keihou ga nattara, sugu hizyouguti kara hinansimasu.

• 警報 = けいほう
• 鳴ったら = なったら
• すぐ = すぐ
• 非常口 = ひじょうぐち
• から = から
• 避難します = ひなんします

So the full sentence is read:

けいほう が なったら、すぐ ひじょうぐち から ひなんします。

が marks 警報 as the thing that does the verb 鳴る.

• 警報が鳴る = the alarm sounds
• The alarm is the thing that rings/sounds, so が is natural.

If you used は, it would sound more like you are setting 警報 up as the topic:

• 警報は鳴ったら...

That is less natural here. In this sentence, the speaker is simply identifying what happens first: the alarm sounds.

～たら is a very common way to say if/when after something happens.

• 警報が鳴ったら = if/when the alarm sounds
• It strongly suggests sequence: first the alarm sounds, then the evacuation happens.

Compared with the others:

• ～と can sound more automatic or general: when X happens, Y happens
• ～ば is more formal or conditional
• ～たら is very common in everyday Japanese and works well for instructions like this

So 鳴ったら fits the idea of once the alarm goes off, do the next action immediately.

This is a very common beginner question.

In ～たら, the た-form is part of the grammar pattern. It does not mean the whole sentence is past.

• 鳴ったら literally comes from 鳴った + ら
• As a pattern, it means if/when it has sounded, or more naturally in English, when/if it sounds

So the past-looking form here is not really a past-time statement. It is just how the conditional pattern is built.

In Japanese, 鳴る is an intransitive verb. It means something sounds/rings on its own.

• ベルが鳴る = the bell rings
• 警報が鳴る = the alarm sounds

The transitive partner is 鳴らす, which means to ring/sound something.

• ベルを鳴らす = to ring the bell
• 警報を鳴らす = to sound the alarm

So in your sentence, the alarm itself is sounding, so 鳴る is correct.

すぐ means immediately / right away. Here it modifies 避難します.

So:

• 警報が鳴ったら、すぐ避難します。
• When the alarm sounds, evacuate immediately.

Its position is fairly flexible, but it usually goes before the verb or before the part you want to emphasize:

• 警報が鳴ったら、すぐ避難します。
• 警報が鳴ったら、非常口からすぐ避難します。

The first version is the most natural and simple.

Yes, から basically means from, but in English this sentence is often translated more naturally as through or out of the emergency exit.

• 非常口から避難します = evacuate via / through / out of the emergency exit

Japanese often uses から for the place you move out from or pass through as your route.

So although from is the basic meaning, the natural English idea here is:

• evacuate through the emergency exit

Sometimes other particles are possible, but they change the nuance.

• 非常口へ避難します = evacuate toward/to the emergency exit
  
  • focuses on destination
• 非常口から避難します = evacuate through/from the emergency exit
  
  • focuses on the route used to get out

非常口を避難します is not natural here.

If you wanted to say use the emergency exit, you could say something like:

• 非常口を使って避難します

But in your sentence, から is a natural choice because it suggests exiting by that route.

The subject is omitted, which is very normal in Japanese.

Depending on context, it could mean:

• you evacuate
• we evacuate
• people evacuate
• everyone should evacuate

In a safety notice or manual, the implied subject is usually the people hearing or reading the instruction. So in natural English, it often comes across as:

• Evacuate immediately through the emergency exit.

Japanese often leaves the subject unstated when it is obvious from the situation.

This is about style and tone.

• 避難します is a polite non-past form
• In instructions, manuals, school rules, announcements, and formal notices, Japanese often uses this style to state what people are expected to do

So it can function like an instruction without sounding like a direct command.

Compare:

• 避難します = formal instruction / rule-like statement
• 避難してください = please evacuate
• 避難しなさい = evacuate! (stronger, more direct)

In English, all of these may end up translated as an instruction, but the Japanese tone is different.

It can mean either, depending on context.

• In pure grammar terms, ～たら can mean if or when
• In a safety context, when is often the more natural English translation

So:

• 警報が鳴ったら、すぐ非常口から避難します。

is often understood as:

• When the alarm sounds, evacuate immediately through the emergency exit.

But grammatically, if the alarm sounds is also possible.

The comma is not strictly required, but it is helpful.

• 警報が鳴ったらすぐ非常口から避難します。
• 警報が鳴ったら、すぐ非常口から避難します。

Both are understandable. The comma makes the sentence easier to read by separating the condition from the main action:

• When the alarm sounds, evacuate immediately...

So the comma is natural and useful, especially in written instructions.

No, normal Japanese is usually written without spaces.

The standard writing would be:

警報が鳴ったら、すぐ非常口から避難します。

Spaces are often added in teaching materials to help beginners see the parts more clearly. They are a learning aid, not standard spelling.

Yes, it is understandable and natural enough, especially in a textbook or simple instruction context.

That said, in real emergency signs or announcements, you might also see more direct wording such as:

• 警報が鳴ったら、すぐに非常口から避難してください。
• 警報が鳴ったら、直ちに避難してください。

Your sentence is still good Japanese. It has a slightly rule-like or instructional feel because of 避難します.