extravehicular Mobility Unit (EMU), was designed in the 1970s. It has a very limited sensor suite and no automation at all.

The only sensors used in the suit are

  • A biomedical harness (with electrocardiograph electrodes)
  • A carbon dioxide (CO2) partial pressure sensor
  • A total pressure sensor
  • ventilation flow sensor (an on/off sensor)
  • feedwater supply pressure sensors
  • feedwater pressure sensor
  • O2 tank pressure sensor
  • secondary oxygen pack pressure sensor
  • sublimator outlet temperature sensor
  • battery voltage
  • battery current
  • motor RPM and voltage
  • switch positions

There is also a purely mechanical total pressure gauge.

enter image description here


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    $\begingroup$ Note that astronauts don't tend to spend prolonged times in space suits so the risk of asphyxiating on their own farts is extremely unlikely. Even back in the Apollo days, crew members didn't wear helmets or gloves while inside the CM. $\endgroup$
    – user21233
    Jun 24, 2019 at 14:14
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    $\begingroup$ @Snow the longest EVA I'm aware of was just shy of 9 hours (Voss & Helms, STS-102) $\endgroup$ Jun 24, 2019 at 14:34
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    $\begingroup$ Still, it would take a pretty extreme stomach complaint to raise the stink levels to fatally toxic amounts on an EVA of that length... $\endgroup$
    – user21233
    Jun 24, 2019 at 14:52
  • $\begingroup$ Wow I am really surprised! So the only telemetry potentially available about the astronaut's conditions (excluding self-reporting) is total pressure and CO2 partial pressure, and the astronaut's EKG. Is the "sublimator outlet temperature sensor" measuring the temperature of cold air or water being returned to the suit, or the water vapor being sublimated into space? $\endgroup$
    – uhoh
    Jun 24, 2019 at 15:20
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    $\begingroup$ @uhoh it's the temperature of the cooling water as it exits the sublimator (p. 3-22 in the linked reference) $\endgroup$ Jun 24, 2019 at 16:32

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