FYI, this is for a very short story called Human Error (5 min read)

UPDATE (constraints):

  1. I only have control over the label.
  2. It's a plain old printed label on a physical control panel. You can completely replace the existing printed label with your own. (This is for a sci fi story about UX. The character can only modify the label)
  3. Label should be 4 words (35 characters) or less. Shorter is better.

How would you label an indicator light so it conveys:

"This valve is working properly"

So that if the light went out its obvious the valve was not working properly.


  • Working
  • Nominal
  • Power
  • What technology do you have access to for the indicator? Is it an single LED light or an LED display showing multiple letters or a backlit sign or something else?
    – Raiyan
    Commented Sep 13, 2020 at 12:02
  • Just make it a 👍.
    – Ali
    Commented Sep 15, 2020 at 11:40

3 Answers 3


I'd have a gauge ( even just one with a series of leds which light up).

You want to show an actual measure of something.

Not an indication that something has been told to work, but a measure that it is actually working.

How you design this does also depend on the size of the bang if this valve fails. ( cf the Three Mile Island nuclear disaster).


How about "Power supply to valve active"

  • You are exactly right. In fact this is a "fix" for the 3 Mile Island disaster. However, I can only modify the label. See update in question. Commented Sep 13, 2020 at 14:49
  • Really you need to go interview the operators as it's an example of Don Norman's 'Designers Model' v "Users Model". How the operators think it works behind the screens may not be how it actually works at all.
    – PhillipW
    Commented Sep 13, 2020 at 17:11
  • They are long gone :). While this is a time travel story, they can't interview the operators. Commented Sep 13, 2020 at 20:08

If you really can only use 4 words and you have to convey the whole meaning, all I can think of is something old school like:


I think 'working' could be replaced with something that signifies 'working correctly' but you'd loose the link to the actual valve. I thought 'serviceable' but I think that word is quite ambiguous (people may interpret to be able to be serviced, rather than serving its function).

Could also go with the opposite but it is based on negatives and could take longer to interpret. Also feels less succinct.


You might also consider changing 'lit' and 'unlit' if it's meant for general use; 'on' and 'off' are more easier understood to those who have limited language (e.g. new speakers). However 'lit' relates closer to the lamp itself, meaning users are less likely to get confused by the terminology and relation between the lamp and label.


I'd chose to highlight the danger or error condition instead of when things are working correctly.

  • Label for normal condition: OK
  • Label for error condition : !!FAILURE!!

In monospace fonts and with different text alignment:




Both labels here are short, one word in each. Capital letters are easier to read. Two labels are visually distinct. Regardless of text alignment and font size. Even from a distance they look different. This helps with recognizing the label without reading letter by letter. The label for error condition is wrapped with "!!" to add an extra layer of distinction. In case a robot or machine needs to "see" this, the image classifier will have a higher accuracy rate because of this.

"FAILURE" is somewhat vague and does not convey much information except that things are not working correctly. The operator might want to see something like "leak", "burst", "overflow", "jam" etc., something that gives more information. In that case, a different word can replace "failure", but the "!!" should remain.

Answer before constraints were known. Keept for the records only.

So my labelling would be "RELEASE VALVE FAILURE" and this would lit up when the valve is not working correctly.

In most places of the world, green means OK and red means Danger. But let's not assume that is the case everywhere. Depending on the culture of the operator (or whoever needs to see this) an appropriate colour should be chosen. Let's say our operator reads red as danger. So a red indicator should be lit up when the valve is not working correctly.

If we are not constrained to have indicator for only one situation, I would suggest indicators for both OK and danger situations. Again, say the operator reads green as OK. Then a green indicator light can be used to signal that the valve is working correctly. This has the added benefit of being readable at all times even in darkness. Also, if the indicator is placed close to the valve or the interface to control it, we readily know where to go and start examine or pull a lever.

Edit1 As pointed out by PhillipW, only changing colours for signalling OK/Danger does not help users with colour blindness. Distinct symbols or lettering can help in this case. But it's not clear from the question whether we are constrained to using a single indicator light. If LED letter display or lit up sings (e.g. emergency exit signs) are available, the solution can be improved.

Edit2 Changed answer in response to clarification. Only label text can be changed and has to be within 35 characters, 4 words.

  • The trouble with red and green is that of red / green colour blindness which affects a more than trivial % of men. en.m.wikipedia.org/wiki/Color_blindness
    – PhillipW
    Commented Sep 13, 2020 at 8:31
  • @PhillipW Very good point. This is why I prefer to have lettering or clearly distinct symbols instead of just colours for signalling different states. It's not clear from the question whether LED letters or lit up signs are available in this case. If Clay can clarify this, I'll edit my answer.
    – Raiyan
    Commented Sep 13, 2020 at 13:57
  • Great answer! However, I can only modify the label. See update in question for why that is. Commented Sep 13, 2020 at 14:50
  • @ClayNichols doe that mean you are allowed to change the text entirely?
    – Raiyan
    Commented Sep 13, 2020 at 14:53
  • @Raiyan yes, you can overwrite the label with new text, completely replacing existing label. Commented Sep 13, 2020 at 15:01

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