Nel caso vediate del fumo, premete il pulsante d'allarme.

Because nel caso often introduces a clause that uses the subjunctive in Italian.

• vedete = you see / you are seeing (indicative)
• vediate = that you see (present subjunctive)

So Nel caso vediate del fumo means In case you see smoke.

This is a common pattern in more formal or written Italian:

• Nel caso abbiate problemi... = In case you have problems...
• Nel caso sia necessario... = If necessary...

In everyday speech, some speakers may also say se vedete, which is simpler and more direct.

Nel caso means in the event that, if, or in case.

It is a more formal expression than plain se.

So:

• Nel caso vediate del fumo = If you see smoke / In case you see smoke
• A less formal alternative would be Se vedete del fumo...

In safety instructions, notices, and official language, nel caso sounds very natural.

Premete is the imperative form for voi of the verb premere = to press.

So it means:

• Press! when speaking to more than one person
• or, in public instructions, Press addressed to readers in general

Examples:

• Entrate = Come in
• Aspettate = Wait
• Premete il pulsante = Press the button

In signs and instructions, Italian often uses the voi imperative because it addresses the public collectively.

Yes, grammatically it is the second person plural: you all.

In practice, on notices and safety signs, this plural can be used even when the message is meant for any reader. It is not necessarily imagining a group standing there together; it is just a standard public-instruction style.

If it were singular informal, it would be:

• premi

If it were singular formal, it would be:

• prema

If it were plural, as here:

• premete

Del fumo is a partitive expression, meaning some smoke.

• fumo = smoke in general
• del fumo = some smoke

In this sentence, the idea is not smoke in the abstract, but if you see some smoke / any smoke.

This partitive construction is very common in Italian:

• vedo del pane = I see some bread
• c'è dell'acqua = there is some water
• ho comprato del formaggio = I bought some cheese

You may sometimes hear just fumo, but del fumo sounds very natural here.

D'allarme is a contraction of di allarme.

So:

• il pulsante d'allarme = the alarm button
• literally: the button of alarm

This happens because di + a noun beginning with a vowel often becomes d':

• un bicchiere d'acqua = a glass of water
• una sirena d'allarme = an alarm siren

So pulsante d'allarme is just the normal Italian way to say alarm button.

Yes. A very common alternative is:

• Se vedete del fumo, premete il pulsante d'allarme.

This means the same thing in a more straightforward way:

• If you see smoke, press the alarm button.

The difference is mainly in tone:

• se = simpler, more direct, very common
• nel caso = a bit more formal, typical of instructions, notices, and official wording

The comma separates the condition from the main instruction.

• Nel caso vediate del fumo = the condition
• premete il pulsante d'allarme = the action to take

So the comma works much like in English:

• If you see smoke, press the alarm button.

It helps readability, especially in formal or instructional language.

The word order is very standard for an instruction with a condition:

• Nel caso vediate del fumo = first, the condition
• premete il pulsante d'allarme = then, the instruction

Italian could theoretically rearrange parts, but this order is the clearest and most natural for a warning or safety notice.

It mirrors the logic:

1. If this happens...
2. do this.

It comes from premere, which means to press.

Yes, it is very common in instructions involving buttons, switches, keys, and controls:

• Premere un pulsante = to press a button
• Premete invio = Press Enter
• Premere il tasto rosso = Press the red key/button

So premete il pulsante d'allarme is exactly the kind of phrase you would expect in a manual, building notice, or emergency instruction.