First of all I'm completely against this idea but a few people who contribute to the technical documentation project constantly suggest that to attain a short, quick, economic, comprehensive message some basic rules can be broken. Things like completely omitting the articles, using simpler words to explain things, using the imperative mode to shorten verbs, even tossing out basic grammar rules etc.

Are there some rules of thumb or even legal directives about the language of machine safety labels?

I'm citing a few examples of text written by those outsiders and my suggested corrections to make my case more clear:

Do not open this cover while powered
Do not open this cover while the machine is powered

Ensure power is disconnected before servicing
Ensure that the power is disconnected before servicing the machine

Do not clean the machine using water or materials that can generate an explosive atmosphere
Do not clean the machine using chemicals that can generate an explosive atmosphere or using water that can create an electric shock


Thanks for your answers. I mostly conclude with every answer but I have to apologize to all of you because I think I did mislead you by not presenting my case in detail. I'll give more details even if it's a little bit late.

We manufacture big machines which have too much surface area and therefore our labels have too much space for details, too. We have 4 kinds of labels:

  • There are informational labels which are used to designate the inlets (The type of the heating power such as steam or gas and the water inlets), the power switch, and the grounding connection quickly and precisely. Those inlets are also designated on the installation layouts and projects, so these labels are not the only markers of these inlets. They are there mostly to quickly remind the authorized personnel of their functions. They just include the 1 or 2 words describing the inlet type, a pictogram for it and if it's necessary the pressure limits of the heating supply.

I don't have any problems with these labels.

  • There are two purely graphical labels which don't have any words on them. They only show the rotation direction of the blades of a fan and the bolt locations of the safety belts which have to be unbolted after the installation phase.

I don't have any problems with these labels, too.

  • There two legends for the explanation of the status light patterns and the explanation of the abbreviations used on the simpler model of the control panels that we are using.

Again, I don't have any problems with these labels.

  • There are the safety and information labels. We've designed the labels to include as much information as possible but at the same time to display this information in a practical and useful manner. Most of these labels include an internationally valid pictogram, a word describing the message type of the label in colored background and big fonts (Information, Warning, Caution, and Danger), a title of the label in very big fonts (which corresponds to the content that most of you were answering) and the details of the title message in either just one font size or sometimes if the message details are too long in two different font sizes.

I mostly don't have any problems with the title of our labels. They are the type of labels which most of you did mention in your answers.

My problem is with these detailed text parts of our labels. I'm including a screenshot which contains four types of our safety and information labels so you can clearly see how they are constructed.

I'm aware that most of your answers can still be valid for them, too. I'll try to be more open minded when dealing with them in the future but I'll wait for your reactions to the detailed edit to my question before accepting one of your answers

Note: These label are printed on a transparent material which is the reason for different font colors. The ones with black fonts are meant to be fixed on light colored panels whereas the ones with white fonts are meant to be fixed on dark colored panels to enhance the readibility.

Thanks again.

safety and information labels

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    As a part-time safety consultant: High signal-to-noise ratio saves lives!
    – corsiKa
    Commented May 27, 2016 at 22:29
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    In the last one, even if you don't change it the way you suggested, at least add a comma between "water" and "or". Commented May 28, 2016 at 1:03
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    "...using simpler words to explain things..." That's not breaking any grammar rules. That's writing for a wide audience, and completely appropriate for warning labels. Commented May 28, 2016 at 7:29
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    I've even seen "Ensure power disconnected before servicing" The "is" is redundant. Commented May 29, 2016 at 7:08
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    Grammar is a construction of usage. This can make it contextual. What you've identified is that warning labels are such a context. It's not that they don't have a grammar. They don't follow the same grammar as a either a business letter, as a legal document, or of a text message. Least I've never seen an emoji on a warning label. If it has rules that can be violated it's a grammar. Commented May 29, 2016 at 17:25

12 Answers 12


Of course you can't just ignore all basic grammar rules. For example, writing:

Not cover the opening machines power be while do.

obviously makes no sense to anyone, even though it's got all the right words (plus or minus a few grammatical suffixes) in there. It's just broken English.

But you can totally write, say:

Do not open cover while machine is powered.

or, if space is really at a premium (or you just want to make the letters as big as possible to make them stand out), e.g.:


So what's the difference, then? The difference is that, in effect, English has a special linguistic register for terse messages like signs and headlines that modifies or relaxes some otherwise (nearly) universal grammar and style rules in the interests of brevity. But not all rules; only those that do not introduce any significant ambiguity in the message (or for which an alternative method for conveying the same distinction is available). In effect, it's a different language variety with (somewhat) different grammar rules from general literary English — but it does still have grammar, because a language with no grammar at all is not a language, but just a bunch of random words thrown together.

So what are the differences between general English and this "headlinese"? I haven't personally read any scholarly studies on the grammar of this special language register (although it has been studied, and the Wikipedia page I linked to even references a couple of articles on the subject), but just off the top of my head, the most notable differences are:

  • Omission of definite and indefinite articles. When you really think about it, articles are rarely essential for conveying the meaning of a sentence. Plenty of languages get by just fine without them — the map on the linked page shows pretty strikingly that the (near) compulsory use of articles in front of nouns is a distinctively Western European areal feature. In many languages it's a relatively modern one, too; classical Latin didn't have articles, but most of the Romance languages that descended from it developed them (generally from demonstrative pronouns that became a compulsive part of the noun phrase) under the influence of neighboring Germanic languages.

  • Omission of the copula. Have you ever seen a sign that said "Door is closed," or a headline that read "Politician is caught lying"? Again, plenty of languages get by just fine without a copula at all, anyway.

  • Use of stand-alone noun phrases instead of full sentences. Related to the above, it's very common to replace sentences that in standard English would use the copula "is" with just a plain noun phrase (with, effectively, an implied "there/this is"). This is very common in signs: "NO SMOKING", "WET FLOOR" or "OUT OF USE" communicate their ideas much more concisely than "Smoking is not allowed here," "The floor is wet" or "This machine is not currently usable."

  • Omission of implied referents. The default assumption is that a sign refers to the object or the location it's attached to. Thus, you don't need to write "This store is closed" or "No trespassing on this property." Of course, such omission also occurs in standard literary English (even if some grammarians frown upon it), but it's extremely common in signs.

There are also some grammar and style features that, while not directly serving the interests of brevity, have nonetheless come to be commonly associated with this particular style of English. A notable example is title case, which (as the name indicates) is very popular in titles and headlines, but also commonly found in other places that employ a similar terse style. (Exercise: Open a drop-down menu on your computer and look at the entries; there's something like a 50-50 chance that they'll be In Title Case.)

Anyway, my point is that, as long as you follow the established style and grammar conventions relevant to the context you're writing in, you certainly can (and, arguably, even should) break any "rules" of prescriptivist "standard English grammar" that conflict with actual established usage in your field. That's not the same as throwing grammar, willy-nilly, out of the window — that's just understanding that grammar, like all things in human communication, is a context-dependent and flexible construction that can and does adapt to fit the needs of the medium.

  • 2
    This - English (and other languages) has a lite version that's grammatically correct and unambiguous. Just use that. Quality check it to make sure it's clear - maybe create long versions that can be reviewed e.g. by (potential) users.
    – Michael
    Commented Jun 2, 2016 at 14:47
  • In some cases, a positive action is more direct and helpful than a negative (don't do this) action: TURN OFF POWER BEFORE OPENING. Or, UNPLUG POWER CORD BEFORE OPENING.
    – user8356
    Commented Sep 27, 2021 at 18:56

I really like this question. I cringe to say it, but I somewhat agree about breaking grammar rules in the interest of safety. I frequently write technical emails/IT system announcements that are sent out to a large group of non-technical people and I find that if I write the emails using the same language that I'd write in my short stories, or even my technical diagrams, then nobody will read them.

Machine safety labels - any safety labels - need to get to the point... Right Now! The fewer words the better, and the simpler the better because you're working to do two things:

  1. Keep people from getting hurt.
  2. Keep the company from getting sued because someone got hurt.

I'd love it if safety labels were grammatically correct, but I think they just wouldn't be as safe then.

Dear Sir/Madam,

Please do not touch the violently spinning wires in the wire rope machine in front of you as they may cause certain parts of your body to become separated from the rest of your body, or in the event that your different body parts do not separate, your whole body may be pulled into the machine. Either way, a gruesome, bloody, painful death will occur and everybody will be sad.

Thank you, and good luck.


Edit: If you're looking for specific legal advice about this... I'm just a writer and a computer geek... You should ask your company's lawyer and then write the labels whatever they say is the correct way. Your lawyer is going to have specific knowledge about your industry and about the risks involved and will probably be quite happy to put in their two cents.

  • 13
    In other words: "The people reading them are not complete idiots. You are reminding them of something they should already know, not writing a manual."?
    – Sumurai8
    Commented May 27, 2016 at 16:36
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    Exactly. Either they already know it and need a reminder, or they haven't learned it yet and need to be warned there's danger here and they should find out what the danger is, or there's an obvious danger that the company has to warn people about because they'll be responsible for damages if they don't. Does the warning not to put a plastic sack on your head actually keep people from doing it? Probably not, but since it's there, the company that made it can say they did what they could to keep the thing from being used improperly.
    – DoWhileNot
    Commented May 27, 2016 at 16:59
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    "Do not look into laser with remaining eyeball." Commented May 28, 2016 at 2:04
  • DoWhileNot and @LaurenIpsum Thanks for your Douglas Adamesque safety labels :) You've made my day. I wish I could write in that language :)
    – Montag451
    Commented May 29, 2016 at 14:43

The label should be as short as possible without creating ambiguity.

In many workplaces, the employer is required (OSHA, ISO, FDA, etc.) to train anyone who would be working in a particular area with the hazards of the environment and the equipment. The label acts as a reminder (as well as a legal obligation). Everyone in that lab knows lighting a flame near the hydrogen hood is a bad idea. Anyone entering that lab should require safety training.

If the labels you used as examples are positions such that there is no ambiguity as to which system has to be turned off or which cover can't be opened, then clarify. If it's clear, don't add additional wording. If the label is on the wall, then, yes, it should specify you're talking about the spectrophotometer with the yellow cover.

If you are working in a small business that is not government regulated, then the need for more explicit labels may be required.

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    For example: orig11.deviantart.net/3d37/f/2010/234/e/d/…
    – Milo P
    Commented May 27, 2016 at 19:42
  • Yes, most of our safety labels are intented for specific locations on the machine (only the informational ones being the exception). We even have 2 separate pages in the operating manual which include the locations of the labels and their label number and content style guides.
    – Montag451
    Commented May 29, 2016 at 14:49

I'd say yes, but ... not if it loses clarity.

Warning labels have to be concise or people won't be able to read them, or won't bother to read them.

For example, a label that says "HIGH VOLTAGE" expresses the warning very briefly and concisely. Yes, it's not a complete, grammatically correct sentence. But you can write it in big letters so people can it from far away. It takes a fraction of a second to read it so they get the message.

Sure, you could write a more thorough explanation. "This machine has a variety of electrical and electronic components. If you were to touch bare wires, either with one hand on each of two separate wires, or a hand on the wires and your feet touching the ground, this might make it possible for electrical current to pass through your body, which can have adverse consequences on your health ..." etc. Would that be better because it uses complete sentences? Obviously not. Yes, that was a ridiculous extreme.

At the opposite extreme would be warnings that use incomplete sentences and invalid grammar in a way that makes them ambiguous. Like suppose someone posted a warning that read "DANGER RED BUTTON". Does that mean that it is dangerous to touch the red button? That you should push the red button when you believe that something dangerous is happening? That the button lights up or something when there is danger? It's hard to say because the warning has been abbreviated too far.

To take one of your examples:

"Ensure power is disconnected before servicing" versus "Ensure that the power is disconnected before servicing the machine"

I don't see how "that the" after "ensure" adds anything or clarifies the meaning. It's easily left out for brevity. Likewise, what does adding "the machine" help? Of course we mean "servicing this machine here that the label is on". As opposed to what? Servicing a customer's charge account? I suppose you could imagine someone thinking that you mean servicing the power supply. But the power supply is a machine too, so specifying "the machine" doesn't clarify the only remotely plausible alternative reading. Thus, I conclude this one is fine the way it is. The meaning is about as clear as it's going to get.

The one about cleaning with water is debatable. Someone might think it means that cleaning with water can generate an explosive atmosphere. That's not irrational: Perhaps chemicals can leak out of the machine, and if you put water on them, the chemicals react with the water. Or some such scenario. You'd have to know a lot about the machine and how it works and the environment that it's in to say, and if you knew all that, you wouldn't need the warning label.

  • Perhaps the button lights up green when there's no danger and red when there is danger. Commented May 28, 2016 at 1:04
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    @immibis: ...presumably to help keep down the prevalence of red-green color blindness in the gene pool. :P Commented May 30, 2016 at 8:13
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    @IlmariKaronen Those who are red-green colourblind would know to look around them for danger instead of staring at the button. Commented May 30, 2016 at 20:24
  • For "Ensure power is disconnected before servicing", your comments are spot-on, I fully agree. But the sentence still has a problem: the immediate object for "servicing" is "power". Of course anybody will discard that interpretation and notice that "servicing" refers to "the machine", semantically. But that takes time, even if milliseconds. Or at least brain power, some tiny distraction. Perhaps "Before servicing, disconnect power"...? [OTOH, going against the-usual-safety-label-style also risks that moment of distraction...]
    – Pablo H
    Commented Sep 14, 2021 at 16:03

The only rules you should feel free to violate are the rules about having a subject (which is implied), and possibly the trailing period of the sentence. All of the remaining rules should apply. For example, these three sentences from your examples should be logical enough for the average human.

Do not open while powered on

Disconnect power before servicing

Do not clean with water or explosive chemicals

Note that in all three cases, there is no subject. The subject is implied by label placement: we can (and usually do) naturally assume that the label is intended for the device it is affixed to. Also, we don't generally say why you shouldn't do something, partly because it's usually obvious (e.g. power is usually shocking, explosive chemicals tend to... explode), and partly because we don't want to have people trying to do risk assessment without proper training. A trained professional may choose to violate the warnings because they know what can go wrong, how to avoid things going wrong, and how to minimize damages when things go wrong.


While I understand that space can be at a premium with these labels, I will always, always come down on the side of clarity. Warning labels frequently get turned into jokes precisely because the originators thought that words could be dropped.

Do not open this cover while powered

My thought: While the cover is powered? So as long as I unplug the cover, I can leave power on for everything else?

The second one is probably okay.

Do not clean the machine using water or materials that can generate an explosive atmosphere

My thought: Water can generate explosions?!

so yeah, I'm with you. Clearer is better.

  • 3
    I like your answer - and I kind of agree with it even though my answer says the opposite thing... This is a really great question! I guess the answer might be somewhere in between. Yes, being clear is important, but so is the imperative to stop and think before something bad happens.
    – DoWhileNot
    Commented May 27, 2016 at 16:05
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    I sort of disagree here. Clarity is important, but simplicity is equally important. Fewer words are fewer things that need interpretation. Simple clarity should be the ultimate goal. There's a reason that a stop sign just says STOP and not "Stop temporarily to check for traffic which may be crossing your path". Safety stickers need not be reference manuals - they need to simply convey an immediate need for caution (to make the user think "If you're not sure, don't do it"), and (ideally) the nature of the danger. The former is much more important than the latter.
    – J...
    Commented May 28, 2016 at 20:03
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    To use your first example (I know you were being humourous, but for the sake of argument) - if a person didn't understand whether or not the power was supplied to the cover, the danger sticker should at very least make them wary enough to understand that their lack of understanding should be reason enough for them to be careful and not proceed without a more exhaustive consideration of the hazards they intend to expose by going any further.
    – J...
    Commented May 28, 2016 at 20:07
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    I'm completely on your side but after reading most of the answers (which I already knew from my fellow content contributors) I'm thinking of lighting up my conservations a little bit.
    – Montag451
    Commented May 29, 2016 at 15:09
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    "... while powered" is of course short for "... while you are powered" :) Commented May 29, 2016 at 18:08

Yes, absolutely you can throw grammar rules out the window. Machine safety labels need to convey the danger clearly first and foremost. They also need to consider that the audience may not be fluent or conversant in the language at all. Grammar is largely irrelevant, and simple is always better.

As example, here are a collection of safety labels from some Japanese made equipment (installed in North America). I've not included the awkwardly translated text from some of them, and for many it's not even the grammar that's the worst part so much as the vocabulary itself. That said, strong iconography makes the point quite clear in all cases. The wording itself plays second fiddle, really.

machine safety label catch/pinch machine safety label suffocation machine safety label explosion machine safety label falling machine safety label heat/press machine safety label no standing machine safety label pinch/press

  • 2
    you make two excellent points: consider the potential language barrier of the audience, and a good icon is worth a thousand words. Commented May 28, 2016 at 18:25
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    Ouch... the kerning... Commented May 31, 2016 at 1:43
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    @NeilFein PRESS is kerning... BE WARE is, I think, a deliberate whitespace lost in translation 0_o
    – J...
    Commented May 31, 2016 at 1:54
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    Also note that, given the strong iconography, the Japanese decided that はさまれるな (Do Not Be Sandwiched) was sufficient for both the PRESS and ENTRAP warnings while their English counterparts felt deserving of unique words. A testament, I guess, to how particular English speakers are about finding exactly that correct phrase to fit the occasion.
    – J...
    Commented Jun 1, 2016 at 3:39

Your question specifically asks for grammar, but perhaps you might consider distinguishing grammar and punctuation. Punctuation is variable for clarity, also known as typesetting, while grammar is more or less fixed.

Punctuation: commas, periods, exclamation points ...

Grammar: Grammar consists of the rules governing how words are put into sentences. [The Chicago Manual of Style 5.1]

For instance,

  1. Do not place finger in nose.

  2. Not place finger nose

  3. Don't place finger in nose!

  4. Yo! Nosepicking ain't cool, dude

What I like about (1) is the proper use of grammar AND the use of a period. Over time, warning labels get smudged, burned, drawn on, etc. When you complete a sentence, imperative or otherwise, use a period--we know a thought has been completed even if a word is smudged.

(2) is an example of improper grammar. I don't think you can get away with any grammar mistakes and achieve the clarity you're looking for. To the extent you can leave out articles, that, then, pronouns, and certain auxiliary verbs does not make for improper grammar--I mean, makes not for improper grammar.

(3) I think contractions are OK. Someone who has such poor conception of English to misunderstand probably needs a label in a different language. However, I'd recommend only using an exclamation point once per label or maybe twice, but even then, CAPS or bold may be a better choice for the most important thing.

(4) Stay away from idioms! Period.


In support of @DoWhileNot, the words "No Step" is placed on almost every airplane wing. It's bad grammar, but gets the point across to even the most basic English speaker/reader.

Though, when I first read it, I was very confused... looking for faded or missing words that may have fallen off.

enter image description here

  • 2
    The first time I saw "NO STEP" on an airplane wing I read it as a 'sign grammar' abbreviation of "I have designed, built, and encountered many steps in my long life, and this, young man, is no step." Commented May 30, 2016 at 16:02

This is the beauty of the English language. It can convey a greater meaning from the individual parts even when some words are omitted, or grammar is truncated.

The clue is that good warning language or brief instructions should be written so that the reader can infer the meaning. And if you look closer very often you can fill in the blanks and then you have a complete sentence.

Airplanes are a perfect place to see or hear signs, placards and brief messages.

Fasten seatbelt while seated

No smoking

Doors to manual and cross check

Prepare for departure

Prepare for take off

Flight attendants be seated

and of course the best of them all NO STEP meaning do not step here or do not place your foot/step here

  • 1
    Here's a good example of "too much omitted": Doors to manual and cross check. I have no idea what that means out of context, particularly without a hyphen in cross check: Does that mean "cross-check the doors with something"? Are "manual," "cross," and "check" three settings? Do I cross off something with a check? This is industry jargon, so I'm sure the flight crew understands it, but as a lay person, I don't. Commented May 29, 2016 at 14:59
  • @LaurenIpsum: True, but since the sign is meant for the flight crew, that is presumably not a problem. Commented May 29, 2016 at 18:22
  • Unless "no step" means it's skipped in the checklist.
    – JDługosz
    Commented May 30, 2016 at 5:05
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    @LaurenIpsum - before you manually open this door, check that you're still wearing a cross for protection.
    – Joe
    Commented Jun 1, 2016 at 2:44
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    @Joe oh, of course. I'm an atheist; no wonder I didn't understand that one. Commented Jun 1, 2016 at 9:37

I think one significant problem boils down to this attitude


More-so a problem with the younger generations; there's a perceived coolness around not-learning. Also, reading words is more cognitive load than simply recognising a (good) pictogram or even identifying a colour.

So in this case, less is more and fewer words leads to better outcomes. If grammar suffers, then at least waffle is decreased and signal-to-noise ratio increases.


"Doors to manual and cross check"

Good example of brevity, IMO. The instruction is not supposed to replace the cabin crew training course, nor explain aircraft operations to passengers, but to remind the target audience (the cabin crew) with a few essential words what they need to do.

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